# Forum Home Renovation Roofing  COMPLEX roof - HELP! - Hip end with offset partial octagonal

## ChipperChip

Howdy all.. 
I never did an apprenticeship, and I'm about to pitch my first roof. Well, I did a trussed gable end roof for a run of bike sheds in the UK, but that was just like leggo. I feel like I'm going from sandcastles to skyscrapers in one step. I'm not scared exactly, but close. You'll see why. It's taken me ten revisions of the pitching diagram to get to this point, so I understand the shape well - forgive me if I dont convey it well! 
This is a stick built coupled roof being done as part of an extension and renovation. There is a bunch of steel work in the new framework, and some complexities added by a very low ceiling height and local planning height restrictions. I've got my head around most of it, but I'm struggling with how to construct the area around the short minor ridge, and the very long shallow broken hip associated with it (running WNW of the octagonal part's peak). I can't get any full common rafters onto the minor ridge at all! 
The drawing attached shows the plan view with the proposed hip, valley and ridge locations. It doesn't show internal walls, but the SW corner is BR2 and the octagonal roof is over BR3. The existing roof is to the north and we are extending it to the south, with a hip end, and the octagonal area intersects what would be the south-east corner of the hip end. 
The line A-A' shows the approximate line of the original hip end's fascia. The extension south of this point has a 190mm step in the floor, and a corresponding step in the ceiling. However, local planning rules mean that on the west face we can't have either eaves or a higher fascia line. So, the SW corner (BR2) has bulkheads on both walls, 190 high and 400 wide, to hide the structural beams shown in that corner (N-S is steel, E-W is timber). We can have eaves on the other side of the building (further from property boundary) so we have them as shown (400 wide) to avoid having bulkheads in the other bedroom (BR3). 
To add a tiny bit more complexity, the extension area is being clad in 75mm polystyrene but the original building is BV, so our top plates step out about 90mm at the change. Thankfully the new rafters are 90x not the old 120x so we can squeeze them in with careful underpurlin placement (span limitation). 
Lastly, the space available for windows in BR3 (octagonal area) meant that our steel lintels (NE, E and SE walls) have no timber plates on top, so everything is being mounted on individually welded cleats. Yay. 
I think I know how to START the setting out, as follows:  
1) find the centre of the octagonal area first (midpoints of the east and south fascias of the octagonal area)
2) find the height of the octagonal area from the known pitch of its northern face (same as existing main roof, 25.5 degrees)
3) find the pitch of the SW face from the height of the peak and the plan distance from the SW fascia
4) find the height of the minor ridge from half of the distance from the S fascia of hip end to the N fascia of octagon, and the known pitch.
5) find plan distance square to SW fascia to point where SW face of octagon reaches height of minor ridge.
6) project this parallel to SW fascia to intersection with minor ridge line. This locates E end of minor ridge/W end of broken hip. 
But, step 6 is going to be kinda awkward in mid air to say the least! 
7) I think I can do ok with the other broken hip (SE from the main ridge) by simply locating where the SE corner theoretically would be. 
That should locate all the relevant geometric lines/pitching points. 
As for the construction steps, given the shallow pitch of the long broken hip, it's almost like a ridge. I'm planning to treat it as such, and then the octagonal roof area can be treated a bit like a hip end, with the NNE and SSW hip rafters behaving like common rafters, and the ESE hip rafter behaving like a centre jack rafter (what's the right term again?). The other hip rafters slot in like 'conventional' hip rafters, although at different pitches. 
My questions to the more experienced out there are: 
1) Am I missing anything in the setting out I've described?
2) What sequence of construction would you recommend? I'm thinking of simply working W to E, but tips like what to temporarily strut, putting in temporary common rafters or whatever would be very useful.
3) I'm not planning to put a central rafter to the peak of the octagonal roof on any of the faces. There is simply no room to move if I do that. Is this a bad idea?
4) I can easily run the rafters square to the fascias, but I'm not enjoying putting in the ceiling joists. Anyone got a good idea there, given that I want them to meet the rafters at the same cleats? Besides, I need tie-in, particularly for the timber SW wall. I've already installed ceiling joists from the W wall of BR2 across to a large strutting/hanging beam that runs N-S in the middle of BR3. They're fixed with joist hangers as the beam is low to stay within chamfer limits at the outside walls. 
Any other gotchas that come to mind would be very very useful. 
This puppy is DEFINITELY going in my CV. 
Cheers,
Grant

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## Ian Smith

Chipperchip,
This is not a answer to any of the myriad of questions you ask. 
In fact I'll be real surprised if:
(a) anyone reads all that you have written, 
(b) understands what you want, and 
(c) bothers to take the time to write, what I suspect will amount to "Roofing 101", in reply.  
Still, maybe someone with the expertise you seek is prepared to take the time. 
One thing that does strike me though is, given you are asking a whole bunch of questions, and given you do get a response to them, wouldn't it be a just a bit cheeky to plonk it on your CV as your own work?? 
Ian

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## rona

Ian,
     I'll answer your comments firstly, you are possibly right in your assumption that no one will respond to Chipperchips request. You cannot have a conventional style house layout then suddenly come up with a way out structure like is drawn-up here.                                                               Chipperchip,                                                                                       
               Firstly you need some elevations, followed by a scaled set out of your intention, what you have there simply is not workable, you have unequal pitches on your rooves, your eaves overhangs will also vary considerably. You made mention of the fact that you did not undertake an apprenticeship, that becomes obvious with your sketch and also your notations for various theories. Not an easy one to solve in its present state, obviously you are doing this as an owner-builder because the building inspector should have pointed things out to you early on. I assume you have not looked at any costings as yet either. 
               Suggestions at this stage are, talk to someone that is prepaired to look at house plans, not an architect, someone who may do weekend work in top end renovations. I cannot possibly hope to outline where to start from my end. 
                Good Luck,
                                Rona.

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## journeyman Mick

Grant,
that's a total brainf**k  :Shock:  . I quite enjoy challenges and helping people on the forums but I've a feeling that Ron is right and thati t's not possible. Do you have proper drawings for this job? If you really mean to go ahead with it I'd suggest telling the client (or yourself if you're going owner builder) to spend the money to get it all drawn up by someone with a 3D CAD program. Get them to do one of those wireframe type drawings that you can view from all angles and see if it is, in fact, possible. It may also show you that it may end up looking like a dog's breakfast. :Shock:   
Mick

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## ChipperChip

Ok, I'll resist the feeling of being talked down to ;-) 
This roof was designed by the architect for this build. I'm the poor sod who's got the job of turning it into a functioning pile of wood and tiles. I've already put this in front of two experienced framing carpenters I know, but unfortunately neither of them have done much coupled roof framing other than repairs and minor mods - their experience has also been almost exclusively in trussed roofs. 
First up, Ian, if you suspect a useful reply "will amount to "Roofing 101"" then I suggest you stick to making furniture and using your triton to rip 2mm slices off the bottom of doors. I hope it was a pretty door mate. Buy yourself a planer. I came here looking for help with a genuinely tricky roof, not abuse from a habitually condescending smart alec.  :Annoyed:   
Rona - Firstly sorry to read about your health, you have my very best wishes. Secondly, thanks for your comments. Whilst I haven't done an apprenticeship, I have been working as a construction carpenter for 5 1/2 years both here and in the UK, doing structural work, framing, fixing, floors, stairs and kitchen fits mostly. No roof framing though. If my terminology is off I blame learning my trade in the UK  :Smilie:  That and being inexperienced with roof framing. For what it's worth I also have a first-year-out qualified chippie from Ireland, a third year apprentice and a second year apprentice on site with me, and I have more experience than any of them with structural work. 
The roof layout is a result of the architect extending the octagonal room below straight up, and this is all on the inspected and planning-approved drawings. The roof we removed before extending up was simply an octagonal roof on the end of an E-W minor ridge - considerably simpler and something I've half built in the past from a friend's trade school notes (I simply didnt have time to devote to finishing it). 
The ceiling height change isn't on the original approved drawings though, as the architect hadn't done a site visit and had missed the step in the existing lower ceiling that has now resulted in the step upstairs, and the beams and eaves. 
Sorry if I've left some stuff out - I was trying to keep clutter on that drawing to a complete minimum. That sketch is actually to scale (CAD output) that I drew up from site measurements - yes, the framing is already up. Attached is a similar sketch showing what the pitches should be. The highest is 27.2 degrees, and the lowest is 25.5. There will be no significant difference in eaves overhangs. I have another showing hip and valley runs. I also have a basic elevation I produced from an earlier proof-of-concept plan, but it would need to be reworked. Do you think it's worth re-doing? Perhaps some sections? 
This roof WILL work, and it will go up substantially as shown - I'm just trying to get some idea on how to do it in less than two weeks  :Cry:  
Where's Pawnhead?  :Smilie:

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## ChipperChip

Mick: 
Yeah, that's the way I felt about it at about revision 5 of my own drawings. This is rev 10 and I feel a whole lot better about it. The pitches work and I can see the wireframe in my head, but I still wish I had a 3D CAD package to actually build it in. 
That said, I know the architect well, and I can get his 3D Autocad as a loaner. I'm keen to draw it up in 3D just for the experience. In a previous career I was an IT Systems Manager for a string of advertising companies, and before that did desktop publishing, so I'm fairly computer literate  :Smilie:  Sadly, it would take me at least three days to get that drawing right and I dont have that time spare to take away from the job.

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## journeyman Mick

Grant,
I had another read of your post, and it's still a brainf**k  :Shock:   :Doh:  . Mind you, it's past midnight and I've had long days lately. Sorry, but the most complex roof I've ever hand pitched was an "L" shaped hip and valley roof at 30 deg. with a verandah surrounding it at 12.5deg. It was all exposed though and all the joints had to be tight and spot on visually. I usually resort to drawing joints out full scale (if possible) on a sheet of ply or a smooth concrete floor when I get stuck. I reckon if it were me building it, I'd be spending more time drawing than marking and cutting. :Blush7:   
Now there's an idea, when doing some boat fitouts I had the engineer print out some details so that we could wrap the around pipe sections to get them shaped right. Theoretically you could get the angles and length of each rafter (well at least the length to the centrline of its adjoining piece) If you did this it would be a bit like a meccano set. 
Mick

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## pawnhead

> Where's Pawnhead?

  I'm here and I'm putting a post together now. It's late though and there's a lot to think about in that one Chipsy. I might not post until the morning.  
You should have no problems if you're capable though. :Biggrin:  
I'll just ask, are they exposed rafters in the octagon? 
edit: - For anyone else, just PM me if you wish to draw my attention to a thread, or ask a question.

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## ChipperChip

Mick, it'd be nice to see that exposed rafter work. Challenging but rewarding I'll bet. I had thought of the whole meccano approach but I dont know that I trust my CAD quite THAT much  :Smilie:  
Maybe one go at cross-checking some dims on my CAD with the real world might get me that confidence. I'll have a look at it Monday because I'm pretty sure the boys wont get that far. (I'm off the tools thanks to a 9" angle grinder taking a liking to my left forearm. I got off lightly thankfully. No major structures damaged, but one big muscle 80&#37; cut. Six weeks off the tools, 2 1/2 to go). 
Pawnhead : thanks for looking at this! No, the rafters are not exposed. It's all coupled, with a ceiling, and the eaves will be enclosed too (hangers and eaves joists). 
Please, if anyone needs more info I'd be very happy to provide it. Doing so will just make me think about it from another perspective and iron out any kinks I might not have noticed. 
Thanks again all. 
ps: I should point out that in these sketches the inner perimeter line is the OUTSIDE of the framing, and the outer line is the INSIDE of the fascia. Fairly unimportant since there aren't any dims, but perhaps it will help people visualise things. This is a *sketch*, people, not a full-on architectural drawing  :Smilie:

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## pawnhead

> Howdy all..

  Howdy Chipsy  

> I never did an apprenticeship,

  Neither did I and I taught myself how to pitch a roof with basic trigonometry skills from high school, and by looking at roofs. I like a challenge so Ill have a look at it. It may be a benefit to anyone reading these forums in future as well.   

> I understand the shape well 

  Is that a scale drawing, because its very wonky. Youll need to start with some accurate ground measurements and you should be able to cut everything on the ground from calculations.   

> This is a stick built coupled roof being done as part of an extension and renovation. There is a bunch of steel work in the new framework, and some complexities added by a very low ceiling height and local planning height restrictions. I've got my head around most of it, but I'm struggling with how to construct the area around the short minor ridge, and the very long shallow broken hip associated with it (running WNW of the octagonal part's peak). I can't get any full common rafters onto the minor ridge at all!

  No problem.  

> The drawing attached shows the plan view with the proposed hip, valley and ridge locations. It doesn't show internal walls, but the SW corner is BR2 and the octagonal roof is over BR3. The existing roof is to the north and we are extending it to the south, with a hip end, and the octagonal area intersects what would be the south-east corner of the hip end. 
> The line A-A' shows the approximate line of the original hip end's fascia. The extension south of this point has a 190mm step in the floor, and a corresponding step in the ceiling. However, local planning rules mean that on the west face we can't have either eaves or a higher fascia line. So, the SW corner (BR2) has bulkheads on both walls, 190 high and 400 wide, to hide the structural beams shown in that corner (N-S is steel, E-W is timber). We can have eaves on the other side of the building (further from property boundary) so we have them as shown (400 wide) to avoid having bulkheads in the other bedroom (BR3).

  Understood  

> To add a tiny bit more complexity, the extension area is being clad in 75mm polystyrene but the original building is BV, so our top plates step out about 90mm at the change. Thankfully the new rafters are 90x not the old 120x so we can squeeze them in with careful underpurlin placement (span limitation). 
> Lastly, the space available for windows in BR3 (octagonal area) meant that our steel lintels (NE, E and SE walls) have no timber plates on top, so everything is being mounted on individually welded cleats. Yay.

  Well you werent joking when you said complex.   

> I think I know how to START the setting out, as follows:  
> 1) find the centre of the octagonal area first (midpoints of the east and south fascias of the octagonal area)
> 2) find the height of the octagonal area from the known pitch of its northern face (same as existing main roof, 25.5 degrees)
> 3) find the pitch of the SW face from the height of the peak and the plan distance from the SW fascia
> 4) find the height of the minor ridge from half of the distance from the S fascia of hip end to the N fascia of octagon, and the known pitch.
> 5) find plan distance square to SW fascia to point where SW face of octagon reaches height of minor ridge.
> 6) project this parallel to SW fascia to intersection with minor ridge line. This locates E end of minor ridge/W end of broken hip.

  That all sounds reasonable, except youre projecting it in line, not in parallel. Im sure you realise this, but Im just a nit picker.  :Wink:    

> But, step 6 is going to be kinda awkward in mid air to say the least!

  Not really. You could pitch it all single handed but it would be a lot quicker with two pairs of hands.    

> 7) I think I can do ok with the other broken hip (SE from the main ridge) by simply locating where the SE corner theoretically would be. 
> That should locate all the relevant geometric lines/pitching points. 
> As for the construction steps, given the shallow pitch of the long broken hip, it's almost like a ridge. I'm planning to treat it as such,

  Its a broken, or flying hip. Its not a ridge.   

> and then the octagonal roof area can be treated a bit like a hip end, with the NNE and SSW hip rafters behaving like common rafters,

  I don't know why you'd call them commons. They're bastard hips and they will have to be calculated or measured.   

> and the ESE hip rafter behaving like a centre jack rafter (what's the right term again?). The other hip rafters slot in like 'conventional' hip rafters, although at different pitches.

  Theyre all bastard hips according to that wonky drawing. Theyre not the same dimensions as each other either as you realize. Theyre all bastards and it might be easier to measure rather than calculate, after youve got the basic pitches set. Im still thinking about the easiest way to pitch it.   

> 4) I can easily run the rafters square to the fascias, but I'm not enjoying putting in the ceiling joists. Anyone got a good idea there, given that I want them to meet the rafters at the same cleats? Besides, I need tie-in, particularly for the timber SW wall. I've already installed ceiling joists from the W wall of BR2 across to a large strutting/hanging beam that runs N-S in the middle of BR3. They're fixed with joist hangers as the beam is low to stay within chamfer limits at the outside walls.

  There are no bedrooms marked, so I dont know what youre talking about. Draw them on the plan. Making a separate ceiling joist plan, would be the best way to convey whats going on.   

> This puppy is DEFINITELY going in my CV. 
> Cheers,
> Grant

  Well if you put this together properly, then it would definitely be something to be proud of Grant.   

> Chipperchip,
> This is not a answer to any of the myriad of questions you ask. 
> In fact I'll be real surprised if:
> (a) anyone reads all that you have written, 
> (b) understands what you want, and 
> (c) bothers to take the time to write, what I suspect will amount to "Roofing 101", in reply.  
> Still, maybe someone with the expertise you seek is prepared to take the time.

  Thats a bit harsh. These forums are about asking questions of any building matter no matter how complex and time consuming they may be. If you cant offer assistance, then offer encouragement, or say nothing, but dont discourage people from asking questions.
I happen to have time on my hands, and we all enjoy sharing our knowledge and helping people out. I might get a greenie out of it.  :Wink:   

> One thing that does strike me though is, given you are asking a whole bunch of questions, and given you do get a response to them, wouldn't it be a just a bit cheeky to plonk it on your CV as your own work?? 
> Ian

  As I said, I taught myself how to pitch a roof, but I had help from people dating back to before the first pyramid was pitched. These include Pythagoras, and the people who have pitched the roofs that I have looked at. I didnt invent my methods, and Ill explain them in detail after Ive helped Grant out if you like. Its quite simple if you break it down to one word, and an understanding of basic formula extrapolation. 
If Grant can pitch this roof, and have an understanding of how it was done, so that he can do it again with completely different dimensions, all on his own, then he can proudly say that he built this roof all on his own. He doesnt have to credit his first grade teacher who taught him the basics about simple addition, and he doesnt have to credit me in his CV either.   

> You made mention of the fact that you did not undertake an apprenticeship, that becomes obvious with your sketch and also your notations for various theories.

  He comes across to me as a person who has a good understanding of a very complex matter, and he's asking the right questions. He has explained everything clearly and I understand everything that hes talking about.   

> Ok, I'll resist the feeling of being talked down to ;-)

  Dont let them worry you Grant. Its just the way the internet works.  

> First up, Ian, if you suspect a useful reply "will amount to "Roofing 101"" then I suggest you stick to making furniture and using your triton to rip 2mm slices off the bottom of doors. I hope it was a pretty door mate. Buy yourself a planer. I came here looking for help with a genuinely tricky roof, not abuse from a habitually condescending smart alec.

   :Minigun:    :2thumbsup:

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## pawnhead

> The roof layout is a result of the architect extending the octagonal room below straight up, and this is all on the inspected and planning-approved drawings. The roof we removed before extending up was simply an octagonal roof on the end of an E-W minor ridge - considerably simpler and something I've half built in the past from a friend's trade school notes (I simply didnt have time to devote to finishing it). 
> The ceiling height change isn't on the original approved drawings though, as the architect hadn't done a site visit and had missed the step in the existing lower ceiling that has now resulted in the step upstairs, and the beams and eaves.

  That gives me a better idea of what’s going on (sort of). So it’s an upper floor extension? Are the fascias going to be the same level all the way around? Are you marrying in to an existing fascia?   

> Sorry if I've left some stuff out - I was trying to keep clutter on that drawing to a complete minimum. That sketch is actually to scale (CAD output) that I drew up from site measurements - yes, the framing is already up. Attached is a similar sketch showing what the pitches should be. The highest is 27.2 degrees, and the lowest is 25.5. There will be no significant difference in eaves overhangs. I have another showing hip and valley runs. I also have a basic elevation I produced from an earlier proof-of-concept plan, but it would need to be reworked. Do you think it's worth re-doing? Perhaps some sections?

  Post it all up and I’ll have a look at it.   

> This roof WILL work, and it will go up substantially as shown - I'm just trying to get some idea on how to do it in less than two weeks

  Of course it will, and you should have no problems with the manpower you’ve got, depending on how big it is of course. There’s no dimensions that I can read.   

> Yeah, that's the way I felt about it at about revision 5 of my own drawings. This is rev 10 and I feel a whole lot better about it. The pitches work and I can see the wireframe in my head, but I still wish I had a 3D CAD package to actually build it in..

  I’m just trying to get the hang of Googles free Sketch Up CAD program. It takes me longer than pencil and paper, but with practice it would be a handy tool.  

> I usually resort to drawing joints out full scale (if possible) on a sheet of ply or a smooth concrete floor when I get stuck. I reckon if it were me building it, I'd be spending more time drawing than marking and cutting.

  That’s how my old man taught me originally. He was a cabinetmaker, turned carpenter after he migrated here. It’s not the easiest way though. You can get that little red roofing book that I’ve heard of, but it doesn’t give you any understanding, and I’m not sure if it covers bastard angles. Ditto for the roofing square method. 
The most accurate way is through trigonometry. With a $10 calculator and a little bit of knowledge, you can calculate anything that you want, with any combination of dimensions and angles, to an accuracy of however many decimal places that your calculator goes to.  

> Pawnhead : thanks for looking at this! No, the rafters are not exposed. It's all coupled, with a ceiling, and the eaves will be enclosed too (hangers and eaves joists).

  Yeh I realised that when you started talking about ceiling joists. I was part way through getting my head around it. Can you provide an accurately dimensioned floor plan, including the offsets of the supporting levels (timber/steel beams) in plan and elevation. I don't mean an elevation drawing, just the height differences will do if they are already set in place, and the offsets measured to the outside corner, either from the inside of the fascia, or the outside of the existing pitching point. 
I know that you've described them, but if you could include dimensions on that plan it would be much more understandable.  
Are the fascia boards going to be the same level all the way around? 
Is that CAD drawing accurate? Because the South East face of the octagon doesn't run at 45 degrees on that drawing.   
Here’s some pics of a job I did ages ago. I was foreman with four chippies under me, and all I’d pitched before that was a simple gabled roof, but it’s just a compilation of the same methods I used. It was during a long rainy spell so we cut all the rafters inside under the first floor slab, and I was a bit nervous that my calculations would be right. The boys did the straightforward stuff, and I tackled the (part octagon) bay window, and the lighthouse on top. It had exposed rafters and posts, with glazed sidelights and roof and it looked pretty sexy when it was done.

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## pawnhead

It’s a long time since I’ve pitched a roof so I’m a bit rusty. I won’t guarantee that I won’t make a mistake somewhere, but mistakes will generally stand out like dogs nuts. You can double check each trig calculation that you make, by attacking it from a different angle and you should come up with the same results.  
Firstly, if the fascias are all the same height, then forget about eaves, pitching points, offset heights, etc, for the moment, and concentrate on the height in the centre of the rafter/valley/hip at the top, at the very bottom end, just behind the fascia board.  
Then don’t think of an octagon, but think of a square, layed on top of a rectangle. Then to get your irregular octagon, work out these three angles: -  
Then you can work out the pitch of each with the following formula: -  
[tan roof pitch / (1 / cos angle ) ] atan = hip pitch  
Then work out the offset from the end of the rafter to the outside of your pitching point, and calculate the height difference using trig (I’m assuming you know how). Allow for the plumb depth of the rafter, less the birsmouth. This depth is the same plumb distance on your hips, but you have to bear in mind that the top corners of the hips must be planed down to a point in the middle, in line with the plane of the roof. You can leave the top square if drop the hip accordingly. It’s just another compound angle to work out. The face of the birdsmouth can also be cut to an internal point, if you want tight joinery. I’d only bother with that if they were exposed. 
Your rafters aren’t exposed, but if they were then you’d have to get your hips coming to a point in the centre (or pitch them to an octagonal block at the top).
Your cheek cuts are simply half the angle between hips, taken horizontally. I don’t bother working out the angle on the pitch. I simply lay down my saw on a 45 and cut to the long point with a plumb cut, then set my bevel to an angle, and start planing with the electric planer. Check the angle, square from the plumb cut, not parallel with the rafter, and check it with a straight edge, taking less off as you get closer to home. 
But since you’re rafters aren’t exposed, I’d do it differently, with a method that makes it easier to get it up there, not having to join pointy rafters together. I’d pitch three common rafters over the octagon first as shown here: -   
Work out the lengths using trig, and then pitch the two opposing rafters first. The third rafter butts into the side of the first two, so it has to be half their thickness shorter, measured horizontally from the plumb cut. The top corners of the rafters should line up with each other, and it should look like this in elevation: -    
Then get up on the ridge with a short straight edge a pencil and a chisel. chisel off the part of the abutting rafters to the centrepoint,then sight the straight edge from the centerpoint to the corner of the octagon (pitching point) and mark the top of the rafters with a hip centreline. Then drive a nail in the outside corner of the rafter at the hip centreline. Hook your tape on it and measure diagonally from this point to the pitching point intersection. Cut and plane the top of your hip rafter to the appropriate angle.  In the region of your birdsmouth, mark a plumb line and measure down the depth of rafter remaining above the birdsmouth. From this point mark a parallel line on the rafter. With your tape extended and locked, position it on a diagonal from the top centre, down to the parallel mark at the birdsmouth. Adjust its position until the length coincides with the line and the centrepoint at the top and mark it. You now have the position of your birdsmouth. Cut and install. 
In plan, after your hips are installed it should look like this: -   
At the top intersection you will find that the top of the hips are lower than the rafters at their long point, and they stick above them on their short point. Using a straight edge, or line of sight between adjacent rafters, plane the tops to a point. All of the roof planes should converge to the centre point now.  
Hook your tape on top of your rafter and measure perpendicular towards the hip. Mark 600mm on the top of your hip, then move down the rafter and mark 1200mm, etc. These are the long points for your creeper rafters, and after marking their positions on the pitching plate, you can use the diagonal measuring technique to cut all your creepers. They all step down in the same incremental lengths, and they should be the same lengths for both sides, except with opposite bevels on the top.  
Now you have the Eastern half of your octagon pitched. 
TBC

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## Ian Smith

Chipperchip, 
You're right, I should stay out of things I know nothing about, so I do apologise if I've pushed your buttons.
I still think you might hold the record for the biggest and most complex OP for a thread, but it looks like you've struck paydirt with Pawnhead - so good luck.  
Ian

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## ChipperChip

Wow, Pawnhead. A string of things come to mind! Many thanks again, and I'm in utter awe of that first roof of yours. I'm good with trig, but in fact I've cheated a bit with my calculations so far and have manged to get away without any trig so far. I've used pythagoras' of course (which is really just basic geometry). I've used ratios taken off the original roof, and dims off my CAD. 
I'll do some more drawings and come back later. Is there any easy way to post higher-resolution images than the 800x600?? I'll go digging thru the forums, it's got to be something people have asked before.   

> That gives me a better idea of what’s going on (sort of). So it’s an upper floor extension? Are the fascias going to be the same level all the way around? Are you marrying in to an existing fascia?

  Yes, yes and yes. Sorry again for missing stating those up front. My tired brain was forgetting you haven't been thru the same process I have  :Wink:    

> Is that CAD drawing accurate? Because the South East face of the octagon doesn't run at 45 degrees on that drawing.

  Yes it is pretty much perfect. And you're right, it's not at 45 degrees. It's about 40 & 50. So this isnt just a regular octagon, it's a slightly squashed one. Dont you love renovations. Actually, architecturally it has to be squashed to make the courtyard below work. 
I'll do a much more thorough plan view with the internal walls, remaining propping beams, dims and R.L.'s. I'll try to knock up a section, and a ceiling joist plan sounds like a very good idea. I just need more detail than I can squeeze into a 100k jpg  :Frown:  What I'll also try to do is something to demonstrate what I meant by treating those bastard hips as commons... 
Once again, huge amounts of thanks to you Pawnhead - I hope you drink beer mate  :Wink:  One of my side projects at the moment is building a microbrewery.

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## pawnhead

Ah, OK. I'll address your post later and explain trig a bit better if you want, but I've been pretty busy with other matters this morning, and I'll have to go out now so I'll post again tonight some time. 
I've got this much ready anyway: - 
Next, using trig, pitch as much as you can of the standard hip roof, from the existing roof traveling Southward.
If you’re not familiar with trig I can explain it to you. You obviously need to understand it well for most aspects of my methods, but there’s a handy calculator that you can use for a basic rectangular roof set out. One of the members here. Blocklayer, has the program on line on his website here.
Before you pitch the southernmost rafters, and the creeper rafters, put a temporary prop under the ridge so it’s dead level. Then run a stringline on top of the rafters, as illustrated here: -    
Anyone should feel free to ask questions if they are confused and interested, but I’ll deal with Grant first.

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## journeyman Mick

> .................Thats how my old man taught me originally. He was a cabinetmaker, turned carpenter after he migrated here. Its not the easiest way though. You can get that little red roofing book that Ive heard of, but it doesnt give you any understanding, and Im not sure if it covers bastard angles. Ditto for the roofing square method. 
> The most accurate way is through trigonometry. With a $10 calculator and a little bit of knowledge, you can calculate anything that you want, with any combination of dimensions and angles, to an accuracy of however many decimal places that your calculator goes to.............

  John,
I've used trig to work roofs and other angle stuff but it's generally ages between goes so I tend to forget how and need to ring an engineer maths geek mate for a refresher. I also tend not to trust myself to get it right 100% of the time, I know I'd stuff it up quite badly in maths at school on occcasions. I understand how it works, just not confident in my own abilities I guess.  :Blush7:   But yeah, if I had to do a big, complex job I'd sit down with my mate for a refresher and whip out the old HSC calculator. 
Mick

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## journeyman Mick

Just like John and Grant, I didn't do an apprenticeship. Learnt by watching and doing with a bit of reading thrown in. Would have done more reading, but there wasn't anything suitable. Never worked with anyone who pitched a roof so had to work it out myself. Used trig for the valley rafter on this job and managed to cut it about 100mm short  :Mad:   (although looking back, perhaps it was the old tape measure trick) 
Became really good friends with the owners of this place, there was only one page of plans, no details so we had a breakfast meeting once a week (hot chocolate, croissants, freshly laid eggs etc) to work out all the details for the week to come. 
The building is "L" shaped, with a 3M wide verandah all around + 1M overhang. No internal doors, they all open onto the verandah. No privacy issues as it's on over 100 acres and the nearest neighbours are quite a distance. First pic is looking from the inside corner of the "L" out towards one end (ends are all hips)
pic 2 is looking down the valley framing
pic 3 is a general internal shot, before the internal walls went up or the stone cladding went onto the steel frames.
pic 4 is looking up one of the ridge posts (300 x 300 red stringy, cut on site) showing the hip rafter intersections. Tight enough that you couldn't get a bit of ciggy paper in there. The rafters line up with the geometric centre of the post, but because it was milled with a hagen saw they're a bit wonky.
Pic 5 is a view along the finished verandah, steelwork is clad with locally quarried stone. Doors and windows made on site in Jarrah, cladding under windows in brushbox, louvres next to doors (barely visible) in WRC. 
Mick

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## bricks

This thread made me seriously think about my own ability to build and entire house by myself, trussed roof = no worries, this stuff= my house comes tumbling down, Good on you guys for having a go but im lost as of the first post.

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## echnidna

Its not that hard Bricks when you think about it,
You just got to get the ridges in place first then the hips and rafters fall into place from there on. 
Maths is ok but drawing it out full scale on the floor is a good double check.

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## AndrewPatrol

One of the most interesting threads for a long time. Like was said before, no such thing as a dumb question, and if you dont challenge yourself then life gets a bit boring. Good on ya Chipperchip and best of luck. One thing I thought of ( may be a waste of time though ???) is - have you considering making a simple model? No need to reply ,you probably havnt got time. Just an idea.

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## boban

Impressive fellas

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## ChipperChip

Nearly finished the drawings! That was harder than I expected. Sorry about the delay Pawnhead, Mick and others. 
OK, this should be a lot more info, although I've not flooded it with dims. I hope I got the balance between clutter and info right. It's worth noting that I'm not completely confident about the dims in the area of the NE and N walls of the octagonal roof, but it's kind of a moot point. We're talking principles here not five decimal places, and I know it's close to right. I'll be re-measuring everything before I actually put this up anyway. 
There are a few changes to the look of this where I've cleaned up some approximations that didnt matter so much before. A-A' is still the line of the original hip end, and B-B' is the line of the section I'm still preparing, which I will try to get up in the next half hour. The ones I'm uploading now are: 
1) A dimensioned plan showing all loadbearing elements in the roof except two hanging beams BR2 and void areas). Red beams are propping beams for the roof structure, and blue beams are those that take the perimeter roof load where it's not being taken by the wall. Note that the red beams are offset from the centre because they have to land above joists below, and I'll be honest I had so much on my plate back then I failed to think the joist placement through properly. 
2) A plan showing the area over which the ceiling height is 190 higher than in the rest of the upper storey. The RL's for the floor show where the step is (E-W on the landing, at the SW corner of the stair void). 
3) An elevation of the roofline. This is worth seeing to understand just how shallow the pitch of the long broken hip is. It calculates out to just over 9 degrees. 
4) A plan view with a 'normal' hip-end superimposed over the octagonal roof to try to convey what I meant about treating the broken hip as if it was a ridge, and the two bastard hips as if they were common rafters. Of course, once this is up I wouldn't be looking at it like a hip end, but I hope you can see what I mean from... 
5) A closeup of most of the timbers at the peak that would result from doing this. I didn't do the other rafters coz frankly it's midnight. 
and lastly
6) A plan view of the proposed ceiling joist layout. 
The tricky part about getting the octagonal section up correctly in this way is making sure the three bastard hips are cut right and that the west end of the broken hip is propped at the right height. That's why my main original question was about what to do around the (very short!) minor ridge. I guess I could just put a block in where the broken hip will eventually go just to let me get it all to the correct height to measure the broken hip and to stringline for the minor ridge. 
Oh, and when I said I hadnt used any trig...  obviously I did to get my expected pitches of the faces of the octagonal area. And I just extended the spreadsheet to give me the pitches of the bastard and broken hips. 
I hope all that makes sense. I'm going to finish this last drawing then get some Z's and will check here in the morning before work (eek... in 6 1/2 hours) to see if there's anything anyone needs me to add... that's if you're all insomniacs.

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## ChipperChip

Oops, only lets me put 5 images up for some reason... 
Here's the ceiling joist layout I'm proposing. This is just an indication of course - but it gives the idea of directions and so on. I'm thinking I'd tripl-grip all the angled joins.

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## ChipperChip

The section isnt going to happen tonight. My brain just switched off and I can't get it started again. Sorry folks, but the relevant bit is in there (crosshatched part of the siren). I couldn hear a thing!

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## pawnhead

> Yes it is pretty much perfect. And you're right, it's not at 45 degrees. It's about 40 & 50. So this isnt just a regular octagon, it's a slightly squashed one. Dont you love renovations. Actually, architecturally it has to be squashed to make the courtyard below work.

  That’s not a problem. You just have to check all your dimensions on site.   

> I'll do a much more thorough plan view with the internal walls, remaining propping beams, dims and R.L.'s. I'll try to knock up a section, and a ceiling joist plan sounds like a very good idea. I just need more detail than I can squeeze into a 100k jpg  What I'll also try to do is something to demonstrate what I meant by treating those bastard hips as commons...

  Don’t worry about any of that.   

> Once again, huge amounts of thanks to you Pawnhead - I hope you drink beer mate  One of my side projects at the moment is building a microbrewery.

  I don’t mind a beer occasionally, but I don’t expect a shout unless we bump into each other in a pub. Just buy yourself a foily.  

> OK, this should be a lot more info, although I've not flooded it with dims. I hope I got the balance between clutter and info right. It's worth noting that I'm not completely confident about the dims in the area of the NE and N walls of the octagonal roof, but it's kind of a moot point. We're talking principles here not five decimal places, and I know it's close to right. I'll be re-measuring everything before I actually put this up anyway.

  All good. Those drawings look good (except for a couple). The offsets are critical, as are all the dimensions verified on site. You’ll have to measure/double check all of the offsets before you do any birdsmouth calculations. Check the RLs of all your pitching plates.    

> 4) A plan view with a 'normal' hip-end superimposed over the octagonal roof to try to convey what I meant about treating the broken hip as if it was a ridge, and the two bastard hips as if they were common rafters. Of course, once this is up I wouldn't be looking at it like a hip end, but I hope you can see what I mean from...  
> 5) A closeup of most of the timbers at the peak that would result from doing this. I didn't do the other rafters coz frankly it's midnight.

  Forget about that. Throw all that junk away. It's not ridgey-didge, calling it a ridge. 
Get hip. It’s a _flying_ (broken) *hip*!   

> The tricky part about getting the octagonal section up correctly in this way is making sure the three bastard hips are cut right and that the west end of the broken hip is propped at the right height.

  Of course. Verify dimensions before we start the calculations. Locating their position on site isn’t a problem. Plumb bob, tape measure, water level, Isaac Newton.   

> I hope all that makes sense. I'm going to finish this last drawing then get some Z's and will check here in the morning before work (eek... in 6 1/2 hours) to see if there's anything anyone needs me to add... that's if you're all insomniacs.

  I keep very irregular hours.
For the past three years I’ve been a full time carer for my aged mother who suffers from bipolar disorder amongst other medical ailments. It gets very demanding mentally at times, but it’s not that big a workload, so I’m happy that I have time to spend renovating this house, and surfing the web. Life is pretty good at the moment, and I always look at the bright side. 
I’ll explain how I’d pitch this *hip*, and deal with _SohCahToa_ when you’ve checked your dimensions.  

> The section isnt going to happen tonight. My brain just switched off and I can't get it started again. Sorry folks, but the relevant bit is in there (crosshatched part of the siren). I couldn hear a thing!

  Don't worry about it. 
Just fill in that plan.

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## ChipperChip

> The section isnt going to happen tonight. My brain just switched off and I can't get it started again. Sorry folks, but the relevant bit is in there (crosshatched part of the siren). I couldn hear a thing!

  Where the HELL did THAT come from....  Crosshatched part of the siren?? Couldn't hear a thing?? OK, my brain really was fried... 
Feeling better this morning. 
Thanks Pawnhead, will get all that today. Dont fret about me calling that broken hip a ridge  :Biggrin:  I KNOW it's a broken hip. I just meant that in terms of the construction of that joint in the octagonal section, the layout in plan looks a lot like a (slightly uneven) hip end IF the broken hip had been a ridge. If my dims are right and the spreadsheet gives me a length and angle, I feel I can trust it and build it as such. At this point I feel more comfortable with that way of achieving the octagonal area but I'm gonna get your measurements today and see how your plan works out. But I'll be honest I dont really think I should have rafters coming together there, from a load bearing point of view mainly. Surely it should be the (larger) hip rafters that are joining up? Rafters there also make it tighter to work in, but that's obviously less of a consideration. Did my enlarged view of how I thought that joint might work make sense? 
You've already made me see the easy way to pitch the main roof's broken hip so I can stringline the minor ridge, for a start  :Smilie:  Still struggling with what to do around the east end of the minor ridge but perhaps that will have to go by spreadsheet and faith too. But at least I now understand exactly which dims are critical. 
We're getting there. I'm due on site twenty five minutes ago tho and typing more isn't getting me THERE. Glad the boys have plenty to do. Later.

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## pawnhead

> If my dims are right and the spreadsheet gives me a length and angle, I feel I can trust it and build it as such. At this point I feel more comfortable with that way of achieving the octagonal area but I'm gonna get your measurements today and see how your plan works out.

  Fair enough. If you can plug your dimensions into a program and come up with the measurements then you dont have to worry about trig, but Ill keep going with my explanations for the benefit of anyone else who may be interested, and when Im done I might give a run down on trig if anyones interested. Theres explanations on the web, but I think I can explain it a bit simpler, and also explain how to get compound angles for hips and valleys.  

> But I'll be honest I dont really think I should have rafters coming together there, from a load bearing point of view mainly. Surely it should be the (larger) hip rafters that are joining up? Rafters there also make it tighter to work in, but that's obviously less of a consideration. Did my enlarged view of how I thought that joint might work make sense?

  That looks alright structurally. If your program can spit out all the dimensions and angles for that, then I cant see anything wrong with it. I take it that you have deeper hips than your rafters. It was common in the old days to use 6 X 1 for hips and valleys, and of course you can still do it that way, but I just use 4X2 for everything. As Ive said you could cut them all to a point, but thats the most time consuming way.  

> You've already made me see the easy way to pitch the main roof's broken hip so I can stringline the minor ridge, for a start  Still struggling with what to do around the east end of the minor ridge but perhaps that will have to go by spreadsheet and faith too. But at least I now understand exactly which dims are critical. 
> We're getting there. I'm due on site twenty five minutes ago tho and typing more isn't getting me THERE. Glad the boys have plenty to do. Later.

  Ive explained a bit more of my pitching process, but I havent got up to that Eastern point yet. From what I have done, you can see that its easy to set up stringlines to locate that point. As Ive said, you could also sit down with a calc, and cut everything on the ground, and just put it together like a mechano set: - 
Ive amended the last drawing to explain a bit better how to set out the broken ridge. 
Set up stringlines at the ceiling level in line with the two walls as shown. If theres hangers or beams in the way, then off set the lines up, down, left or right, to wherever you can get a clear run. If your walls are a bit out of parallel its not a big deal. You just have to mark the centre on the ceiling joists, and pull a line under where the ridge is, and transfer it up to the rafters with a plumb bob or spirit level. Then you can run a line for the top of the ridge.   
Next, nail a temporary prop to the ceiling, plumb it up, and brace it back. Hold your tape against the first creeper rafter on the South Western corner, and by eye, line it up with the Eastern roof plane of the main roof. Cut a piece of ridge 600mm longer than your measurement, then install the broken ridge, butted against the last creeper rafter, and nailed to the prop as shown here.   
Next, run a stringline from the top of the main ridge, somewhere close to the southern end, down to the bottom of the last main roof rafter on the Eastern side. 
Run another stringline from back on the Eastern roof somewhere (the position isnt crucial), intersecting the first stringline, and extending past over the broken ridge stringline.
Now you have two fixed stringlines, and youre holding a third one over your ridge. Adjust the position until it just touches the other two stringlines, and mark the ridge below.     
Note in that second detail, the height of the South Western hip in relation to the height of the top of the main ridge. I'm working to centre lines all the time, and the central point at the top of that hip is the intersection of the three planes. It's outside edges are high and must be planed down, or it must be set at a specific lower height that can be calculated. That's why the creeper rafter is shown installed lower than the top edge of the hip. Planing the corners down gives better support for the roof battens. I've shown all the ridges installed low so they don't have to be planed down. 
Drive in a nail in the centre of the broken ridge, on your pencil mark. Let it stick up so it just touches the stringline above. The top of this nail represents the intersection point of three roof planes. Drive a nail on an angle into the long point of the hip at the top. Hook your tape on this nail and extend it down to the nail in the broken hip. Sight the measurement plumb down to the Northern face of the broken ridge. Cut and install your broken hip. 
From the drawing it looks like your valley rafter has no eaves overhang at the bottom. You can use trig to calculate its length, or you can measure it. I havent mentioned this yet, but check that the bow is up on all your timbers before you cut them. Cut and install your valley rafter, and it should look like this at the top: -   
Bear in mind, that whilst your hips are high at the edges, your valley rafter will be low. After measuring your cripple rafters (the ones that go from the valley to the hip), make sure that when you install them, you leave them down from the top edge of the hips, and up from the top edge of your valley. The top faces are supposed to line up with the centrelines. You can calculate the exact distance if youre fussy, or you can just mark it on a scrap and measure it. 
Now you should have a roof that looks something like this: -    
BTW None of this is to scale. I'm just using a photo program with no scale capabilities and I'm just guessing the joist spacings. 
To locate that point, you can use trig, but its just as easy to install your fascia board along the Southern end of the main roof first. Make it slightly longer than you need it on the Eastern side. If there is no rafter near the end, then make sure its straight, and brace it if you have to. Trim your South Western octagon hip rafter to length, if you havent already done that prior to installation. Run a stringline from its end, over to the fascia youve installed and check that its parallel to the pitching plate. Mark the back of the fascia, and cut it on an angle which is half of the overall angle between the two walls. Measure down the edge of the fascia and mark the top of the roof line. This is the centre-point for your next valley rafter.    
Anyway. It's lunchtime and I'm going out back to lay some floor boards.  :2thumbsup:

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## pawnhead

> pic 4 is looking up one of the ridge posts (300 x 300 red stringy, cut on site) showing the hip rafter intersections. Tight enough that you couldn't get a bit of ciggy paper in there. The rafters line up with the geometric centre of the post, but because it was milled with a hagen saw they're a bit wonky.

  That's where those fish plates come in handy eh? That's a nice looking house. You did a great job on that roof.
BTW what's a hagen saw? 
I've never installed posts that big although I pitched a roof on a poll house built on exposed pine poles. I was foreman carpenter, but the builder already had the poles installed when I arrived on site. I think they were just concreted in but I can't remember.
I'll try to dig up the pics.

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## journeyman Mick

John,
a hagen saw is basically a carriage, usually a pair of holden wheels on an axle with a trailer jockey wheel to steady it. See sawing on top of this is a long pole, on the short end, just behind the carriage sits a motor, often a VW. The other end of the pole is a lot longer and carries a humungous saw blade, driven by a belt from the motor. There's usually a water reservoir and a pump top deliver a spray to the blade for cooling and lubrication. If it's really fancy there will be a few hessian bags hanging off the carriage to slow down any chunks that get thrown back at the operator.  
Operator makes a few crayon marks at either end of the log and just eyeballs his cut from one end to the other. Suprisingly quick and accurate with the right operator. Bloody frightening contraption though. :Shock:   I posted a pic of one in a quiz thread here a while back and just did a search for it, but I've got a feeling it's old enough that it was archived and doesn't show up in a search. 
Mick

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## pawnhead

Wow, that sounds like my kind of saw. 
A big version of the table saws I used to set up on site from a slab of pineboard. No guard or anything.  :Biggrin:

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## pawnhead

Here's the job I was looking for. Exposed timber poles inside and out, supporting big exposed trusses that I built up in place off a scaffold. One triangular truss, and three parallel chord trusses, then pitched the roof on top of it. sexiest house I've built, with a wet edge pool looking down on Whale beach on Sydney's North Shore, and it was just their weekender. (why doesn't some of their bloody money rub off on me  :Mad:  ) 
I had a three story fall on that job as well. Landed on a pile of mud luckily. Got up, scraped the mud off, and went back to work. My back got worse over the next few years, until I was laid up in bed for a year. Had an operation and it's alright now, but still gets a little sore sometimes.
My own stupid fault of course. Not to worry.

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## journeyman Mick

John,
nice  :2thumbsup:  
bugger about the fall. Of course with all the safety regs now that stuff doesn't happen anymore, does it.  :Rolleyes:   
Mick

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## journeyman Mick

John,
go here and see my post, no. 308 for a couple of pics of a hagen saw. Actually the bloke cutting the posts for that house I did. 
Mick

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## ChipperChip

Very quick post. Been up all night dealing with a personal situation when I'd intended to be drawing, then catching up with drawing. Working after no sleep... great. Thank god I'm not using power tools. 
Pawnhead, have printed your long post and images with it. Thanks very much, looks like it's exactly what I need. Will post new sketches soon but I think I've got it sussed now! Of course that might feel different tonight  :Wink:  
Awesome roof and saw pics too, guys  :Smilie:  I'll add this little puppy to the thread when it's done, but it's not anywhere near as impressive visually. Just a little roof on a very ordinary building - not those gorgeous places you've been working on <snif> 
Grant

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## zenwood

Some interesting geometry happening here.  Just wanted to see if I could quickly draw the overall shape in sketchup.  Answer was yep.

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## pawnhead

> This thread made me seriously think about my own ability to build and entire house by myself, trussed roof = no worries, this stuff= my house comes tumbling down, Good on you guys for having a go but im lost as of the first post.

  I’m sure you could do it if you learnt a bit of trig. It’s a bit like installing a valley _flashing_ with the appropriate angles cut.  :Wink:   
Just read my instructions carefully, and I’m happy to explain anything that you don’t understand.  :Smilie:   

> John,
> go here and see my post, no. 308 for a couple of pics of a hagen saw. Actually the bloke cutting the posts for that house I did. 
> Mick

  Wow, that looks *awesome*. 
I wouldn’t mind one of those, and a hundred acres somewhere with ocean views.   :2thumbsup:   

> Very quick post. Been up all night dealing with a personal situation when I'd intended to be drawing, then catching up with drawing. Working after no sleep... great. Thank god I'm not using power tools.

  People don’t appreciate the time that’s spent off-site at night, doing calculations to ensure that there are no mistakes made on-site.  :Mad:  
You live and breathe the job sometimes.  

> Pawnhead, have printed your long post and images with it. Thanks very much, looks like it's exactly what I need. Will post new sketches soon but I think I've got it sussed now! Of course that might feel different tonight

  I’ll finish my set out tutorial soon, but I’m very busy with another important matter at the moment.
I take it that you’re OK with the calculations since you haven’t posted any site dimensions as yet. 
If you want me to check anything then just ask.   

> Awesome roof and saw pics too, guys  I'll add this little puppy to the thread when it's done, but it's not anywhere near as impressive visually. Just a little roof on a very ordinary building - not those gorgeous places you've been working on  
> < sniff >
> Grant
> < /sniff >

  I’ll be expecting some pics.  :Smilie:  
BTW. If you want to display anything in these parentheses <  > then you have to leave a space before your wording, or it’s picked up as HTML code and it’s invisible in the post. It came up when I hit "Quote".  :Wink:   
A few points to mention. 
Before you install your cripple rafters and jack rafters, brace up your valley rafter so that it’s straight. You could use a stringline, but your eye should be good enough. 
At all stages of construction, keep an eye on all of your roof planes. By sighting along the top of the roof, you should be able to pick up any discrepancies that are more than + / - 5mm. It may look a bit wonky because some of your members may have a larger upward bow than others. They will be straightened out when you install your purlins (if there are any), but any glaring errors should stick out like dogs nuts at this stage. If there are any, then obviously you have to backtrack and find out where they are before progressing any further. 
Any noticeable bows that won't be straightened out with a purlin should be planed out.  

> Some interesting geometry happening here.  Just wanted to see if I could quickly draw the overall shape in sketchup.  Answer was yep.

  That’s brilliant zenwood, although you have the same eaves dimensions all around, and a symetrical octagon, whereas Grant doesn't. As I’ve said, I’m just trying to get the hang of Sketchup, but I’m very slow. It would certainly be handy to have all these sketches of mine to scale, and being able to rotate them in 3D would be a bonus. 
In those perspectives you can see what Grant was talking about with the broken 'bastard' *hip*. It has a much shallower pitch than all the others. 
To do the job so it's technically perfect and symmetrical, you'd have to pitch three different hips there, to imaginary points corresponding to the octagon corners.
Of course this would involve a lot more work, and the valley would have two doglegs in it.

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## pawnhead

Carrying on from where I left off: - 
Once you’ve located the bottom of the Southern valley, it’s a simple matter of running two stringlines to locate the top: -   
Then using the same methods as described previously, you can measure your last valley, cut and install. With inside angles, I usually cut a beak in the bottom of my valley rafters to support the fascia joint, but you could cut it short and put a cleat on each side to support each adjoining fascia. Ditto, with outside angles, I usually cut my hips to a point. 
Then cut and install your broken bastard *hip*.
Then determine the positioning of your rafters, and cut the 600mm overhang on the broken ridge, so that it butts into the nearest rafter.
The intersection should look like this in plan: -     
And the completed roof framing should look something like this.    
Then after you've installed all of your purlins (do you need advice?), valley boards, fascias, anti-ponding boards (if you can be bothered with them), and eaves linings, get a piece of builders plastic about half a metre square, nail it to a stick, draw a picture of a pawn on it  :2thumbsup:  (j/k you don't have to do that  :Wink: ) , and nail it to the highest point of the roof.      :Brava:  ..................................................  .................  :Aussie3:   
It's a signal to the builder that he’s not allowed on site unless he has a slab of beer under his arm.   :Beer:   ..................................................  .......  :Bbq2:  
Then take some pics,   :Photo2:  and post them up.

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## ChipperChip

I wrote up a nice long reply to this last night, multiquoted and all. Then I shut the machine down without clicking 'post'....  ARGH! 
We have the main roof complete on the W side, all the SW jacks, the octagonal SE half and most of its jacks, and have the minor ridge in place with all the strings ready to do the W crippled hip. The double-birdsmouthing over both steel and top plate has been... entertaining shall we say. As has the fact that I made a glaring mistake in my reasoning. 
A 190 wall height increase results in a 400 eaves width CHANGE. This means that the overhang around the octagonal area is 475 (400 plus styrene) versus just 75 for styrene only in the areas without eaves. Stupid stupid simple reasoning mistakes like that really bug me, and I would have caught it if I'd prepared the section I was going to do but eventually decided against on the grounds that it would take too long and that I had it in my head already. HA! 
Thankfully it doesnt change anything we've already built except the overhangs on the bastard hips in the octagonal area. They can be extended easily because the eaves are closed. Took about a dozen photos today and will take more when we finish tomorrow. 
We will finish tomorrow because I'm bribing the boys with steak, snags, coleslaw and beer. No finish, no eat. Does that make me a bastard?  :Smilie:

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## AndrewPatrol

Chipper, 
A picture is a thousand words, post em up. :Wink:   
Interested

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## pawnhead

> Thankfully it doesnt change anything we've already built except the overhangs on the bastard hips in the octagonal area. They can be extended easily because the eaves are closed.

   Just extend them with a cleat on each side. It will look like it was intentionally done to give extra support to the fascia.
I never make mistykes. All my projekts are perfikt, except for that time I read the plans upside-down. But the best builders are the ones who know how to fix up stuff ups, so I talked them into making a novelty of it and everyone was happy.  :Wink:   

> We will finish tomorrow because I'm bribing the boys with steak, snags, coleslaw and beer. No finish, no eat. Does that make me a bastard?

  Not at all. Just look after the boys, and they'll look after you. 
Here's a few more shots whilst we're waiting : -  
Me on a roof, about twenty years ago    
A very wide dutch gable that had to be supported by diagonal props back to the house after the blue board was installed. I built the scaffold out of hardwood. (That's me in that first shot, with my 6 1/4" Makita in hand)    
A cedar glass pyramid at Double Pay (Double Bay)   
That's me in the foreground, and you can see the flag on the ridge, and the obligatory flanny shirt.   
This one at Harboard was trussed with a bit of stick work on the tricky bits.  (That's me on the right, and my brother on the left. I taught him the trade, partnered up with him, and we had up to four carpenters working for us at various stages of our contract carpentry business. You can see that we both like our K-mart flannys)    
Here's an unusual one.

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## ex-chippie

Hi Chipperhead,  Pawnhead is definetly putting you in the right direction. As i have done some 17 years of architectual conventional (stick) framing, my advice is to keep all hips and valleys running at half the angle of the wallplates that they are coming off. Who ever drew your architectual drawings has given you a bum steer! They are incorrect! A great book that will help you is the "Hancocks roofing manual", you should be able to purchase it from any (construction) tafe college bookshop. It will give you Rafter, Hip and valley lengths, as well as ridge heigths. A roof like this is impossible to explaine over a screen but Pawnhead sounds like he's your best bet!       
              Best of luck, Jason. :2thumbsup:

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## ChipperChip

> Hi Chipperhead,  Pawnhead is definetly putting you in the right direction. As i have done some 17 years of architectual conventional (stick) framing, my advice is to keep all hips and valleys running at half the angle of the wallplates that they are coming off. Who ever drew your architectual drawings has given you a bum steer! They are incorrect!

  Actually, I did the drawings myself. And they're not incorrect. If anything they're astonishingly accurate even if I do say so myself. In the end, I am sure I could have gotten away without them, and just used roof framing tables to pick up my plumb cut angles etc, but the drawings did help me get my head around how to set the roof out. If I HAD simply halved the angles of all my wall plates the roof wouldnt have worked. I would have had hip rafters that didn't meet. Pawnhead has definitely explained how to project the various roof planes around the place, and made it clear how well that technique works. I DID make a small mistake at the interconnection of the western broken hip and the valley, but nothing a bit of planing can't fix. I'm glad it's a tiled roof  :Blush7:    

> A great book that will help you is the "Hancocks roofing manual", you should be able to purchase it from any (construction) tafe college bookshop. It will give you Rafter, Hip and valley lengths, as well as ridge heigths. A roof like this is impossible to explaine over a screen but Pawnhead sounds like he's your best bet!

  I actually have a really neat basic roof framing book that has all that as well. I can't remember the name of it but it is a great 'join the dots' guide - to a basic hip ended roof for an L shaped building with different roof widths. Nothing this complicated. I've done all the calculations myself on this one, using a spreadsheet and some basic use of pythagoras and a little trig. It's all worked out very neatly in the end. The last two beams to put in were the eastern broken hip and its associated valley. They measured out to 15mm off what my drawings had estimated them to be. I reckon that's pretty good going. What has been a little disturbing is the depth of some of the birdsmouths, but I'll explain that in a later posting. 
Anyway, all the structural elements in the roof are in. I just have about 15 rafters to go, all creepers and jacks. Monday. Photos are coming  :Smilie:

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## Carpenter

Cooee fella's, daunting project, but like all things once you put your mind to it the only thing you cant do is wipe your bum with your elbow! All this talk of trig, I had to let you know about these calculators. I've had the same problem as others in that I forget all the trig stuff because I dont use it enough. This was really giving me the s&#37;$ts, so I ordered one of these;http://www.jobbercalculator.com/tutorial.htm
No longer will you ever suffer bewilderment from trig, this thing is worth its weight in gold.

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## pawnhead

> Cooee fella's, daunting project, but like all things once you put your mind to it the only thing you cant do is wipe your bum with your elbow! All this talk of trig, I had to let you know about these calculators. I've had the same problem as others in that I forget all the trig stuff because I dont use it enough. This was really giving me the s%$ts, so I ordered one of these;http://www.jobbercalculator.com/tutorial.htm
> No longer will you ever suffer bewilderment from trig, this thing is worth its weight in gold.

  35mb  :Eek:  
Does it give you a complete history of trig dating back to the pyramids or something? 
I could explain it simply in a reasonable sized post. It's not that hard, but of course you need some intelligence and a bit of practice.

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## Carpenter

> 35mb  
> Does it give you a complete history of trig dating back to the pyramids or something? 
> I could explain it simply in a reasonable sized post. It's not that hard, but of course you need some intelligence and a bit of practice.

  For the mathematically challenged :Shock:  , its fast, accurate, eliminates human error & most of all it saves precious onsite time. If you can do all that without one (as some people can) I'm jealous.

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## pawnhead

> For the mathematically challenged , its fast, accurate, eliminates human error & most of all it saves precious onsite time. If you can do all that without one (as some people can) I'm jealous.

  Oh, it's a running program is it?
That would save some time if you could just plug in your dimensions and come up with all your lengths and angles. And certainly it would eliminate a lot of potential for mistakes.  
I thought it was just lessons on trig.

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## Carpenter

Its a construction calculator, but I sent you the link for the tutorial..sorry about the confusion.

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## ChipperChip

> Its a construction calculator...

  That's freaky. The irish carpenter I have (had) working for me mentioned these things. I'd never heard of them, and now two days later someone mentions them here too! Dont know where he'd seen them because all he's done before this has been fixing (or, in Ireland/UK, second fixing). He must have seen them in use in Ireland I suppose. I dont think I'd pay for the fancy 10-15 buttons, given that I could never work in imperial. 
And yes, I say 'had' because he's decided to go travelling when I need him for another two weeks or so, and one of the apprentices has trade school all next week. Does anyone know a chip in Melbourne who wants a week or two's work?  :Smilie:

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## Carpenter

> I dont think I'd pay for the fancy 10-15 buttons, given that I could never work in imperial.

  Take a closer look there Chipper, this is a fully functioning metric calculator as well as imperial. So yes, it also can convert between the two. http://www.jobbercalculator.com/metric_conversion.htm

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## ChipperChip

I realise that. I'm not really interested in working in imperial at all, not even for conversions. For the VERY rare time I need to do that, I'm happy to do it long-hand. I'd rather not have to pay the extra as there are other similar devices that are cheaper. 
But I can see that it's potentially a very useful piece of kit, if I did more roofs. Give me a $5 trig calculator and I'll be happy. Actually, a free software one on my iPaq will do  :Smilie:   Between that and my cad package at home I'm sorted for pretty much anything. 
ps all, pics of finished roof by the end of the week. It has been a.... challenge  :Smilie:

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## pawnhead

Yeh, that just looks like a normal calculator to me, Carpenter. Chipper's right. $5 should do it, or $0 on the web.
I thought you were talking about a 3D cad program.

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## ChipperChip

And even more powerful for $0 on the web  :Smilie:  
Good for ordering concrete from very old concrete companies. 
Even useful for the things you never knew you wanted to know, like how long it takes for sunlight to reach the earth.

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## pawnhead

Wow that's pretty cool. I didn't know you could do that.  Cheers  :2thumbsup:

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## ChipperChip

:Smilie:  
And that's just BEGINNING to scratch the surface...

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## pawnhead

Yes I realise that there's lots of things you can do with Google.
On the OCAU website, there's a thread that mentions a way that you can use Google to search for web cams. You can tap in to peoples security cameras and operate them remotely. You can spy on people who are supposed to be working, or who believe that they have privacy. 
I can't find the thread at the moment, but I believe that there's nothing illegal about it since the people concerned haven't looked into installing security blockers or encryption, and are thus offering the information on the web.  Cheers  :Shock:

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