# Forum Home Renovation Structural Renovation  Changing from tile roof to colorbond

## barney118

This one is a theory question, If I were to change my roof from tiles to colorbond what do I need to do? 
Is it as simple as removing the tiles and placing new battens and screw sheets down if it is a conventionally pitched roof. 
Or is it different if I have truss roof? 
I asked this to my TAFE teacher (carpentry) and I had a response that a conventional roof doesn't need any bracing, but when I put up my trusses there was a bracing plan. I am thinking that the weight of the tiles plays a role compared to the lightweight of the steel. 
mmmmmm?

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## Belair_Boy

> I am thinking that the weight of the tiles plays a role compared to the lightweight of the steel.

  I agree.  The weight of the tiles is significant and the roof structure needs to be designed with sufficient strength to support the load.
With a metal roof, uplift caused by the wind is a bigger factor and the roof structure needs to be tied down appropriately. 
In designing my roof structure (trusses) I allowed for the weight of tiles and the uplift of steel so I have the option of either without any structural design changes.
Time will tell which method I end up using. :Smilie:

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## Bloss

> This one is a theory question, If I were to change my roof from tiles to colorbond what do I need to do? 
> Is it as simple as removing the tiles and placing new battens and screw sheets down if it is a conventionally pitched roof. 
> Or is it different if I have truss roof? 
> I asked this to my TAFE teacher (carpentry) and I had a response that a conventional roof doesn't need any bracing, but when I put up my trusses there was a bracing plan. I am thinking that the weight of the tiles plays a role compared to the lightweight of the steel. 
> mmmmmm?

  "A conventional roof doesn't need any bracing"  mmmmmm to that one. ALL roofs need bracing - it's simply that different designs for different loads might use different bracing. New concrete tiles on a roof will be 40 tonnes and more - so significant downforces will be the result relative to a steel roof. That means the designs will be different, but as belairboy says it is not too hard to design a roof which will carry either - but there will be additional cost with the tiled roof being dearer.  But in most cases you can replace tiles with colorbond - again as belairboy points out so long as you ensure increased tie-down is done. Depending where you are you might need building approval (not usually needed when like for like replacement is done).

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## barney118

Bloss, 
I should rephrase a conventional roof design is braced by the way it is constructed. So if you change from a tile to steel then would you need more tie down in the house? Given 40T of concrete vs 3 T of steel. 
Is there a general rule? i.e use triple grips on all rafters to top plate, use speedbrace across entire roof. Consider having to tie down through wall to footings etc.

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## Bloss

> Bloss, 
> I should rephrase a conventional roof design is braced by the way it is constructed.

  . . . using bracing, the same statement applies to trussed roofs too. So for example both will use speedbrace and equivalent (although older roofs will have timber bracing under the rafters). The issue is braced against what design loads - and that not to do with whether it is a trussed or cut-in roof. 
There is no 'general rule' - nowadays I'd get it plugged it into a package and see what was needed - or get an engineer to do it. As I said in most places so far as I am aware you can't replace a tile with tin or vice versa without approval and they will require technical review of the roof frame specs - and perhaps walls too although unlikely. 
But as you say I would be making sure the rafters are well-tied to the top plates so triple grips all round (I am assuming it's not cyclone area) and speedbrace according to spec - makes sure it is taken down over and under the plates as per destructions and use the correct type and number of fixings (which you no doubt know to do anyway).

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## PhilT2

> Bloss, 
> I should rephrase a conventional roof design is braced by the way it is constructed. So if you change from a tile to steel then would you need more tie down in the house? Given 40T of concrete vs 3 T of steel. 
> Is there a general rule? i.e use triple grips on all rafters to top plate, use speedbrace across entire roof. Consider having to tie down through wall to footings etc.

  Not my area of expertise but 40 tonne? I'm getting up there to check those trusses in the morning.

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## intertd6

Most 180 to 200 m2 cottages have about 12 tonnes of roof tiles which is carried to the site on a rigid bodied truck, a conventional hip roof used to not require any other form of bracing as the hips were a sufficient form of bracing. This discussion has been talked about before & with modern designed trusses for tile roofs the trusses will not meet the uplift design criteria let alone the truss tiedown, could be different for an older truss design though, where the designs have not been designed to the bare limit.
regards inter

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## sundancewfs

When we swapped ours out for colorbond the building inspector wanted us to make sure the tie-down on the framing met the applicable specs. other than that it wasn't a problem. Take the opportunity to put in the best "sarking" possible under the tin. We used Insulbreak 65 from Aircell. Also make sure you are well prepared with tarps (or your roofers are)...... My Mother-in law, who lives in the Gong, had her roof replaced a couple of years back and it turned in to a very messy and very costly job for the roofers and the insurance company..... Not to mention for my MIL  :Annoyed:

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## Bloss

> Most 180 to 200 m2 cottages have about 12 tonnes of roof tiles which is carried to the site on a rigid bodied truck, a conventional hip roof used to not require any other form of bracing as the hips were a sufficient form of bracing. This discussion has been talked about before & with modern designed trusses for tile roofs the trusses will not meet the uplift design criteria let alone the truss tiedown, could be different for an older truss design though, where the designs have not been designed to the bare limit.
> regards inter

   :What he said:  mea culpa! I must been off my medication (or on it!) concrete tiles are around 45kg/m2 to 60kg/m2 depending on tile design and lap - so not 40 tonne on average especially on older houses of smaller area. A bit of a Canberra focus there too - average newly constructed fee-standing Australian house size in 2011 was 243m2 - roof area will vary according to design of course, but that size would be around 15 tonnes. Average new free-standing house size in Canberra has been falling a little, but is still sitting at around 260m2 - and block sizes are heading south too. 
My take-away still stands -  
There is no 'general rule' nowadays I'd get it plugged it into a package and see what was needed - or get an engineer to do it. As I said in most places so far as I am aware you can't replace a tile with tin or vice versa without approval and they will require technical review of the roof frame specs - and perhaps walls too although unlikely.

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## David.Elliott

We're thinking of going down the same route soon...
Off the top of my head I cannot come up with anything I can tie wall plates to walls with.
They should be  strapped from 10 or more courses down the brickwork but cannot do that, lots of places, (cannot remember centres) building already there...
Rafters to wall plates, easy, diagonal bracing easy, but wall plates to walls not so...
My roof pitch is quite shallow too, which makes me believe that I cannot really overdo the tying down.
Any suggestions?
All help happily accepted... 
David

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## barney118

Firstly Bloss thanks for making me look like a goose with your 40t quote. Lol.  
David, I can recall when I did mine, firstly it depends on the wind category for your area. For N1 N2 I believe it's nominal fixing. When I added trusses the truss guys provided a tie down plan which was triple grips to rafters and a number of straps etc to certain places and speedbrace over them. I didn't use any brace over the existing conventional  roof, but probably should have put some speedbrace over it given its really easy. 
Since I had open walls I put straps on to wall and over done it on bott plates.   
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## David.Elliott

Thanks Barney, 
had to look for triple grips, they look the goods..
The roof is 70s and so is all hardwood, which in itself has a bit of weight.
The front roof line is 21m across x 7.5m as a single large expanse, with the peak along the 21m edge.... rest is not so easy... 
Just feel like I should figure out some way to fix wall plates better... 
The wind category is a great suggestion, never thought of that???
Now, off to find that out. 
I'm in Jarrahdale WA and so we get cold in winter, not so hot in summer, suggestions on insulation anyone?

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## barney118

My old roof is hardwood too and it eats power saws! I left my old 38x50 battens where they didn't clash with my new battens, I was going to use steel top hats but found timber easier to work with especially with foil clips with the insulation. My house is classed as N2 as there is no tie down onto the brickwork when it was built after the ww2. But today they would probably class the back as N3 as I am high and take a beating from the Sth as it is elevated and open.  
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## Bloss

> I'm in Jarrahdale WA and so we get cold in winter, not so hot in summer, suggestions on insulation anyone?

  Read the insulation handbook in the Forum library - if you are redoing roof then  use foil at least or blanket preferably then add batts in the ceiling - batts at R5 or better. This will give good winter & summer performance.

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## Wavenut

What would be more expensive - a colorbond or tile roof?

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## David.Elliott

We're running with zincalume corro I'd have to say it'd be a lot cheaper

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