# Forum Home Renovation Sub Flooring  stirup advice - bush poles & concrete footings

## Douglas Fur

Hi All, 
I live on a rural property with extensive areas of bushland. I'm in the process of knocking up a rustic under-cover area to store items out of the rain/sun. I have saved a few previously felled stringy bark trees and de-barked the trunks for use as posts. The diameters of each post are roughly 300mm. Can any one advise the simplest way to mount the posts to the concrete footings? I have seen simple methods using 'L' shaped brackets bolted to both pole & concrete and others where stirups  are used to slide up into a cut made into the bottom of the post. 
For my mind the 'L' bracket method looks easiest, but I'm not sure how this would stand up to wind forces?? Bear in mind this shelter is in bush and is not intended for council or bulding reg's 
Thanks

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## intertd6

Any hold down system you use to attach posts to concrete will need bracing panels to resist wind loads as the post attachment has none, probably the cheapest method would be concrete bored pier, large angle fixed to pier with cast in HD bolts, slot cut in post over angle with 12mm bolts passing through the lot. 
regards inter

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## ringtail

you could use a blade styrup like they do on big section square posts

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## woodchip

Have a look at these Pryda post supports, can basically go to any size post. used them recently on 190x190 posts, used 1 on each side of the post, so that is 4x fixings into the concrete, with anka screws or similar.  Viewpoint Media Player  
cheers

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## Moondog55

Are the pads there yet?
If not; perhaps a decent sized Coach screw ( 25mm and as long as you can afford )  into the centre of the post would work, I seem to remember this being mentioned in the "Whole Earth " magazine years ago, balance the pole on a couple of  90*45s over the hole, brace well and  then pour the concrete

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## SilentButDeadly

> Any hold down system you use to attach posts to concrete will need bracing panels to resist wind loads as the post attachment has none, probably the cheapest method would be concrete bored pier, large angle fixed to pier with cast in HD bolts, slot cut in post over angle with 12mm bolts passing through the lot.

   :What he said:

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## Uncle Bob

> Are the pads there yet?
> If not; perhaps a decent sized Coach screw ( 25mm and as long as you can afford )  into the centre of the post would work,

  Nah, just do what real bushmen/farmers do. Use number 8 wire and staples  :Smilie:

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## Bloss

> 

   :Wat they said:  too - coach screw not sufficient although 300mm diameter HW take a lot of lifting - but wind can lift a lot! More critical will be tying the roof down, whatever it is made of - so the battens/rafters and the cladding. For that the only half-joking suggestion of UncleBob's 8g wire and staples can be useful. The angle brackets or Pryda supports of suitable size will work too.

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## Moondog55

Surely the strength of a 25mm coach screw is as great as the 25mm tubing on a standard stirrup post.
It is after all only there to hold the post down into the concrete and resistance to uplift would be provided by a 50mm square washer, is it that the screw thread isn't a good enough connection to the timber? 
Must admit it is a long time since I actually saw a one inch coach screw and these are the only suppliers I found in a quick google search  Tree House Lag Bolts | Heavy Duty Lag Bolts | One Inch Diameter Lag Bolts | Tree House Supplies 
Mates used them when making a big pole house back in the 70s

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## Bloss

The shear strength of the screw (if you could source one . . .) would be much the same - the problem is the screw into the timber as you say. Aside from the little matter of not complying with BCA.

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## Moondog55

BCA and Bush shelter in the same sentence?
Looking back on all the pole sheds i have seen on farms and country properties over the years I don't think I have ever seen one that was actually tied into the ground, mostly they sat the poles on a big rock to get the end of the pole out of the dirt. 
OP did say compliance wasn't an issue 
If the pads have already been poured then the uplift resistance will rely on the strength of the bolt that is holding the bracket, my past experience says this is not as strong as a threaded rod cast in place. 
The pryda site has some very good data  http://www.pryda.com.au/media/fckupl...uly%202010.pdf

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## watson

Pardon me for stepping in.......although the OP said basically no rules apply, as far as council etc....I figure the rules of sensible construction methods apply and from experience I know that coach screws don't handle it.
Woke up one morning to find an entire 4 x 6 shed outside the back door.... upside down. Never ever found the coach screws (I will one day when a tyre goes flat).
I'd go with Bloss in this case.

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## Bloss

As Noel says - I wasn't mentioning the BCA as being required in this case, but they are minimum requirements and this type screw fixing wouldn't cut it. Wind doesn't care about BCA compliance - it will lift a rough construction in the bush or in an urban area just the same . . . 
I grew up in the bush and saw many a shed swap positions in full or in part - often after having been in place and in use for decades with no apparent problem - until the right bit of wind came along! Over some amazing distances too. All the pole sheds I built and have seen have the poles well into the ground - the better ones concreted, but more often simply buried, but usually well in - minimum 25% in an 75% out, more often 1/3 in ground (depending on scale of structure too). Biggest design and build failure in country sheds IMO was lack of bracing - mostly fine if always stacked to the gunnels with hay, but the cause of much leaning when empty - usually away from the prevailing winds.

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## Moondog55

Point taken. 
And I do take the point about a coach screw not being sufficient, but what is the stripping strength of a hardwood post/ screw thread interface?
Not trying to start a fight either, looking to learn so I can avoid mistakes.
I was under the impression that a concreted in threaded rod or bolt was preferable to to a Ramset placed after the concrete has set.

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## Gaza

> I was under the impression that a concreted in threaded rod or bolt was preferable to to a Ramset placed after the concrete has set.

  thats an open end question, 
if the thread rod was bent over and tied into the reo cage or just stuck in the wet concrete. if using chemset this can be stronger than concrete but you need to have the right holes size, correct depth and actual clean the dust out of the hole,  
dyna bolts are another area of discussion but thats for another day. 
we are actual all taking out of @@@@ on this one cause we can not calulated the size of footing or hold down required without knowing the height of the posts and the roof load this is important to calulate the hold down requiremnts. 
further note to this whole posts shoe and coach screws please dont use roofing screws even for 90x90 posts as they dont have an shear strength

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## Bloss

> Point taken. 
> And I do take the point about a coach screw not being sufficient, but what is the stripping strength of a hardwood post/ screw thread interface?
> Not trying to start a fight either, looking to learn so I can avoid mistakes.
> I was under the impression that a concreted in threaded rod or bolt was preferable to to a Ramset placed after the concrete has set.

  Gaza raises some good points too - as to any type of screw into HW. Depends on green or seasoned as well as type and a bunch of other issues. Likewise with threaded rod or bolts vs loxins or ankascrews etc. This is not an estimation game - most people, even those in trades, IMO and experience underestimate all sorts of forces and the need to tie a whole structure together. So it is not uncommon to see good footings and frame then a single (too short or light) screw or skewed nails holding battens down; or see well built structure above ground, but in post holes way too shallow, too small, rounded at the bottom or in soft soils - so as to allow it to be lifted fully from the ground. Even otherwise over-engineeed structures need only have one bit under-specced or built and problems can happen. But of course catastrophic winds or other events are not all that common in most places so most times we get away with it.

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## tunagirll

> Gaza raises some good points too - as to any type of screw into HW. Depends on green or seasoned as well as type and a bunch of other issues. Likewise with threaded rod or bolts vs loxins or ankascrews etc. This is not an estimation game - most people, even those in trades, IMO and experience underestimate all sorts of forces and the need to tie a whole structure together. So it is not uncommon to see good footings and frame then a single (too short or light) screw or skewed nails holding battens down; or see well built structure above ground, but in post holes way too shallow, too small, rounded at the bottom or in soft soils - so as to allow it to be lifted fully from the ground. Even otherwise over-engineeed structures need only have one bit under-specced or built and problems can happen. But of course catastrophic winds or other events are not all that common in most places so most times we get away with it.

  I am sure by now the OP has made his shed, but for the purpose of anyone else who searches for something similar will add 2 cents for what it's worth  :Smilie:  
I've worked in construction fasteners for Ramset for 15 years now and I think the most fundamental misunderstanding most people have is the assumption that fasteners need to adhere to some kind of Australian Standard for performance. There is no AS for capacity of anchors. Most of them are going to be fit for purpose but you are totally reliant on the quality the manufacturer puts in. Any brand that load rates its products and publishes the data is what you are going to need if you want to be sure of what your fitting is going to hold. 
Coach screws are a common fit-for-purpose fixing but also one of the ones most likely to be cheaply and poorly made because they aren't a product that is normally sold into any kind of engineering trade. I don't know of any brand that sells coach screws by themselves with any kind of load rating. So yes you can use them but you have to be aware that you won't really be able to know what your particular coach screws will hold. Never assume that a load capacity for steel bolts to the same thickness is what you will get out of a coach screw.

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## Bloss

All good points - thanks. My point was more that coach screws of _any_ quality are not fit for many of the purposes I have seen them used for - they have their uses, but are not to replace bolts or anchors. In particular I have seen them used dangerously in masonry as though they were AnkaScrews Ramset Australia

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