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Wood options for timber roof.


MarkH
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In terms of the wood varieties you can build a roof with, what have people used and why?

Our original plans specified green oak, the architect told us it was all the rage at the moment as if that was a selling point. The dimensional instability of oak puts me off a bit, I rented a new oak build in France for a few months that was almost on the other side of the road by the time we moved out.

A friend is building the trusses and he seemed to think most hardwoods could be made to work and it's all down to the sizing of the beams. Douglas Fir has been mentioned. One gable truss might be exposed to the weather, depending on how we glaze it - I guess that's significant as we wouldn't want to use anything that had to be treated or otherwise maintained.

All thoughts appreciated.

 

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Hello Mark. Welcome...............Have a look at thisScreenGrab.gif

If you meant how do you make the roof material out of wood, rather than the make the timbers out of wood (and then slate it) , then I hope this will help.

You'll see that our plan is to make the roof out of wood: the south face (the one you can see) has a tray of solar PV, (about 10 panels) and some glass over an internal garden area. I am making all the shakes for the roof myself, mainly because we can't afford to buy them (or have decided to afford other things instead, take your pick). Oak shakes from Vincent Timber are about £100 per square meter. We are using shakes, not shingles. I can buy oak locally very cheaply indeed (The local  timber merchants turn oak into firewood - I am not joking). Here's what it all costs

There are two main issues

  • Roof pitch
  • Roof material

The pitch is about 25 degrees. A bit low for shakes. The water needs to run off quickly. So, we've decided to make the roof cosmetic, and to make the roof entirely water and wind-tight using some other materials. Not sure which yet. I hope to have dried enough oak ready (or have bought enough dried oak) to make our own oak beams. But I fear that the U value of oak is a good argument not to do that. Pity, because it looks really nice.

With wooden roofs the material has to be one which has a high tannin content - tannin preserves it. So it needs to be made of Western Red Cedar, or Oak, or Larch or Sweet Chestnut.

I think your friend is correct. Most hard woods will do for the timbers. But they must be dry (below 17% I think).

Good luck with the build.

Ian

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You can't afford to expose a truss to the weather, anything except balsa wood will do, I would not use green oak but you already know the downside. You will likely finish up with softwood (when you find out the prices)

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Douglas fir is highly thought of for structural work and can be quite sensibly priced. It should be 'moderately durable'.

 

Why not have a play around on www.iwood.co.uk to compare the different species available (NB I haven't actually bought anything from them but found their online pricing was a useful benchmark).

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Thanks Ian - your design looks great, what did you use to produce that model? Yes I am considering something similar to you (although my question was more about truss materials, vaguely worded though). We're tucked away in the woods here which we like but I was disturbed to see, whilst out on a boat a while ago, that you can see our caravan from miles away! I'd like to modify our inherited (from previous owners) design specifically with respect to the appearance of the building which in the approved plans is rough rendered and white. It'd be good to blend into the surrounding landscape a bit more and I've considered larch cladding on the seaward side which with the woodland backdrop would render us invisible! Wood 'tiles' would be good too but my knowledge of those is minimal, so thanks. Our planning permission contained several spurious references to the 'vernacular' though so whether we'd get away with not using slates as specced is questionable, we're already pushing our luck with changes we've made.

14 hours ago, tonyshouse said:

You can't afford to expose a truss to the weather, 

Why not? Aren't many glazed gable ends exposed?

14 hours ago, Crofter said:

Why not have a play around on www.iwood.co.uk to compare the different species available (NB I haven't actually bought anything from them but found their online pricing was a useful benchmark).

That is a good website.

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22 hours ago, Crofter said:

Why not have a play around on www.iwood.co.uk to compare the different species available (NB I haven't actually bought anything from them but found their online pricing was a useful benchmark).

Thanks Crofter. This is  exactly the sort of information which we need to collate and keep as a central resource. As the Americans say " Good jaaaab man"

Ian

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  • 7 months later...
On 5/26/2016 at 08:11, Crofter said:

Why not have a play around on www.iwood.co.uk to compare the different species available (NB I haven't actually bought anything from them but found their online pricing was a useful benchmark).

 

I had a play around on iwood.co.uk - it's a very good website for comparison of species and general pricing up. I then went to my local mill who were helpful but didn't have very 'green' green oak or douglas fir so I looked further afield and got some high prices compared to iwood. I phoned them, had a long chat with a couple of the people there and ordered the timber for our trusses three weeks ago. After good and clear comms from iwood It arrived today. All seems well. It is very heavy.

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  • 2 months later...
On 27/01/2017 at 07:44, Crofter said:

Glad it worked out, keep us posted with your project :)

 

Trusses done. Here's one of them (kingpost yet to be cut down, by the way). I might leave those dog footprints...

 

DSC_0688.thumb.JPG.b514a37d476062e0e569ea29e9f3f871.JPG

Edited by MarkH
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