Treated timber for sole plate?

dunny1234 · 4 Oct 2011

I'm building a toilet/shower building on my campsite. The bottom of the timber frame will be close to ground level. I'm thinking of laying my concrete slab, with the DPM underneath. Then bring the DPM up the sides of the slab, DPC on top, and then fix a treated soleplate on top. So, Slab - DPM - DPC - Soleplate.

What i'm thinking of doing is having a double soleplate. I'll fix a treated soleplate to the slab, with DPM & DPC underneath. I'll then lift timber frame panels in place and screw the untreated soleplate/frame to the treated soleplate. Effectively, giving me 2 soleplates, but the bottom soleplate thats nearest ground level being treated? Does this sound okay?

Thanks in advance

gregers · 4 Oct 2011

yep,but why not use treated timber for all of the wall.

dunny1234 · 4 Oct 2011

I'm just a bit worried about shrinkage, as i'm plastering the interior. I know treated timber will shrink quite a bit, and dont want it cracking the plaster?

^woody^ · 5 Oct 2011

IMO, this is a generally bad detail.

You should have no timber where it is likely to get constantly or persistently damp - and using treated timber wont help

I can't see why you want two sole plates when you could design it with one. Nor why you are having DPM exposed on the outside of a slab

And there are different types of wood treatment - some are more appropriate for regular limited damp than others

Deluks · 5 Oct 2011

I already told him this woods, but his mind seems made up.

dunny1234 · 6 Oct 2011

Sorry, Deluks. I have taken your advice on-board. Just one thing, everyone is telling me to go with a dwarf wall, and wrap the DPM from under the slab, and wrap up the side of the slab and under the first course of bricks.

But when mention about not using a dwarf wall, but still wrapping the DPM up the slab, but under the sole plate, people are saying this is a bad idea as the DPM will be damaged by the sun and the elements over time.

Surely, using both options the problem of the DPM getting damaged is the same? They're both exposed in some way?

Deluks · 6 Oct 2011

dunny1234 said:
Just one thing, everyone is telling me to go with a dwarf wall, and wrap the DPM from under the slab, and wrap up the side of the slab and under the first course of bricks.

Not great advice. As previously suggested, build dwarf onto slab, make 'swimming pool' over slab and inside wall, fill with screed.

If you don't want to use screed, and just use a concrete base, build the dwarf wall perimeter first, then use dpm onto sand over the compacted hardcore layer and lapped over the wall which should be min 150mm above ground (225 would be better, an extra course)

This perimeter wall will require it's own foundation though, as per ground conditions.

Where will the showering water go?

diynot

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Treated timber for sole plate?

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