Foundation detail for timber extension

12 Jun 2016
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United Kingdom
howdy all.

I was wondering which foundation to use for a timber single storey extension, roughly 3m X 3m. I was edging towards a raft but I'm struggling to design the detail of the sole plate. And disguising the edge of the raft above ground level.

There is no brickwork skin. I was going to design the raft with compacted hardcore, blinding sand, Dom,100mm ridged insulation and 100mm concrete.

That way fixing through the sole plate won't pierce the dpm. However in struggling to hide the concrete below the timber framing. I was thinking of using a ridged insulation on the external face of the timber and dropping it down 50mm over the concrete/timber joint and then k-rend'ing it.

Any suggestions?
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It's not difficult, but you will see something below the frame and above the ground level, so if not concrete, then you need to decide what that something will be and just stick it on the face of the shoe or edge beam.

Fixing through DPC/DPM below the plate won't be an issue.

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