Foundation Design

ahjasus

I need an solution to an as-built problem with the concrete slab foundation of my new timber frame house.

At the moment my slab foundation extends 230mm beyond the wall line. Therefore water is sitting on the slab rather than running off. I want to solve this problem and also close the cold bridge that the over-extended slab is creating into the house.

I have come up with two possible solutions and would really appreciate some advise on the merits of these and also any alternative suggestions.

Please don't ask how it got like this - it just is, and I'm only interested in solutions.

Option 1: Cut away the concrete slab to a depth of 150mm, insert 100mm insulation to top and sides of slab. Fix DPM to underside of weather membrane and extend downwards to cover insulation and slab. This is going to be awkward and expensive to cut away but if its the only option then I will do it.

Option 2: Insulate top and sides of existing slab. Fix timber moulding to create diagonal run-off at point where insulation and wall meet. Fix DPM to underside of weather membrane and extend to cover moulding, insulation and slab. This seems like a simple solution but leaves the timber sole plate below the level of the DPM.

I appreciate that this may not be 100% clear. I can clarify and post sketches if necessary.

All advice greatly appreciated.

Civil Eng

Hi,

PM me a few sketches and I'll take a look at it and see if I can help.

ahjasus

HI Civil Eng...sorry for not responding to your message, self builds and years go by! - I have PM'ed you a sketch.