Edge insulation on stone foundations

[Coll659]

Hi again. 

 

Renovating an old house and have followed the advice of people here on my other threads in regards to the floor but need some advice on how to deal with the insulation around the edges. 

It's an old house with stone foundations,  100mm concrete on top of the stone followed by an old doc and the solid walls. 

 

I have dug out all the old stuff until I got to solid ground and now building up as follows: 

 

Sand blinding

30mm eps

Dpm

200mm insulation

Underfloor heating foil

Underfloor heating pipes and rebar

100mm concrete 

 

My question is how to deal with the edge insulation on the uneven stone foundations. 

Do I just build up the insulation, pull the dpm against the insolation and fill the area behind with either sand or expanding foam, then some 30mm eps on top and on the wall with the Dpm behind it. (photo below shows a mockup of my idea, the orange EPS represents the concrete and the area with the wrapper is where I would put sand or foam, the bin bag being the Dpm of course? ) 

 

Any advice would be greatly appreciated

[Nickfromwales]

Both of the 100mm layers of insulation would just push up as hard against the foundation as you can, so the upper layer there looks like it could slide over by nearly 100mm for eg. You don't need expansion for anything other than the heated slab, so again the 25mm perimeter insulation (with an additional 10mm expansion foam skirt in front of that), sorts that.

[Coll659]

Thanks nick. So air gaps between the insulation and stone foundations are not an issue then? 

[Nickfromwales]

24 minutes ago, Coll659 said:

Thanks nick. So air gaps between the insulation and stone foundations are not an issue then? 

Nope. The only outward force will be from your heated slab potentially expanding, but below that everything sits where you put it and stays there.