ᐅ Concrete slab with strip foundation and frost protection apron

wow... I didn’t receive an email notification and wanted to check if anyone had commented, and then I read through 4 pages full of useful information! Thanks!!

Our site manager wants to proceed as you described. We are building without a basement, using calcium silicate blocks and external thermal insulation composite system (ETICS). Here is a rough sketch of how it is planned:

If we want to fully formwork the slab on grade, it will cost about 4,000 more. That was only an estimate and the structural contractor would need to be asked. We don’t know the cost for insulating the slab on grade alone in this example. However, he thinks that, for instance, 4,000 spent on ETICS or the roof would be more beneficial. The slab insulation contributes only 0.5 to the overall energy value and is not needed for frost protection.

We are not working with a general contractor, so we would have to negotiate any extra costs with the structural contractor. How this would affect the structural calculations is, of course, a different matter.

Your example is image 2, and yes, that is usually more than sufficient because the heat loss downward is minimal. Additionally, you will almost certainly have insulation under the underfloor heating on the inside as well.

Perhaps I should add that in Schleswig-Holstein, ETICS constructions are rather exceptions: most buildings have clinker brick facades, followed by monolithically plastered Ytong (aerated concrete) facades in second place, and wooden houses in third. ---Then there is a long gap, and only occasionally Poroton with ETICS appears. Karsten

No, you don’t have to. The structure on the slab isn’t really relevant for the insulation of the slab.

Well, anyway. In practice, you hardly notice the absence of XPS boards under the slab and along the strip footing, since neither the floor nor the wall feels particularly cold. So, theory is gray, but life is colorful.

It’s like a weather map—the more red, the warmer it gets. In other words, heat loss without any insulation is the highest, and with insulation beneath the floor slab it is the lowest. A frost skirt is basically the middle ground.