ᐅ Is insulation necessary for masonry in contact with the ground?

Hello,

we are currently building an urban villa with an extension. Due to some differences in height, the extension with the granny flat is 50cm (20 inches) lower. There are two areas on the extension where soil will be up to about 40 to 50cm (16 to 20 inches) high along sections of approximately 4m (13 feet) each.

So far, two coats of waterproof slurry have been applied, followed by two layers of Remmers building sealant. The question now is, what should the next steps be? My plan was to install a dimpled membrane before backfilling with soil. However, I am now less concerned about moisture and more worried about a thermal bridge. Could this cause mold to develop on the inside of the wall?

We built with 36.5cm (14 inches) Ytong blocks.

Everything is correct so far! Waterproof slurry protects against hydrostatic water pressure, and dimpled membrane (also called drainage membrane) serves as a mechanical protection for the waterproofing. The key term here is perimeter insulation, which obviously makes sense in this context.