ᐅ Basement waterproofing: slurry waterproofing or bitumen membrane

Hi,

I’ll keep it brief – hopefully not too brief.

Current situation: House built in 1996, exterior waterproofing with thick bitumen coating plus XPS insulation applied this summer (original waterproofing was faulty). Horizontal damp-proof course exists in the basement masonry.

Clay soil – after heavy rain, the house is surrounded by water. No water gets inside, except at one spot where the connection between the foundation and the concrete floor is not completely sealed. I plan to install a fillet joint there.

A soakaway pit was built to reduce hydrostatic pressure. Groundwater level is 6 meters (20 feet) deep.

Task: Waterproofing the basement floor against soil moisture.

I planned to start next week with a waterproof slurry coating and seal the basement floor inside up to the level of the horizontal damp-proof course.

Now I’m reading that waterproof slurry coatings are vapor-permeable. Previously, a bitumen membrane was welded on – but it was destroyed during the investigation of the water ingress cause.

The floor build-up will be PIR/PUR insulation + vapor barrier + underfloor heating + flowable screed.

Waterproof slurry coatings are widely praised for easy internal waterproofing. But if they are vapor-permeable, won’t water penetrate over the years? Or am I missing something?

Thanks for reading and your input.

I'll answer myself: My current understanding is that waterproof slurry is not suitable. I will install a cold-applied bitumen membrane in the basement. I need a vapor barrier that is impermeable to diffusion. This must be connected flush to the ring beam and the external waterproofing. That way, the basement will remain dry.