Subsequent sealing of the ground slab

Hello everyone,

we built 10 years ago. The construction area is located in Mechernich in the Eifel. A few months ago, there were severe floods in this area. We were not affected by the direct flooding, but since the water apparently stood underground too long in front of the floor slab (no basement) due to the clayey soil, water eventually penetrated the screed through the window sills. The screed has now been dried. To be prepared for the next storm, we are currently having drains installed retroactively. Now to my question: does it make sense to additionally seal the insulation boards attached to the floor slab with bitumen and lay a dimpled membrane in front of it? Some pictures of the situation on site are attached.

Thanks in advance for your tips.

Regards

Björn

And where should the drainage discharge to?

Is there a sealing behind the insulation boards? A sealing on the insulation boards makes little sense. Often, the floor slab is soundproofed with insulation boards. This is technically incorrect. A sealing is required from the front edge of the floor slab up to at least 15 cm above the existing ground level. The insulation boards only serve to protect the sealing.

In order to design a functional building waterproofing, the component structure must be known in detail. The waterproofing layers themselves must be applied to the shell construction (concrete/masonry), not to the perimeter insulation. Additionally, there is the technically demanding point of waterproofing in the threshold/sill area of the terrace door. Here, too, details of the installation situation must be known. Presumably, sealing can only be done with liquid plastic, a job for a specialized company. The details must be planned in the sequence of materials, workflows, and connections. It may also be necessary to redefine the relevant water load case applicable to you and thus the requirement for waterproofing according to [DIN 18195].

An additional drainage only makes sense if the drainage actually drains the building and the drainage water can be discharged in a targeted manner. Since the prescribed infiltration on the property will probably not work due to the presumably high groundwater level, it may be necessary to apply to the municipality for the discharge of drainage water into the sewer system.

I advise an inventory assessment by an expert and corresponding independent specialist planning. The planning of the details should not be left to the executing companies.

independent expert planning. The planning of the details should not be left to the executing companies.

+1

The sealing layers themselves must be applied to the shell construction (concrete/masonry), not on the perimeter insulation.

That's exactly right. Unfortunately, this is repeatedly carried out incorrectly by construction companies. What the pictures document here is to seal against accumulating seepage water. So according to DIN 18195-6.