ᐅ Waterproofing membrane on the foundation slab (concrete slab)
Created on: 24 Feb 2025 14:35
K
ketiv75Hello forum,
we are currently renovating an older building from the 1970s and have completely gutted it. On the concrete slab, we plan to install 60 mm (2.4 inches) of Kingspan foil-faced insulation, and then the underfloor heating on top of that.
Is it advisable or necessary to lay a waterproofing membrane (e.g., Börner Erika) on the concrete slab?
If yes, should this membrane also be extended up the walls?
Should the edge insulation strip for the underfloor heating be installed before or after the membrane?
Thank you very much for your answers.
we are currently renovating an older building from the 1970s and have completely gutted it. On the concrete slab, we plan to install 60 mm (2.4 inches) of Kingspan foil-faced insulation, and then the underfloor heating on top of that.
Is it advisable or necessary to lay a waterproofing membrane (e.g., Börner Erika) on the concrete slab?
If yes, should this membrane also be extended up the walls?
Should the edge insulation strip for the underfloor heating be installed before or after the membrane?
Thank you very much for your answers.
It definitely makes sense, especially if you can connect the wall waterproofing membrane to it. In this case, that might no longer be possible.
Always extend the membrane up the wall, theoretically up to the finished floor level. Also under any entrance doors or floor-to-ceiling windows (under the threshold profiles, up to the outer edge of the concrete slab). However, extending the membrane up the wall is always a bit tricky to do properly with the membrane itself – I used a different system where you can stick a connecting strip to both the wall and the membrane. This makes installation significantly easier.
Edge insulation strips are installed afterwards; they belong in the layer above the insulation so they also seal the gap (usually with the self-adhesive foil on the edge insulation strip).
If you want, I have at least two unused Erika membranes available that I can give away (for pickup only), if that helps you. It depends on where you are in TH (we are in West Saxony).
Always extend the membrane up the wall, theoretically up to the finished floor level. Also under any entrance doors or floor-to-ceiling windows (under the threshold profiles, up to the outer edge of the concrete slab). However, extending the membrane up the wall is always a bit tricky to do properly with the membrane itself – I used a different system where you can stick a connecting strip to both the wall and the membrane. This makes installation significantly easier.
Edge insulation strips are installed afterwards; they belong in the layer above the insulation so they also seal the gap (usually with the self-adhesive foil on the edge insulation strip).
If you want, I have at least two unused Erika membranes available that I can give away (for pickup only), if that helps you. It depends on where you are in TH (we are in West Saxony).
Hello Harakiri,
thank you very much for the detailed response.
All the walls have already been plastered. Should I apply a bituminous thick coating at the joint area on the wall to improve the adhesion of the waterproofing membrane?
I live in Erfurt. I need exactly 2 rolls.
thank you very much for the detailed response.
All the walls have already been plastered. Should I apply a bituminous thick coating at the joint area on the wall to improve the adhesion of the waterproofing membrane?
I live in Erfurt. I need exactly 2 rolls.
Having plaster already applied is not ideal, as in theory moisture could be drawn up behind the waterproofing by capillary action. However, if the house has not had significant moisture problems in the past, this should remain mostly a theoretical concern.
As mentioned before, I would recommend using a connection tape, folded in the middle, and adhesive both to the wall and the horizontal waterproofing membrane. Börner also offers this as EriKa connection tape – you will likely need it anyway to seal the lap joints of the membranes. I would stay consistent with the system and apply Böcoplast PM as an adhesion promoter on the plaster.
The two EriKa membranes are available – although they are already 2 years old, I believe and hope they are still fine. They have always been stored indoors. Let me know if you want to pick them up.
As mentioned before, I would recommend using a connection tape, folded in the middle, and adhesive both to the wall and the horizontal waterproofing membrane. Börner also offers this as EriKa connection tape – you will likely need it anyway to seal the lap joints of the membranes. I would stay consistent with the system and apply Böcoplast PM as an adhesion promoter on the plaster.
The two EriKa membranes are available – although they are already 2 years old, I believe and hope they are still fine. They have always been stored indoors. Let me know if you want to pick them up.
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