Dear forum,
As part of a renovation, our raised basement was uncovered and (hopefully correctly) coated with a new two-component liquid waterproofing membrane (cleaning, removing protrusions, correcting the fillet, grinding off the foundation overhang, sanding the foundation edge due to cement residue, priming with bituminous primer 901, scratch coat with 2K liquid waterproofing membrane, 3 mm (0.12 inch) wet layer of 2K liquid waterproofing membrane, fabric reinforcement, second layer with 3 mm (0.12 inch) wet thickness of 2K liquid waterproofing membrane).
Now, the corresponding 24 cm (9.5 inch) perimeter insulation (XPS, tongue-and-groove, glued at the joints) and base insulation (XPS, straight edge) are to be installed, as long as the wall temperature remains above 5°C (41°F) (full surface application with 2K liquid waterproofing membrane, possibly using the buttering and floating method, if there are significant unevenness issues). As I understand it, this should not be a problem because the wall temperature in the adhesive area should actually rise due to the insulation.
The perimeter insulation is 24 cm (9.5 inch) thick (tongue-and-groove). Unfortunately, the base insulation was not available in this thickness from my building materials supplier (limited supplier network), so I could only get it in 12 cm (4.7 inch) thickness and need to install it in two layers. Here, I probably cannot apply the second layer with the 2K liquid waterproofing membrane, since the surface would then be exposed to the outside temperature, correct?
I was already advised that we must ensure the waterproofing membrane is fully and evenly dried.
There will then be weather protection (rain and UV) provided by tarpaulins (200 µm). These are appropriately long (about 4 m (13 feet), and attached at a maximum height of 2 m (6.5 feet) above ground level, so there is a considerable overhang beside the trench. The tarpaulins are weighted down to prevent them from blowing away.
Now, it would be better not to reinforce the base insulation, right? Because the surface temperature would then become too low. Another point I was told, if no reinforcement is applied immediately, is that a thermally decoupled zone between the wall and the unprotected insulation could develop, allowing moisture to accumulate for longer. Unfortunately, I did not understand this point and would appreciate a brief explanation (maybe even with a drawing?). Due to the sloping site of the building, we also make use of the fact that the base insulation boards may extend slightly below ground level, although I wonder whether securing the base boards in the soil with a mineral waterproofing slurry would be advisable.
Installing the perimeter insulation would have the advantage that the drainage could still be laid and at least partially backfilled. This drainage would then end in a sump, from which I could (temporarily) pump out the drainage water.
I am also somewhat concerned about leaving the strip footing exposed during the cold season (last weekend it got significantly colder, so I at least placed insulation boards in front of it).
What do you think?
As part of a renovation, our raised basement was uncovered and (hopefully correctly) coated with a new two-component liquid waterproofing membrane (cleaning, removing protrusions, correcting the fillet, grinding off the foundation overhang, sanding the foundation edge due to cement residue, priming with bituminous primer 901, scratch coat with 2K liquid waterproofing membrane, 3 mm (0.12 inch) wet layer of 2K liquid waterproofing membrane, fabric reinforcement, second layer with 3 mm (0.12 inch) wet thickness of 2K liquid waterproofing membrane).
Now, the corresponding 24 cm (9.5 inch) perimeter insulation (XPS, tongue-and-groove, glued at the joints) and base insulation (XPS, straight edge) are to be installed, as long as the wall temperature remains above 5°C (41°F) (full surface application with 2K liquid waterproofing membrane, possibly using the buttering and floating method, if there are significant unevenness issues). As I understand it, this should not be a problem because the wall temperature in the adhesive area should actually rise due to the insulation.
The perimeter insulation is 24 cm (9.5 inch) thick (tongue-and-groove). Unfortunately, the base insulation was not available in this thickness from my building materials supplier (limited supplier network), so I could only get it in 12 cm (4.7 inch) thickness and need to install it in two layers. Here, I probably cannot apply the second layer with the 2K liquid waterproofing membrane, since the surface would then be exposed to the outside temperature, correct?
I was already advised that we must ensure the waterproofing membrane is fully and evenly dried.
There will then be weather protection (rain and UV) provided by tarpaulins (200 µm). These are appropriately long (about 4 m (13 feet), and attached at a maximum height of 2 m (6.5 feet) above ground level, so there is a considerable overhang beside the trench. The tarpaulins are weighted down to prevent them from blowing away.
Now, it would be better not to reinforce the base insulation, right? Because the surface temperature would then become too low. Another point I was told, if no reinforcement is applied immediately, is that a thermally decoupled zone between the wall and the unprotected insulation could develop, allowing moisture to accumulate for longer. Unfortunately, I did not understand this point and would appreciate a brief explanation (maybe even with a drawing?). Due to the sloping site of the building, we also make use of the fact that the base insulation boards may extend slightly below ground level, although I wonder whether securing the base boards in the soil with a mineral waterproofing slurry would be advisable.
Installing the perimeter insulation would have the advantage that the drainage could still be laid and at least partially backfilled. This drainage would then end in a sump, from which I could (temporarily) pump out the drainage water.
I am also somewhat concerned about leaving the strip footing exposed during the cold season (last weekend it got significantly colder, so I at least placed insulation boards in front of it).
What do you think?
L
LComputer2 Dec 2025 15:49Hello everyone,
Thank you very much for the detailed and very helpful answers!
One small question comes to mind:
How do I connect to the cove molding? Chamfering the panels is clear, but this will never allow them to fit perfectly against the waterproofing membrane; on the other hand, applying more waterproofing membrane (as adhesive) at this point is not effective either, as it would alter the shape of the cove molding.
Thank you very much for the detailed and very helpful answers!
One small question comes to mind:
How do I connect to the cove molding? Chamfering the panels is clear, but this will never allow them to fit perfectly against the waterproofing membrane; on the other hand, applying more waterproofing membrane (as adhesive) at this point is not effective either, as it would alter the shape of the cove molding.