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Baumschubser20 Dec 2025 09:20Dear community,
We bought a house last year and carried out extensive renovations. However, there are still a few issues.
The frames of the new door windows we had installed are not as deep anymore, which has left a gap visible between the window and the terrace. The window installer referred us to the roofer, but we did not need a roofer during the renovation. The question now is how to properly fill this gap. I have already done some work with expanding foam, but how should I proceed from here? The area is covered by a pergola, and the terrace slabs are level with no slope. My impression is that the expanding foam from the grey tube should be removed, then a thin construction board placed in front, followed by filling with concrete screed, and finally sealing the joint to the window frame with silicone. Does this approach make sense, or am I completely off? I would appreciate your advice.
Best regards,
Daniel
We bought a house last year and carried out extensive renovations. However, there are still a few issues.
The frames of the new door windows we had installed are not as deep anymore, which has left a gap visible between the window and the terrace. The window installer referred us to the roofer, but we did not need a roofer during the renovation. The question now is how to properly fill this gap. I have already done some work with expanding foam, but how should I proceed from here? The area is covered by a pergola, and the terrace slabs are level with no slope. My impression is that the expanding foam from the grey tube should be removed, then a thin construction board placed in front, followed by filling with concrete screed, and finally sealing the joint to the window frame with silicone. Does this approach make sense, or am I completely off? I would appreciate your advice.
Best regards,
Daniel
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nordanney20 Dec 2025 09:26Baumschubser schrieb:
The window manufacturer referred us to the roofing subcontractor, but we didn’t need a roofer as part of the renovation. Finally, a good window manufacturer. Yes, involving the roofer is a great idea for proper waterproofing. Everything else is technically incorrect and botched.Hi Daniel,
In the picture, it is quite clear that the foam is basically just a gap filler and is currently exposed, which won’t hold up long outdoors. Your idea is roughly on the right track, but screed up to the frame is exactly where cracks tend to develop later on, even if it feels solid at first. The gray strip looks like a drainage guide; you definitely should not embed it in concrete, otherwise water will accumulate where it shouldn’t. It would be better to cut back the foam neatly, place a narrow rigid board as lost formwork in front, and then fill mineral-based material with a clear separation from the frame. The joint itself should remain flexible; silicone is possible but ages quickly, while MS polymer often lasts 8–10 years and discolors less. Even under a pergola, there is enough moisture.
I’m also curious: what is the height difference from the bottom of the window to the terrace—more like 10mm (0.4 inches) or closer to 40mm (1.6 inches)? And does the paving slope away from the house or is it rather level? That factor is more important than the material used.
In the picture, it is quite clear that the foam is basically just a gap filler and is currently exposed, which won’t hold up long outdoors. Your idea is roughly on the right track, but screed up to the frame is exactly where cracks tend to develop later on, even if it feels solid at first. The gray strip looks like a drainage guide; you definitely should not embed it in concrete, otherwise water will accumulate where it shouldn’t. It would be better to cut back the foam neatly, place a narrow rigid board as lost formwork in front, and then fill mineral-based material with a clear separation from the frame. The joint itself should remain flexible; silicone is possible but ages quickly, while MS polymer often lasts 8–10 years and discolors less. Even under a pergola, there is enough moisture.
I’m also curious: what is the height difference from the bottom of the window to the terrace—more like 10mm (0.4 inches) or closer to 40mm (1.6 inches)? And does the paving slope away from the house or is it rather level? That factor is more important than the material used.
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