Hello everyone,
Our house has a basement constructed with a waterproof concrete shell ("white tank"). The groundwater level on our property is very high, so this was necessary. We are working with a general contractor (GC).
After completing the basement, we hired an expert to evaluate the construction execution. In their report, the expert criticized that the perimeter insulation was only partially fastened with mechanical fixings, whereas according to the applicable DIN standards, it must be secured continuously.
We immediately forwarded the report to our GC and repeatedly requested that the insulation be properly fastened. However, our GC completely ignored this and instead backfilled the area.
This raises the following questions for me:
- What impacts and consequences could result from the missing mechanical fixings?
- How extensive is the work needed to add these fastenings later on? Is it even possible? Secant piles were necessary during the basement construction to keep the groundwater out, and those are now obviously no longer in place.
- What is the best way to handle this situation with our GC? Established standards were ignored, and we pointed out the defect in a timely manner (before backfilling was done).
Thank you for your experiences and advice.
Our house has a basement constructed with a waterproof concrete shell ("white tank"). The groundwater level on our property is very high, so this was necessary. We are working with a general contractor (GC).
After completing the basement, we hired an expert to evaluate the construction execution. In their report, the expert criticized that the perimeter insulation was only partially fastened with mechanical fixings, whereas according to the applicable DIN standards, it must be secured continuously.
We immediately forwarded the report to our GC and repeatedly requested that the insulation be properly fastened. However, our GC completely ignored this and instead backfilled the area.
This raises the following questions for me:
- What impacts and consequences could result from the missing mechanical fixings?
- How extensive is the work needed to add these fastenings later on? Is it even possible? Secant piles were necessary during the basement construction to keep the groundwater out, and those are now obviously no longer in place.
- What is the best way to handle this situation with our GC? Established standards were ignored, and we pointed out the defect in a timely manner (before backfilling was done).
Thank you for your experiences and advice.
Lumpi_LE schrieb:
What kind of standard is that supposed to be? (It should be mentioned in the report)
Anchoring insulation against the soil is kind of nonsense; your general contractor probably thought so too. No, it’s not nonsense but actually required according to DIN standards, especially in cases with groundwater. In the worst case, your entire insulation could be pulled off otherwise.
BUT: as is often the case, theory and practice differ. According to the manufacturer's instructions, it should also be fully glued. Has that at least been done?
In our project, no bitumen or adhesive was used. It was only anchored with dowels. I wasn’t really happy about that either, since it wasn’t according to the regulations. But everything is fine, no problems 🙂 I have also seen other construction sites where it was done the same way. It definitely holds better than just gluing, but I wouldn’t have minded bitumen as a secondary safety measure...
I would say the same for your case: just leave it as is. What could be missing now if it is glued, partially anchored with dowels, and already backfilled?
Do you maybe still have a picture? Then I can take another look!
Lumpi_LE schrieb:
What kind of standard is that supposed to be? (It should be mentioned in the report.)
Attaching insulation to the ground is quite pointless; your general contractor (GC) probably thought so too. DIN 18550 / DIN 13914
Bookstar schrieb:
No, that’s not nonsense but actually required according to DIN. Especially in cases with groundwater. In the worst case, otherwise, the entire insulation could be pulled off.
BUT: as often, theory and practice differ. According to the manufacturer’s instructions, it must also be fully glued. Has that at least been done?
In our case, no bitumen or adhesive was used. It was only mechanically fastened. I didn’t really like that either, as it wasn’t according to the regulations. But everything is fine, no issues 🙂. I have also seen other sites where it was done like that. It definitely holds better than just gluing, but I wouldn’t have refused bitumen as a second safety measure...
I would also say in your case, leave it as is. What could be missing now if it’s glued, partially fastened, and already backfilled?
Do you maybe have a photo? Then I can take another look! Thanks for your detailed response and assessment. That already helps me a lot. Attached is a photo where our expert has marked the areas where the insulation was fastened. Unfortunately, it’s not very clear.
What bothers me most is that our GC simply does not respond at all and will eventually backfill. On the third inquiry, the answer was "the boards must not be mechanically fastened." Again, our expert explicitly pointed out on follow-up that this is nonsense.
TobSte20 schrieb:
DIN 18550 / DIN 13914It’s not mentioned there.Bookstar schrieb:
required according to DINCan you specify according to which one?I still maintain that this is simply not true.
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