ᐅ Click vinyl flooring and residual moisture in the subfloor: how significant is the risk?
Created on: 10 Oct 2024 00:22
J
Jschm88
Hi,
I’m quite desperate and looking for advice and maybe some reassurance.
We moved into our house last week. We installed the flooring ourselves, while the rest was done by contractors. Unfortunately, before the tiles and vinyl flooring were installed, I forgot to do a CM (calcium chloride) moisture test. I had actually planned to do it, but then our daughter was born, and with all the construction stress, I completely forgot about this crucial test. I still blame myself for that.
I’m very worried this will cause problems and I can’t enjoy our beautiful home. Between the screed being poured and the start (not the completion!) of the flooring installation (click vinyl and tiles, including grouting and baseboards, which I unfortunately sealed very tightly with silicone), there were about 14 weeks for the upper floor and even 19 weeks for the vinyl on the ground floor before tile installation began after 13 weeks.
Some technical details:
- Calcium sulfate screed, 60mm (2.4 inches) on the upper floor, 70-80mm (2.8-3.1 inches) on the ground floor
- Underfloor heating
- Click vinyl with MDF core on the upper floor, full vinyl on the ground floor, both with underlays for impact sound insulation and polyethylene (PE) foil underneath
- During the drying phase (April to July) we naturally ventilated and heated, but because it was extremely rainy and humid, the drying process was slow. We even used three construction dehumidifiers and three fans for an additional four weeks
- The site manager only measured surface moisture and considered it dry
- The screed installer is confident, but of course I haven’t received anything in writing
I know it’s my own fault and I blame myself the most.
My questions:
- I realize it’s just a guess, but how realistic is it that there is still enough moisture in the screed now to cause structural damage?
- What would be the worst case? Loss of the flooring? Mold? Is it possible to detect mold early on?
- Is there any way to measure moisture now to finally get some peace of mind? I can’t exactly remove flooring in the middle of a room…
- What would be the best course of action? Bringing in an expert? Waiting and monitoring?
Thank you all so much!
I’m quite desperate and looking for advice and maybe some reassurance.
We moved into our house last week. We installed the flooring ourselves, while the rest was done by contractors. Unfortunately, before the tiles and vinyl flooring were installed, I forgot to do a CM (calcium chloride) moisture test. I had actually planned to do it, but then our daughter was born, and with all the construction stress, I completely forgot about this crucial test. I still blame myself for that.
I’m very worried this will cause problems and I can’t enjoy our beautiful home. Between the screed being poured and the start (not the completion!) of the flooring installation (click vinyl and tiles, including grouting and baseboards, which I unfortunately sealed very tightly with silicone), there were about 14 weeks for the upper floor and even 19 weeks for the vinyl on the ground floor before tile installation began after 13 weeks.
Some technical details:
- Calcium sulfate screed, 60mm (2.4 inches) on the upper floor, 70-80mm (2.8-3.1 inches) on the ground floor
- Underfloor heating
- Click vinyl with MDF core on the upper floor, full vinyl on the ground floor, both with underlays for impact sound insulation and polyethylene (PE) foil underneath
- During the drying phase (April to July) we naturally ventilated and heated, but because it was extremely rainy and humid, the drying process was slow. We even used three construction dehumidifiers and three fans for an additional four weeks
- The site manager only measured surface moisture and considered it dry
- The screed installer is confident, but of course I haven’t received anything in writing
I know it’s my own fault and I blame myself the most.
My questions:
- I realize it’s just a guess, but how realistic is it that there is still enough moisture in the screed now to cause structural damage?
- What would be the worst case? Loss of the flooring? Mold? Is it possible to detect mold early on?
- Is there any way to measure moisture now to finally get some peace of mind? I can’t exactly remove flooring in the middle of a room…
- What would be the best course of action? Bringing in an expert? Waiting and monitoring?
Thank you all so much!
Our process was quite similar, and we moved in about a year ago; so far, everything has been fine. If you haven’t installed the baseboards yet, I’d recommend waiting a bit longer to allow any remaining moisture on the sides to escape if needed. This helped us in one area—not with the screed but with the bottom row of bricks between the damp-proof membranes, which was still drying out slightly.
We were advised by several sources to wait 1–2 years before installing the baseboards, as this allows for much quicker responses to moisture issues.
We were advised by several sources to wait 1–2 years before installing the baseboards, as this allows for much quicker responses to moisture issues.
Thanks for sharing your story. Unfortunately, everything is already installed and even sealed with silicone, so nothing can get through anymore :-D I just hope that there’s no issue, and if there is, KlaRa says I’ll notice it on the floor after some time. Maybe I’m also just itching to remove a baseboard at some point, we’ll see.
Jschm88 schrieb:
watch the floor. Enjoy the floor and think positively.
Update for everyone interested: On the ground floor, I had the entire floor removed and then replaced with glued vinyl. This was for reasons different from those previously described here.
However, underneath it was completely dry, no mold, not even on the baseboards. So this might reassure others experiencing similar issues. Best regards!
However, underneath it was completely dry, no mold, not even on the baseboards. So this might reassure others experiencing similar issues. Best regards!
ZWEIK GmbH21 Nov 2025 17:32Hello from Hockenheim, from ZWEIK GmbH,
if you want to install a topping on a heated substrate, a CM measurement is mandatory. Whether it’s cement screed or calcium sulfate/anhydrite — no covering can be applied without verified residual moisture. Only when the CM test confirms that the screed is ready for installation can you proceed properly.
Covering a screed that is still wet inevitably leads to damage, especially with calcium sulfate or anhydrite screeds. So make sure to have it tested, otherwise you’ll face problems later.
Best regards
ZWEIK GmbH, from Stefon
if you want to install a topping on a heated substrate, a CM measurement is mandatory. Whether it’s cement screed or calcium sulfate/anhydrite — no covering can be applied without verified residual moisture. Only when the CM test confirms that the screed is ready for installation can you proceed properly.
Covering a screed that is still wet inevitably leads to damage, especially with calcium sulfate or anhydrite screeds. So make sure to have it tested, otherwise you’ll face problems later.
Best regards
ZWEIK GmbH, from Stefon
Similar topics