ᐅ Mold on the basement windows after installing the screed

Created on: 26 Jun 2016 08:21
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merlin83
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merlin83
26 Jun 2016 08:21
Hello,

the situation is as follows:

The screed was installed on Monday/Tuesday this week. The basement windows were probably closed. On Friday, I was able to enter the building again and opened the roof windows on the upper floor for ventilation. On Saturday, I also opened the basement windows and noticed black and green mold on the plasterer’s formwork everywhere.

Is this normal? Serious? Very serious?

What should I do?

Best regards,

Melrin
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Sebastian79
26 Jun 2016 08:52
Completely normal – this is the worst time for screed, as you can basically only achieve an acceptable climate through mechanical drying.

I hope you only leave the windows open briefly?
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merlin83
26 Jun 2016 09:15
Sebastian79 schrieb:
Completely normal—it’s the worst time for screed because you basically can only achieve a somewhat normal climate through mechanical drying.

I hope you only keep the windows open briefly?
Thanks for the tip. No, I actually had them open the entire (and first) night. What is the best way to ventilate the construction site?
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Sebastian79
26 Jun 2016 09:25
Air the room intensively for about half an hour several times a day. Since this usually doesn’t work, you need to dry it mechanically.

For the screed, this type of ventilation is not suitable – you should avoid it.

By the way, it gets even worse if you use heating – or are you already doing that?
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merlin83
26 Jun 2016 09:34
No, fortunately not yet.

So I will close the basement windows again at night.

Why can’t I leave all the windows open during the day if it’s not raining?
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Sebastian79
26 Jun 2016 09:38
Because the screed then dries out only on the surface, cracks and excessive curling can occur.

The screed installer should have normally explained this to you...

And airing during the day would be bad anyway, as you would bring in even more moisture 😉. At this time of year, ventilate only in the evenings or at night – or (I repeat myself) use mechanical drying, which is the only proper choice.

If you aren’t using any accelerators, the screed now needs to cure for 21 days (at least for cement screed) and should be ventilated regularly.

Has the vapor barrier already been installed? If not, for an unoccupied attic, is there an appropriately sealed staircase in place?