ᐅ Applying joint compound to gypsum fiberboard before the screed has fully dried?

Hello everyone,

Is it possible to start applying filler to gypsum fiberboards before the screed has been fully heated up? At the moment, the house isn’t particularly humid. So, the idea would be to apply the filler first, and once it has cured and dried, then begin heating the screed. Or is it only acceptable if the humidity isn’t too high during the filling process?

The screed is calcium sulfate, installed 1.5 weeks ago. Unfortunately, the heating system isn’t ready yet to start the full heating process, and I don’t know when it will be. Therefore, the plan is to fill the gypsum fiberboards in about a week and only start the heating program once the filler has dried.

Thank you very much

You can apply filler. That works. Ventilate well and everything is fine.

I would not agree with that...
In our case, the drywall finishing (jointing) was done only after the heating-up program, specifically a full 6 weeks after the program started. A few weeks later, our floor installer noticed that the screed was still very damp — and that the underfloor heating pump was incorrectly adjusted. In his opinion (though he is not a heating engineer), this caused the entire heating-up program not to run properly. In any case, he advised us to ventilate, ventilate, ventilate. In consultation with the construction company, we ran a second heating-up program. The result: cracks everywhere at the joints of the gypsum fiber boards — most likely caused by drying.
So, be careful!

stefanc84 schrieb:
I wouldn’t agree with that...
For us, the drywall finishing was done only after the heating program, specifically a full 6 weeks after it started. A few weeks later, our floor installer noticed that the screed was still very damp – and that the underfloor heating pump was incorrectly adjusted. In his opinion (though he’s not a heating specialist) this caused the whole heating program to run improperly. Anyway, he advised us to ventilate thoroughly, ventilate thoroughly, ventilate thoroughly. In coordination with the construction company, we ran a second heating program. The result: cracks appeared everywhere at the joints of the gypsum fiberboards – presumably due to drying.
So, be careful!

Were the joints of your gypsum fiberboards taped or just skimmed?

Please embed a joint tape or mesh tape in the plaster; this will prevent any cracking.

Nordlys schrieb:
Please embed a joint tape or mesh tape as well; that way, it won’t crack.

Well, unfortunately, that wasn’t done. It’s possible that cracking wouldn’t occur then. But drying and heat definitely cause movement in the wall. Also, sanding probably only works properly once the boards are completely dry. Applying filler adds additional moisture into the house. All reasons to perhaps wait longer.