Newly installed plasterboard going mouldy

[d000hg]

We're having a cellar slowly converted. We pulled down the 100-year-old plaster/lath ceiling and put up new plasterboard which has not yet been treated.

The cellar is not incredibly damp but it has very poor ventilation and I noticed the plasterboard has surface mold developing. The old ceiling didn't have this problem so I'm wondering a)whether to be concerned b)what to do?

Long-term there will be fans and dehumidifiers but right now, we haven't got that. I am considering putting a portable dehumidifier down there anyway but is the problem simply that the plasterboard is untreated and the paper contains nutrients? Could I buy some time either painting it, or applying PVA, or just mold preventative, until such time as it can be skimmed and painted? As I said, the old ceiling was decades old and didn't have issues with mold or damp - it was cracked and messy but not crumbly.

 

[flameport]

Improve the ventilation.
Anything else is just covering up the problem.

 

[d000hg]

Yes I know, but that work isn't scheduled for a while - it needs wiring and so on first and this is an ongoing project. I am happy to cover up the problem to save these boards getting ruined in the interim. Something on the new board is clearly susceptible to mold that wasn't in the old ceiling. But I don't want to do something that will prevent skimming later.

 

[JP_]

maybe easier short term solution is to run an extension cable down there to power a dehumidifier? Or even an extractor with some temporary ducting running up the stairs and out somewhere?

 

[d000hg]

Would the mold definitely stop simply from it being dryer? Is the humidity or the lack of ventilation most to blame?

I'm guessing I should at the very least remove the mold (damp cloth?) Maybe spray mould prevention spray after and/or a sealer to stop moisture wicking through the paper. Like a pre-plastering mist-coat but using PVA or something?
Making sure it's clean so there's nothing for the mold to eat as well?

I might do as you suggest anyway - if I'm going to get a dehumidifier I might as well get the use out of it.

 

[JP_]

A warm and dry room won't get mouldy. But it will be hard to keep it warm and dry in this weather without ventilation - moist air from above will probably sink down into the room then condense if too cold.

Maybe put a fan heater in there to run for an hour a day to help dry things out? Obviously will need extracting. Or just the dehumidify.

I've used Cillitbang Black Mould Remover on my bathroom ceiling, that kills the stuff.

 

[d000hg]

Come to think about it, they used to have a "penny heater" tube heater in there.

A fan heater temporarily might be a nice idea as it would provide ventilation too, moving the air around.

 

[JP_]

there you go - was probably on a timer.

 

[d000hg]

I think they literally just left it on 24/7. It used to be (maybe still) is a thing people did in such spaces because a 60W heater or whatever it is is so cheap to run.
I actually don't know the benefit because I'd have thought mold would thrive in warmer conditions. Maybe it causes air currents as much as anything else?

 

[JP_]

Mould needs damp surfaces to grow - a heater should help to keep the room warm and dry (or drier). maybe a little heat is enough to ward it off. Air movement is often enough to keep walls dry - this is why condensation mould tends to grow behind furniture or in wardrobes first. Do an empty cellar shouldn't be too hard to keep dry. Ventilation is probably key though - garages don't get mouldy, but are cold and exposed to outdoor air...