Painting new plaster skim over wet cement? HELP!!

[Anonymous]

I've had a smalll, nasty extension from my breakfast room stripped back to brick. 2 layers of cement went on in 2 days (the 2nd with waterproofing additive), about 5-7cm total to correct the very uneven raw wall and the builders plan to plaster skim (pink gypsum) today...! The walls are obviously still wet, though set, and I am concerned that the cement will react with the plaster (salts, efflorescence?? I've read elsewhere in the forum). My builders have done many things wrong, according to an architect friend of mine who has also been a tradesman, and I am worried it will not dry properly behind the units.

A second question is - how soon can I paint these walls? A kitchen will be installed later this week, and I have a terrible feeling (as I didn't research this properly and the builders are 3 weeks behind schedule) I wont be able to paint the walls before it goes in and then the drying render and plaster will cause damp. I've read elsewhere eveything between painting within a few days to letting it cure for 6 months!

Thanks for any help

Helena

 

[Anonymous]

I think you're on the wrong forum!!

 

[Anonymous]

I think you may be right - my builders seem to have never heard of maintaining character in period property and I have had constant battles with them to keep features like lime plaster, original floorboards, fireplaces, etc. Getting a builder sensitive to older houses is very diffficult and all the ones I spoke to only seemed interested in renovating to todays specs. My bad luck.

Helena

 

[Anonymous]

I don't know why, but I'd got the impression that your nasty back extension was a modern addition, in which case the cement etc. is less of an issue.

 

[Anonymous]

Wven in a modern extension - why on earth are they using cement as internal plaster?

 

[Anonymous]

Approx 1 day of drying for each 1mm of wet construction before painting. So about 70 days is the necessary time, not that many builders / homeowners bother letting their plaster dry.

 

[Anonymous]

Helena - do not paint until the skim appears dry ie. the same tone as in the bag - pale pink. DO NOT use a vinyl emulsion as any residual dampness in the walls will make the stuff peel off. Use a first decoration wall paint that is more permeable. I think it is called contract emulsion but check with a local decorators merchant.
Not really a 'period property' question but you deserve some kind of answer - hope this helps. Mike.

 

[Anonymous]

I've been thinking about this. I absolutely agree - don't paint yet (despite what you see on TV makeover progs, where they seem to plaster and paint on the same day!

You can buy simple trade or contract emulsion, which is useful on bare plaster as it does suck up the paint (you can buy special paint also for bare gypsum plaster). Don't attempt anything with vinyl in until the walls are very dry - which will take a long time.

As you have no choice but to get the kitchen fitted, I'd be inclined to leave the walls behind bare, it shouldn't matter, and leave the plinths off to allow air to circulate. Kitchen units should have a small gap between them and the wall, apart from where the work surface butts up. Wall units could be a problem though.

Quite why your builders used cement render and also a waterproofer I have no idea. However, with this thickness of render plus plaster there is a huge amount of embedded water which will need to dry out, and much of that will dry inwards. Ensure your kitchen has gentle heat and adequate ventilation to allow the moisture to escape. You may also consider, if you haven't already, fitting an extractor fan. A de-humidifier may be useful in the short term, too.