White emulsion paint turning yellow

[forthgirl19]

I painted my daughters bedroom last summer with white paint. For the last couple of months parts of the bay window wall (right slope wall) has been turning yellow and crusty. I'm paranoid about it being damp. It is a plasterboard wall that was battoned onto the existing wall. As the cottage is over 100 yrs old the wall was not a good surface for plastering. Is it damp or a leak or does this happen with white paint.
Thanks

It is the right hand side of the bay window.

 

[misterhelpful]

Emulsion paints don't usually yellow and certainly not to that extent. If it is an oil based paint then it is possible, but my guess would be that there is some sort of moisture issue.

The crustiness could be efflorescence but doesn't usually come through plasterboard unless there is a lot of damp behind it.

If you could possibly post a pic it would help a lot in identifying the problem.

 

[TheDec]

forthgirl,

The first thing you need to do is calm down and stop worrying, there are many reasons why water based paints can offer this type of problem. You say that the wall is plasterboard, firstly scrape off the paint to determine if your problem is caused by the ingress of moisture the boarding will appear damp to the touch soft in texture and stained in appearance. Determine this and post back for more advice, and stop worrying

Dec

 

[joe-90]

It's damp. No need to scrape it.

 

[Nige F]

I'm paranoid about it being damp. .

Ever thought of a job as a counsellor , Joe

 

[JohnD]

does she smoke, or light candles?

 

[TheDec]

Judging where this discolouration has appeared it could also be just be a problem with condensation, if the windows are subject to this moisture could have penatrated the boards thus causing the discoloration. Also as Mr H pointed out salts within the boards could have activated thus causing the early stages of efflorescence.

If this is so this problem would be easily cured with an increase in ventilation and the application of the correct primer to the plasterboards.

Dec