Advice for decorating over dried damp-affected-plaster

[Concussed]

We had a hole in the roof above the stairs that led to a damp patch in plaster of about 1+ metre square.
We are about to re-decorate (paint) and have been advised to cover the damaged plaster with special paint to stop chemicals leaching thru the new paint and showing the patch that was damp.

It seems a pity to buy some, especially for a small area that isn’t really visible anyway… can I apply some diluted PVA over the area instead before decorating (or any other advice)?

Thanks in advance

 

[Galena1]

Hi concussed - No you can't apply emulsion over PVA. Get a small can of spray 'Stain Block' and use that on the affected area, it won't cost much. Regards.

 

[tonygerm]

oil based undercoat should do the trick it will act as a sealer..2 even better