Why there is no fixed date
It is the question nearly everyone asks once the plasterer has packed up: when can we paint? The honest answer is that it depends, and anyone who gives you a fixed date before seeing the wall and the room is guessing. Fresh plaster holds a lot of water. That water has to leave the wall before paint goes on, and how fast it leaves depends on several things working together.
A thin skim over a sound, dry wall behaves very differently from a full replaster on brickwork. A warm, airy flat in summer dries differently from a cold back bedroom in January with the windows shut. So rather than a number, it is more useful to understand what slows drying down and what helps it along.
What affects drying time
Thickness comes first. A skim coat is only a few millimetres, so there is less water to lose. A backing coat and finish on bare masonry is much thicker and can take a good deal longer. Patches where deep holes were filled may lag behind the rest of the wall.
The background matters too. Plasterboard takes up little moisture itself. Brick and older solid walls can hold water from the new coat and from the building, and in older terraces and conversions around Norwood, Streatham and Croydon you can find a mix of backgrounds in a single room.
Then there is the room. Temperature, humidity and airflow all play a part. Gentle, steady ventilation helps. A sealed room with washing drying in it does not. Winter usually means slower drying and summer usually means quicker, but neither is a rule you can plan around with certainty.
Why a pale colour alone is not proof
New plaster usually starts dark and lightens to a pale, even pink as it dries. That change is a helpful sign, but it is not a guarantee. A wall can look pale on the surface while the background behind it is still giving up moisture, especially on thicker work or solid walls. Dark patches that hang on after the rest has lightened are worth a closer look, as they can point to a thicker area or to a damp problem.
Luc checks by eye and by touch across the whole surface, paying attention to corners, window reveals and the bottom of walls, where drying is often slowest. If there is doubt, it is better to wait a little longer than to trap moisture under paint.
Damp needs fixing first
If a wall was replastered because of a leak, penetrating damp or condensation, the cause needs sorting before you think about paint. New plaster over an active damp problem will not dry properly, and paint over it is likely to bubble, stain or flake. That might mean a roofer, a plumber or a damp specialist doing their part first. A plasterer can tell you when something looks wrong, but should not be guessing the cause from the outside.
Do not force it
It is tempting to turn the heating right up, point a fan heater at the wall or run a dehumidifier flat out to hurry things along. Forced or uneven heat can dry the surface faster than the plaster behind it, which risks fine cracking and poor adhesion later. Steady background warmth and an open window, where it is safe and secure, is usually the better approach.
Mist coats and primers
Once the plaster is dry, the first coat matters. Bare plaster is very absorbent, so it needs a first coat that soaks in and bonds rather than sitting on top. You will hear plenty of advice about watering down emulsion for a mist coat. Some paints are designed to be thinned for this and some are not, and some sit on the surface and can peel. There is no single dilution that suits every product.
The safest approach is to follow what the paint manufacturer says for use on new plaster, and to check any guidance from the plaster manufacturer too. There are also primers and paints made specifically for new plaster. Luc will tell you what he plans to use and why.
When one person does both trades
If Luc has plastered the room, he can come back, check the walls and decorate when they are ready. That is one of the main reasons for booking one person for both jobs: nobody is rushing the paint to fit someone else’s diary. If you want to talk your own walls through, ring 07424 459772 or email a few photos and your postcode.