By the Bouwsector België team, 97 in-house tradespeople · reviewed by Geert Jan Hendrik, director · updated
A thin skim coat dries in 3 to 5 days for a whole home, faster in summer, and we can set up heater fans. Thicker traditional plaster needs longer: according to the gypsum manufacturer Knauf, gypsum plaster can be dry enough after about four weeks under good conditions. Primer and paint only go on once the layer is completely dry.
Plaster that is properly dry before the painter arrives? Request your quote
How long should plaster dry before you can paint or wallpaper?
The drying time of plaster depends mostly on the thickness of the layer. A skim coat or thin plaster is thin and dries in days. A paint-ready layer of traditional plaster is thicker and takes weeks. The times below are guideline figures: the room itself decides whether it goes faster or slower.
Layer or step
Guideline time
Source
Skim coat or thin plaster, whole home
3 to 5 days to apply and dry
Our scheduling
Skim coat or thin plaster, in summer
Faster; we can set up heater fans
Our scheduling
Gypsum plaster, under good conditions
About 4 weeks
Knauf
Sigmafix Universal primer
Ready to paint over after about 6 hours at 23 °C and 50% humidity
Sigma product data sheet
The season matters too. Knauf points out that warm air can hold more moisture than cold air. In summer a layer therefore usually dries faster than in a cold, wet spell, even indoors.
New-build homes add one more factor: the walls themselves release construction moisture for a while. Allow for that in your schedule: new-build walls still release moisture, quite apart from the plaster.
How do you know if plaster is dry?
Look at the colour. Wet plaster is darker and patchy, while dry plaster is an even, light shade. As long as you can see dark patches or edges, there is still moisture in it.
Also feel it with the back of your hand. A cool, damp feel means the layer is not ready yet, even if the surface looks dry. Feeling dry is not the same as being dry: the inside of a thick layer dries last.
Knauf puts it briefly: gypsum plaster must be completely dry before tiles or paint go on. If in doubt, wait a few extra days. A wall painted a week later is better than a wall that starts showing marks after a few weeks.
Drying plaster: windows open or closed?
Open, as long as no dehumidifier is running. According to Knauf, the key to drying is letting the damp air leave the room, either by ventilating well or by using a construction dehumidifier. Heating can help, but without ventilation the moisture just stays in the room.
In practice, ventilating means windows and doors open, so that damp air can escape and drier air comes in.
If you do use a dehumidifier, it pulls moisture out of the air in that room. Keep the windows of that room closed then, otherwise the machine mainly dries the air coming in from outside.
Can you speed up drying with a dehumidifier or heating?
Yes, within limits. Knauf names dehumidifiers and ventilation as the main aids, with heating as a supplement. A dehumidifier is most useful when you cannot ventilate, for example in a wet spell or in a room without windows that open.
According to Knauf, a temporarily damp indoor climate does no harm, provided the plaster can dry properly afterwards. A few rainy days are therefore no problem, as long as the room can be aired again afterwards.
What drying cannot do is skip the time. A thick layer needs time to dry through to the inside as well. So plan generously rather than tightly, especially if a kitchen or cupboards are going against the wall after plastering, as with a kitchen moving to a different wall.
What goes wrong if you paint or wallpaper too early?
Painting too early usually doesn’t show straight away. Paint on a damp layer traps the moisture, and only after a few weeks can the paint peel, blister or discolour.
An extra coat of paint doesn’t fix a damp or absorbent wall either. A dry wall first gets a primer, so that the paint is absorbed evenly everywhere. So dry first, then prime after plastering, and only then paint.
Does that mean waiting for weeks? Not if you choose a thin skim coat with renovation fleece over it in a new-build home. The thin layer dries in days, and the renovation fleece bridges the small shrinkage cracks of a home that is still settling. That makes a skim coat in a new build the route without weeks of waiting.
How do we plan the drying time into your job?
At Bouwsector België, our plasterers, painters and wallpaper hangers work together in one team of 97 in-house tradespeople. So we plan the next step ourselves, and only once the layer is dry. If the weather makes drying take longer, we push the painter or wallpaper hanger back instead of starting anyway.
When you apply, tell us when a kitchen or cupboards will go against the wall and when you want to move in. The free quote you receive within 24 hours then already takes the drying time into account. At the on-site survey we discuss which layer your walls need and what that means for the schedule.
Prices exclude VAT. For renovating a home over 10 years old, 6% VAT usually applies.
According to Knauf, gypsum plaster must be completely dry before tiles or paint go on. Under good conditions that can be after about four weeks. A thin skim coat is quicker, but the rule still applies: completely dry first.
How long must primer dry before you can paint?
That depends on the product. According to the Sigmafix Universal data sheet, this primer can be painted over after about 6 hours, at 23 °C and 50% relative humidity. In a cold or damp room it takes longer.
Does it matter if it rains for a few days while the plaster dries?
According to Knauf, a temporarily damp indoor climate has no negative effect, as long as the plaster can dry properly afterwards. Make sure the room can be aired well again after the wet days.
Why does plaster dry more slowly in winter?
Cold air can hold less moisture than warm air, and in wet months ventilating is harder. The moisture then leaves the layer more slowly. Heating helps, but removing the damp air matters more.
Why does a skim coat dry faster than traditional plaster?
Because the layer is much thinner. There is less moisture in it, and that moisture has a shorter way out. That is why we count in days for a whole home with a skim coat and in weeks for thick plaster.
By the Bouwsector België team, 97 in-house tradespeople · reviewed by 
