How Long Does Plaster Take to Dry?

You’ve just had a room plastered, the walls look lovely and smooth, and you want to get the paint on. It’s one of the most common questions we get asked: how long do I need to wait? The honest answer is “until it’s properly dry”, and that depends on a few things. Here’s a plain guide to what affects drying, how to tell when your plaster is ready, and how to paint it so the finish lasts.

Why you shouldn’t rush it

Fresh plaster holds a lot of water. If you paint over it too soon, that moisture gets trapped behind the paint. The usual results are paint that peels or flakes, patches that blister, and dark or blotchy areas where the wall is still drying underneath. Some paints, especially vinyl and other wipeable paints, form a skin that stops the plaster drying out at all. Waiting a little longer at the start saves you repainting the room later.

What affects how long plaster takes to dry

There’s no single number that fits every job. These are the things that make the biggest difference:

• How thick the plaster is. A thin finish coat over plasterboard or an existing wall dries much faster than a full re-plaster with a backing coat and a finish coat.
• What’s underneath. A finish coat on new plasterboard usually dries quicker than plaster on brick or block, which can hold moisture for longer.
• The weather and time of year. Plaster dries more slowly in cold, damp weather, so a room done in winter will often take longer than one done in summer.
• Ventilation. Air moving through the room carries the moisture away. A closed-up room dries slowly.
• Heating. Gentle background heat helps, but blasting heaters or a dehumidifier right next to fresh plaster can make it dry too fast and crack.

As a rough guide, a thin finish coat in a warm, well-ventilated room is often dry within a few days to about a week. Thicker backing plaster, a whole house done at once, or work done in cold weather can take a good deal longer, sometimes several weeks. Your plasterer should be able to give you an idea for your particular job.

How to tell when plaster is dry

Forget the calendar and look at the wall. Fresh plaster starts off a dark brown or pinkish-brown colour. As it dries, it turns a pale, even light pink all over.

• Dry: an even, pale pink colour across the whole wall, with no darker patches.
• Not dry yet: darker patches, often in corners, behind radiators, around window reveals or low down near the skirting.
• Feel: damp plaster can feel cold to the touch compared with the rest of the wall.

If there are still dark patches, give it more time. Those areas are usually the last to dry, and they’re the ones most likely to cause trouble if you paint over them.

Helping it dry without causing problems

1. Open a window or two when you can, and keep internal doors open so air moves around.
2. Keep the house at a normal, steady temperature. Gentle background heating is fine.
3. Don’t point a fan heater or hairdryer at the wall, and don’t push a radiator up to full blast right away. Drying too fast can lead to fine cracks.
4. Avoid drying washing in the room or running a bath or shower with the door open if you can help it, as it puts moisture back into the air.

The mist coat: the first coat on new plaster

Once the plaster is dry, the first coat of paint is usually a “mist coat”. New plaster is very absorbent, and ordinary emulsion straight on will often soak in unevenly and then peel. A mist coat is a watered-down coat of plain, matt contract emulsion that soaks into the surface and seals it, giving the next coats something to grip.

1. Use a cheap, plain, matt emulsion. Not vinyl or wipe-clean.
2. Thin it with water as the tin says. Some paints are made for new plaster and need no water.
3. Roll it on. It will look patchy. That is fine.
4. Let it dry, then put on your top coats as normal.

Mistakes to avoid

• Painting too soon. The most common one. Wait for even, pale pink all over.
• Using vinyl or wipe-clean paint first. It traps the damp. Mist coat first.
• Blasting the heat. Fan heaters, hair dryers or radiators on full right next to the wall can crack the plaster.
• Sanding hard. Good plaster should not need it. Heavy sanding can scuff the face and leave dust that stops paint sticking.
• Papering or tiling too soon. Wallpaper and tiles need a dry wall too (see below).

Drying plaster in winter

Plastering goes on all year, but winter needs a bit more care. The air is cold and damp, so plaster takes longer to dry.

• Keep the heating on low and steady, day and night if you can, rather than on full for short bursts.
• Open a window for a short time each day to let damp air out, then close it.
• Keep inside doors open so air moves through the house.
• A dehumidifier can help, but keep it away from the wall and do not start it the minute the plasterer leaves.
• Expect it to take longer, and plan your painting and new flooring with that in mind.

Tiling, wallpaper and other finishes

The same rule applies if you’re tiling or papering: the plaster needs to be fully dry first. For wallpaper, a coat of size or a thinned mist coat on the new plaster helps the paste grip and makes it easier to strip in future. For tiling, check the tile adhesive maker’s advice for new plaster, because some need a primer first.

Quick checklist

• Wait until the whole wall is an even, pale pink colour.
• Keep the room ventilated with gentle, steady heat.
• Use a thinned matt emulsion mist coat first.
• Don’t use vinyl or wipeable paint on new plaster until it has been sealed.
• If dark patches don’t clear after a few weeks, ask someone to check for damp.

Need a room plastered?

RCR Connections Ltd is Birmingham based, covering the whole of the Midlands, and our team has 62 years of combined experience. When we finish a room we always give you drying and mist coat advice for that job, so you know when it’s safe to decorate. See our plastering and rendering services, or local pages for plastering in Shirley, plastering in Solihull and plastering in Birmingham.

Free plastering quote: WhatsApp me on 07453 614095 or message the page. You can also use our contact page. We work Mon-Fri 7am-5pm and Sat 7am-1pm.