How Long Does it Take Plaster to Dry?

This page forms part of our blog which contains a series of DIY guides for consumers and homeowners.

We recently updated our price guides for plastering and wall soundproofing and realised that many homeowners may choose to save money by doing the painting and decorating themselves.

Whether you’ve just had a wall soundproofed, patch repaired or completely replastered, we hope you’ll find our guide to plaster drying times helpful.

Wet Vs Dry Plaster Colour

The two colours below show the difference between wet and dry plaster:

Wet plaster often looks like this, although it depends on the exact mixture

Dry plaster is much lighter in colour with hints of pink

Wet plaster looks earthy with hints of brown, red or dark pink.

Dry plaster is light creamy pink.

Why You Need to Wait

If you intend to paint your newly plastered walls, it’s vital that you wait until the wall is completely dry.

Most paints will seal the surface of the wall and any moisture will be contained within the wall.

This can lead to damp patches, mould and in some cases efflorescence (salting).

Plaster Drying Time

There is no fixed drying time for plaster and the time you’ll need to wait before decorating will depend on these factors:

  • how many layers of plaster were applied
  • if there’s plasterboard backing
  • the humidity of the room
  • the time of year

For patch repairs where there’s only a thin layer of plaster, you should wait around 5-6 days.

For entire walls, plaster on plasterboard will dry quite quickly and you should wait around 10-14 days before applying a mist coat.

For a wall with two or three layers of plaster (often referred to as backing plaster), you should wait around 14-21 days.

If the property is damp, has lots of moisture in the air, or the work is carried out in the winter, you should increase the drying time by around 50%.

Radiators and Dehumidifiers

Dehumidifiers should never be used to speed up the drying time of plaster.

The drying process is actually a reaction between several chemicals that are created when you add water.

If the water is extracted too quickly from the plaster, the chemical reaction will stop prematurely and the plaster won’t harden correctly and you’ll get hairline cracks.

Radiators shouldn’t be used either unless the room is particularly cold or damp (winter) and even then care should be taken as any fresh plaster behind or close to the radiator may dry out too quickly.

The one thing you should do is to open at least one window in each room that has been plastered, this will allow any moisture to escape.

Mist Coat

A mist coat is a name given to the first layer of paint that’s applied to a new plaster wall.

For most walls, this will be a mixture of one part water and three parts emulsion. Some decorators dilute the paint to 50% water and 50% paint although you may need two mist coats at this level of dilution.

Neutral colours are recommended.

A mist coat is just another term used to describe a primer.

What Happens if You Don’t Apply a Mist Coat?

Dry plaster is extremely porous and will rapidly absorb any moisture from the paint.

To prevent the paint from peeling off, the first coat should be watered down, if it isn’t you can expect the paint to dry too quickly and it may peel off.

In a Hurry?

If you really need to get the fresh plaster painted as soon as possible and you can’t afford to wait a couple of weeks, you do have one option.

There are several paints on sale that allow the wall to breathe, these are water based and are usually labelled as “Supermatt” or “non-vinyl matt” or “contract matt”.

Television makeover and DIY shows use these paints on the same day that the plaster was laid, we suggest that at a minimum you wait at least two days before applying such paints.

Dulux has information about their version here.

Leyland has a similar product here.

The Leyland Trade Contract Matt is formulated specifically for new plaster – it is a highly breathable paint so will therefore allow the plaster to breathe whilst it is drying out. Because of the breathability the paint will mark very easily, and is very absorbent in its own right. if the plaster is still wet I would suggest thinning the 1st coat by 10% clean water and follow up with 2 full coats, then when the plaster has dried apply a thinned down solution of silk (again around 10%) followed by a further full coat. However, if the plaster has fully dried then you can apply a thinned down solution of silk straight to the plaster, followed by 2 full coats. – Leyland representitive

Kitchens and Bathrooms

Because most kitchens and bathrooms have higher levels of humidity, you should consider using an oil-based paint. For plaster walls in these rooms, we recommend sealing the wall with a PVA solution. The combination of PVA and an oil based paint will prevent mould from forming.

Under no circumstances should PVA be used on a wall that will be painted with emulsion (water-based paints).

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