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Project guide

How much paint do I need for new plaster?

Fresh plaster is thirsty. It needs a thinned mist coat to seal it before the full coats, so you need more paint than for a repaint. Here is how much, and how to do it.

Updated Based on manufacturer guidance, sources below

The short answer

For new plaster, plan on three coats: a mist coat plus two full coats. At 12 m² per litre per coat, that is 1 litre for every 4 m². A 4 x 3.5m room with 2.4m walls needs about 8.2 litres for the walls and 3.5 litres for the ceiling.

The formula

  • Wall area (m²) = perimeter x ceiling height - 1.6 m² per door - 1.5 m² per window
  • Ceiling area (m²) = length x width
  • Litres = area x 3 coats / 12 (the mist coat is thinned, so it stretches a little further)

Worked example

A freshly skimmed 4 x 3.5m room, 2.4m high, one door and one window:

  • Walls: 15 x 2.4 = 36 m², minus 3.1 m² = 32.9 m²
  • Wall paint: 32.9 x 3 / 12 = 8.2 litres
  • Ceiling: 14 m², so 14 x 3 / 12 = 3.5 litres
  • Total about 11.7 litres: a 10L tin plus a 2.5L tin of the same white, or separate tins for walls and ceiling.

Work it out for your job

Change the measurements and the quantities update straight away.

Wall area to paint
32.9 m²
Ceiling area
14 m²
Paint needed
11.7 litres (3 coats)
Walls / ceiling
8.2 L / 3.5 L
In 10L tins
2 x 10L
Or smaller tins
2 x 5L + 1 x 2.5L

Your list

  • 2Matt emulsion, 10L tins
  • 1Interior filler
  • 3Decorator's caulk, 380ml
  • 12 inch brush
  • 13 inch brush
  • 1Roller and tray set
  • 1Masking tape rolls
  • 1Sandpaper, 5 pack
  • 2Dust sheet, 3.6 x 2.7m
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Materials checklist

  • Matt emulsionA plain contract or standard matt for the mist coat, not a vinyl or wipeable finish, which can sit on the surface.
  • Clean water for thinningThin the mist coat as the paint manufacturer recommends on the tin or data sheet.
  • Roller, tray and brushesA medium-pile roller sleeve and a brush for cutting in.
  • Fine sandpaperTo take off any nibs once the plaster is dry.

You'll also need

  • Dust sheets and masking tape
  • Decorator's caulk for gaps at the skirting and frames
  • A roller extension pole for ceilings
  • Patience: let the plaster dry fully first

Step by step

  1. Let the plaster dryWait until the plaster has dried to an even pale colour all over, with no darker damp patches.
  2. Sand and dust offLightly sand any nibs and wipe away the dust.
  3. Apply the mist coatThinned emulsion, rolled on evenly so it soaks in and seals the surface.
  4. Fill and caulkOnce the mist coat shows up any small defects, fill and caulk them.
  5. Two full coatsApply two full coats of your chosen colour, letting each dry as the tin says.

Tips from the manufacturers

  • Dulux describes a thinned first coat on new plaster: it soaks in and gives the next coats something to grip.
  • Avoid vinyl or wipeable paints for the mist coat. They can form a skin on the surface instead of soaking in.
  • Use the calculator with 3 coats selected: it already allows for the mist coat.

Mistakes to avoid

  • Painting before the plaster is fully dry, which can trap moisture and cause peeling.
  • Skipping the mist coat and applying full-strength paint straight onto new plaster.
  • Buying for a normal two-coat repaint and running short.

Frequently asked questions

How long should new plaster dry before painting?

Until it has dried to an even pale colour with no darker patches. That is often several days for a skim and longer for thicker plaster, depending on the room.

How much paint for a mist coat?

Plan the mist coat as one coat at 12 m² per litre. Because it is thinned, the tin goes a little further, which gives you some spare.

Do I need two coats after a mist coat?

Usually, yes. A mist coat plus two full coats is the normal finish on new plaster.

Can I use any emulsion for a mist coat?

A plain matt emulsion is best. Vinyl and wipeable finishes can sit on the surface rather than soaking in.

Sources

Quantities are estimates for typical jobs, using the coverage figures above. Products vary, so check the data sheet for the product you buy, and talk to a professional for structural, electrical or gas work. SmartBuild is independent and not affiliated with any of the manufacturers listed.

How much paint do I need for a room?To work out how much paint you need for a room, measure the walls, take off doors and windows, multiply by the number of coats and divide by 12. Here is the rule, a worked example and a calculator that does it for you. How much plaster do I need to skim a wall or room?A finish skim is about 2mm thick. British Gypsum says a 25kg bag of Multi-Finish covers about 10 m² at that thickness. How much plasterboard do I need for a ceiling?Replacing an old lath and plaster or cracked ceiling starts with the area. Multiply the length by the width, divide by the sheet size and add a little for cuts, then work out the screws and the skim.

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