What to consider before painting

How much paint do I need?

To calculate how much paint you need, there are a few simple things you need to know:

  • Wall/ceiling area (height x width of the wall).
  • Coverage rate of the paint you are using (on the can).
  • How many coats you need (on the can).

For the wall/ceiling area, simply measure the width and height, and multiply them together. E.g. for a wall of 3m x 2.4m, the area is 7.2m2 (3 x 2.4).

Then, check the coverage rate on the paint can. This will vary from product to product.

The coverage rate is per coat, e.g. 12m2/L. So one litre would be sufficient for one coat of a 7.2m2 wall.

Finally, how many coats do you need? This information will also appear on the can label. For the example product and wall mentioned above, if it is a 2 coat product you would need 2L for the project (2 coats x 7.2m2 = 14.4m2. If coverage is 12m2/L you would need 2L).


Protect unpainted surfaces and furniture by removing all furniture from the room.

Lay down a proper drop sheet to protect your floors. Try not to use old sheets as paint will often soak through. Mask skirting boards, window trim and electrical switches with painter’s tape.

If painting the ceiling, tape around light fittings and any vents.

Surface with Mould

  • If your walls or ceiling have mould, you will need to remove the mould with Selleys® Rapid Mould Killer™.
  • Scrub with a scouring pad and bleach solution (1 part bleach to 3 parts water).
  • Leave solution on the surface for 15 minutes then wash with clean water and wipe dry.
  • Several applications may be necessary to remove stubborn mould blooms.
  • Once the mould has been removed and the surface is clean, dry and free from dust, oils and grease, you can paint without an undercoat.

Do I need an undercoat?

Already painted in good condition

If the surface is already painted and in good condition, with no stains or mould, you shouldn’t need an undercoat. Ensure the surface is clean, dry and free from dust, oils and grease before you get going.

Unpainted walls in good condition

If you are painting bare, unpainted walls or ceiling, apply one coat of Dulux 1 Step Acrylic Sealer Undercoat over the entire surface before you get on with it.


If there are stains on your walls or ceiling, you will need to use a specialist stain blocker to prevent the stains migrating through your topcoat and appearing in your new paint job. The Dulux PRECISION range of specialty stain blockers will have a product to suit your stain problem.

Cracks or holes

  • Patch any cracks and holes with a suitable filler or sealant, such as Selleys® Spakfilla®.
  • Lightly sand down the surface to a smooth level then dust off.
  • Apply one coat of Dulux 1 Step Acrylic Sealer Undercoat over the repairs.