How to prepare your walls for decorating


Walls almost always need some surface preparation before you can start painting. Even brand-new plaster needs sealing. You should fill any cracks and holes and make sure all surfaces are clean, smooth and dry. You can paint over emulsion-painted surfaces that are in good condition, but make certain you strip back or sand off any peeling paint.

Safety first

Always wear a dust mask while you’re sanding. With old paint, there can be an extra risk of breathing in poisonous lead dust. If you’re in any doubt, use a simple lead testing kit. If there is lead, use a specially formulated liquid sander instead. It’s also a good idea to put on some safety goggles to protect your eyes.

Also remember to wear protective goggles and masks when cutting or sawing metal. Clear away all metal dust and small pieces before starting work again.


The difference between a good and bad paint job usually depends on how carefully you prepare the surface.

No paint can properly mask grubby or uneven surfaces, so make sure you remove any dirt, grease and loose or flaking material, fill any holes and repair defects. There may even be areas that need touching up on new surfaces.

Most paints these days are perfectly ok to apply in a confined area without masks or specific ventilation requirements. However, some Gloss and specialist paints do require specific cautions to be taken so always read the paint instructions before commencing.

See our preparation methods in steps 1 to 3 below:

Step 1

Washing your surface

You should always wash a previously painted surface before painting over it. The less dirt or grease on a surface, the better your final paint job will look.

Grease, nicotine stains, children’s drawings and finger marks can all be taken off with sugar soap. Some sugar soaps come in a dissolvable powder or pre mixed liquid form.

Ensure you wear safety goggles and gloves when using sugar soap as it can irritate your skin.

Apply this with an old (clean) paintbrush or sponge, working into the surface as if you were washing the dishes. Leave the solution for a few minutes before rinsing off with clean tap water and sponge. Not only does the sugar soap clean the surface, it also provides a better surface for the paint to adhere to
In older houses, you still sometimes find distemper. This oldfashioned emulsion is often dusty or powdery to the touch, and rubs off as you wash the surface. It’s not a good idea to paint or wallpaper over it, as neither will stick. Instead, try to wash and scrape off as much as possible, and then seal the wall with a stabilising solution.

Step 2

Sanding down

Sanding creates a smooth, even foundation that massively improves your final finish. It also gives a slight roughness (known as a ‘key’) that helps primer or paint to adhere to. On stripped plaster, sanding can level out any repairs and remove stubborn traces of old wallpaper or paste.

When sanding the surface of the walls use a smaller grade/grit of paper. The grades are based around the finish you are aiming for. For example a 70 grade paper is great for quickly removing excessive debris; however it will leave a rough surface. A higher grade will give a finer finish on more delicate surfaces. For this task we would recommend a multi-purpose sandpaper such as a 70 grade.

When sanding, use a sanding block and wrap the sandpaper around it, this will ensure you cover an even surface. Sand the surface in circular motions covering all areas. If you are smoothing rough surfaces, run your hand over the area to check if it’s smooth and matches the rest of the area.

When sanding wood, try to work in the direction of the grain. Work from a lower grade sandpaper and finish with a higher one. This will create a smoother finish to paint over. Sanding wood creates a lot of dust, so make sure you wear a dust mask and eye protection, have plenty of ventilation and cover anything vulnerable with dust sheets. When you’ve finished, you’ll also need to dust down the whole sanded surface from ceiling to floor, and vacuum it thoroughly. If you don’t, you risk wood particles sticking to freshly painted surfaces.
How to prepare your walls for decorating

Step 3


You won’t need to prime a surface that’s been painted before and is in good condition – washing and light sanding are usually enough. However, if the surface is stained with nicotine you may want to consider using a specialist primer. If the wall is freshly plastered, you will need to apply a layer of primer before you paint your final coat of colour.

On a porous surface, primer stops the top coat from being absorbed, so you need fewer coats of paint to get a good coverage. On nonporous, shiny surfaces, paint often won’t bond properly – so the primer gives it something to stick to. As different surfaces need different primers, make sure you choose the right one and follow the manufacturer’s instructions. Water-based primers tend to give off less odour and are less damaging to the environment.

Choose a primer that will relate to your final colour, for example if your final coat will be a natural white, use a white primer. Similarly if your final colour will be a dark red, use a grey primer, this will help create an accurate final colour. Applying your primer layer is the same as if you were painting normal emulsion paint. Take your time applying even layer with a brush or roller. Work in sections across the surface and allow plenty of time for the paint to thoroughly dry as per the products instructions.

Priming for different surfaces

There are specific primers for different surfaces and applications so be sure to check and select the correct primer for your surface. Here are a few of the different primers available:

  • Multi-purpose primers
  • Wood primers
  • Metal primers
  • Radiator / heater primers – these are heat resistant which is very important
  • Plaster sealers – specific to newly fitted plaster board
  • Specific surface primers – these can include tile primers, radiator primers and PVC primers