Wall Priming - Two Coats of White Paint

The most common case is after skimming and repairs. Fresh skim, filler and old plaster each soak up paint differently. With one coat this shows as dull and slightly shinier patches, and side light from a window makes them very visible. A second coat evens out those differences.

In new builds the walls are usually fresh plaster or plasterboard. Both are absorbent and uneven, so a single coat soaks into the surface and almost disappears. In practice the first coat on new plaster is often a "mist coat", which is emulsion thinned according to the manufacturer's instructions so that it soaks in and seals the surface. Two coats give the first continuous paint film. A coloured finish then goes on more easily and needs less paint.

If you are covering a dark colour such as blue, grey or red, a white layer in between is essential. Very strong colours may still show through after two coats, so a third coat or a paint with higher opacity may be needed.

Landlords and sellers often choose white before a flat is let or sold. It looks neutral, makes rooms feel larger and is easy for the next occupant to repaint.

Preparation decides most of the result. Even good paint will not hide dust, grease or unrepaired cracks.

1. Move furniture out or cover it, protect the floor and mask windows, door frames and skirting boards.
2. Clean dust, cobwebs and greasy marks off the walls and scrape away any loose old paint.
3. Fill holes and cracks, then sand the filler smooth once it is dry and dust it off.
4. Prime or seal the surface, especially new plaster, fresh skim, plasterboard and repaired areas.
5. Cut in with a brush around corners, the ceiling line, sockets and behind radiators.
6. Roll on the first coat and let it dry completely.
7. Check the wall, then fill and touch up any small defects.
8. Apply the second coat, again starting with the edges and then rolling the open areas.

Why does the ceiling come before the walls? Paint always drips or spatters a little from the ceiling, so it makes sense for those marks to land on walls that still need painting.

Most living spaces get a standard interior emulsion, usually in a matt finish. It lets the wall breathe, dries quickly and covers well. It works well in a living room, bedroom or home office.

Washable, scuff-resistant emulsion suits hallways, children's rooms and kitchens. Walls there get dirty more often and need wiping with a damp cloth now and then. This paint is less absorbent, so marks do not sink as deep into the finish.

Primer-sealer paint works as primer and first coat in one. It suits new plaster and plasterboard when you want to save a step. On a dusty, crumbly or very absorbent surface, a separate penetrating primer is usually the safer choice.

Bathrooms and rooms prone to mould are often painted with an anti-mould emulsion. The paint alone will not solve mould, though, unless you deal with the cause, which is usually damp and poor ventilation.

The quickest case is an empty room with flat, previously painted walls of normal height. These things add time and cost:

• Absorbent or new surfaces that need priming and more paint
• Lots of repairs, filling and sanding
• A dark or strongly coloured existing finish
• High ceilings, stairwells and areas that need scaffolding or a tower
• Walls with alcoves, many corners, pipes and radiators
• Furniture that stays in the room and has to be moved and covered

On larger empty areas, such as a new build, a decorator may offer spraying. It is fast and leaves no roller marks. Everything around the walls has to be masked very carefully, though, and the decorator needs experience with spray equipment. Spraying does not suit a furnished home.

You can paint an ordinary room yourself. You need a stable low stepladder or an extension pole, a medium-pile roller (for smooth walls usually roughly 12 to 18 mm), a flat brush, a roller tray or bucket grid and dust sheets. Ventilate the room while you work and while the paint dries, but avoid draughts and direct sun on wet paint.

1. Switch off the circuit breaker for the room's sockets and switches if you want to unscrew the faceplates.
2. Cover the floor and furniture and mask skirting boards, door frames and window frames.
3. Wash greasy marks, dust the walls and fill small holes.
4. Prime repaired and absorbent areas following the instructions on the tin.
5. Stir the paint thoroughly and only thin it as the manufacturer recommends.
6. Cut in a strip with the brush along corners, the ceiling line and around sockets.
7. Load the roller, roll off the excess on the grid and apply the paint in overlapping strips.
8. Finish one wall in one go, without stopping in the middle of it.
9. Let the coat dry for as long as the manufacturer states, usually a few hours.
10. Apply the second coat with the same tools and in the same way.
11. Remove the masking tape before the paint is fully dry so it does not tear the paint edge.

White paint reveals every bump and every bad stroke. These mistakes come up often in practice:

• Skipping the primer: the paint soaks in unevenly, leaves patches and does not grip as well
• Not stirring the paint: pigment settles at the bottom and coverage varies across the wall
• Paint too thick or too thin: thick paint leaves roller marks, thin paint covers poorly and runs
• Rolling over areas that have already dried: visible stripes and patchy areas appear where wet meets dry
• Second coat too soon: the roller lifts the still soft first coat
• Too little paint on the roller: stretching paint over a large area leaves thin, see-through spots

Look at the walls in daylight and again in the evening. A lamp or torch held at a low angle close to the wall shows the most.

• The paint is continuous, with no filler, patches or old colour showing through
• There are no dull and shiny patches and no roller stripes
• Corners and edges are painted the same as the open wall, with no grey borders
• There are no runs, drips or roller fibres stuck in the paint
• The line between wall and ceiling is straight and clean
• Floors, windows, door frames and switches are free of paint marks
• The room is tidy and all masking and dust sheets have been removed