The tin says one coat, yet the wall still looks patchy in afternoon sun. How many coats of paint you really need is usually two for walls and ceilings, and three or more when the surface or the colour makes the job harder.

Below are the myths behind most patchy finishes, then a surface-by-surface guide. It also helps you check what painters and decorators have promised in a quote.

Myth: one coat is enough if the tin says so

One coat claims come from tests on ideal surfaces, usually a sound wall already painted in a similar shade. Your hallway, with scuffs, filler marks and a colour change, is not an ideal surface.

A second coat does more than add cover. It evens out the sheen, so filled patches and fresh paint stop showing as dull or shiny islands. Treat two coats as the default and one as the exception.

Myth: extra coats fix a poor base

New plaster soaks up paint like blotting paper. Put two full coats straight onto it and the first one disappears into the wall, leaving a weak finish that can flake later.

The first coat on bare plaster should be a mist coat, which is emulsion thinned with water as the tin directs. Let new plaster dry fully before you start, which can take several weeks. After the mist coat, add two proper topcoats.

Myth: one thick coat beats two thin ones

Thick paint drips, dries unevenly and can crack at the edges. It also takes far longer to harden through.

Two thin coats look smoother and last longer. Most emulsions can take a second coat within a few hours, so a decorator can often finish both coats in a day once preparation is done. Read the recoat time on your tin, because oil-based gloss often needs 16 hours or more.

How many coats each surface needs

• Previously painted wall, same colour: one or two coats, depending on how worn the old paint is.
• Previously painted wall, new colour: two coats.
• Dark colour to light: stain block or primer, then two coats. Deep reds and navies often take more.
• New plaster: mist coat, then two topcoats.
• Ceiling: two coats of matt-white, and a stain block first over water marks or nicotine.
• Bare wood: primer, undercoat and topcoat, following the system printed on the tin.

Short answers to common questions

Can I skip primer if I use two coats?

Not on bare plaster, bare wood or stained surfaces. Primer seals the surface, and topcoats alone will not.

Does a darker colour need more coats?

Usually a little more care rather than more paint. Covering strong shades with a lighter one is the hard direction.

Do paint and primer in one tins replace a primer?

They help on previously painted walls, but they do not replace a mist coat on new plaster or a stain block over marks.

How do I know a third coat is needed?

Hold a torch flat against the wall in a dark room. Thin or glossy patches show up straight away.

Is a third coat wasted money?

Only if the second one already looks even. A third coat on a patchy wall costs far less than repainting the room next year.

What careful decorators do between coats

They wait for the recoat time rather than judging by touch. They sand glossy woodwork lightly between coats, and they keep a wet edge so roller marks do not dry in stripes.

Final checks happen in daylight, then again with the lights on, because the two show different flaws.

The simple rule

Plan for two coats on every wall and ceiling, add preparation coats where the surface needs them, and expect more for dramatic colour changes. Once you know how many coats of paint you really need, you can compare quotes sensibly and spot any that promise a perfect finish in one pass.