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How much paint do you need?

An average 4m by 4m room with 2.4m ceilings has roughly 38m² of wall. At 12m² per litre per coat, two coats need about 6.5 litres — a 5 litre tin plus a 2.5 litre. Deduct a door and a window and you are closer to 5.9 litres.

Around 12m² per litre per coat on smooth, previously painted walls. Expect 10 on new plaster, 8 on textured surfaces and as little as 6 on bare masonry. Check the tin — deep colours and matt finishes vary.

A first coat thinned roughly 30% with water, used to seal fresh plaster so the finish coats do not sink in and flake. Skip it on new plaster and the paint will peel within a year.

More than you expect — stairwells have double-height walls. Measure the tallest drop rather than the average, and budget around 10 to 14 litres for a two-coat hall, stairs and landing in a typical terraced house.

Two to four hours for water-based emulsion, longer in a cold or humid room. Recoating too early lifts the first coat and leaves patches. Oil-based eggshell needs overnight.

A standard door takes about 0.5 litres for two coats including the frame. Skirting runs roughly 1 litre per 25 linear metres per coat. Buy 1 litre for a small room, 2.5 for a whole floor.

You can, but only if it is well stuck and not textured or vinyl. Seal any lifting seams first, then use a mist coat — wallpaper paste is absorbent. Stripping is the better job where you have the weekend.

Bare wood, metal and filler all need a primer; new plaster needs a thinned mist coat instead. Over sound existing paint in a similar shade, no primer is needed — but a tinted undercoat saves a topcoat when the colour change is dramatic.

Two over an existing similar colour. Three going light over dark, covering a strong shade, or painting fresh plaster — where a thinned mist coat comes first and does not count as a finish coat.

Yes, once there is more than one or two. A standard door is about 1.8m² and a window 1.5m². Two of each is 6.6m² — over half a litre across two coats.

A ceiling in the wall colour, or a shade lighter, makes a low room feel taller and softens the join. Bright white against a strong wall colour draws a hard line and makes the ceiling look lower.

Almost always the large tin. A 5 litre is typically 30 to 40% cheaper per litre than two 2.5s, and buying one batch avoids the slight colour drift between mixes that shows on a long wall.

Matt hides imperfect plaster and spreads furthest per litre. Eggshell has a low sheen and wipes clean — the choice for hallways and kitchens. Satin is glossier still, best kept for woodwork.

Usually yes. Ceilings take a dedicated flat matt that hides plasterboard joins and does not flash under low light. Wall emulsion on a ceiling works but shows roller lap marks more, especially in a shade darker than white.

Water-based emulsion is touch dry in an hour and ready to recoat in two to four. Oil-based eggshell wants overnight. Both cure fully over two to three weeks, which is when the finish reaches its final hardness — go gently on new woodwork until then.