General information for DIY decorating, not a safety assessment of your home. If your home was built before 1978 (US) or you aren’t sure whether old paint contains lead, read the lead section below before you sand anything.
You’ve bought a tin of emulsion, a roller and a roll of masking tape, and the spare bedroom has to be finished by Sunday night. To paint a room properly, the order of work matters more than the quality of the brush: fill and sand first, clean second, cut in third, roll fourth, and let each coat dry before the next. This guide follows that order, with the air-quality and lead guidance from the US Environmental Protection Agency (EPA) where it affects what you do.
What it takes to paint a room properly, in order
Most of the time goes on the parts nobody photographs. For a typical 4m by 3.5m bedroom, expect a few hours of preparation, an hour or two per coat, and drying time between coats. The sequence below is standard decorating practice rather than a published standard, so where an official source says something specific it’s linked, and everything else is plain practical advice.
| Step | What you do | How you know it’s done |
|---|---|---|
| 1. Clear and cover | Move furniture out or to the middle, lay dust sheets, take off switch plates | Nothing within arm’s reach of a wall is uncovered |
| 2. Repair | Fill holes and cracks, leave to dry fully, sand level | Run your palm over the wall: no ridges or dents |
| 3. Clean | Wipe off dust and grease, let the wall dry | A damp cloth comes away clean |
| 4. Prime (where needed) | Seal patched areas, stains and bare plaster | Patches no longer look darker or glossier than the wall |
| 5. Tape and cut in | Brush a 5 to 8cm band along edges, corners and the ceiling line | Edge is straight, with no thick ridge of paint |
| 6. Roll | Work in sections of about one square metre, joining each to wet paint | No bands or dry edges when the wall is wet |
| 7. Second coat | After the drying time on the tin | Colour is even in daylight and at an angle |
| 8. Finish | Remove tape, clean tools, close the tin tightly | Room ventilated for days, not hours |
Check for lead before you sand
The EPA says that around three-quarters of US homes built before 1978 still contain some lead-based paint. Painting itself over sound paint is not the problem. Sanding and scraping are, because they create dust. The EPA page says that its Renovation, Repair and Painting rule generally doesn’t cover homeowners working on their own pre-1978 home, but it applies if you rent out all or part of the place, run a childcare business there, or buy, renovate and sell for profit. It also tells DIY owners to use lead-safe work practices anyway.
In practice that means three decisions before you pick up sandpaper:
- If the home is older than 1978 (US), assume the paint may contain lead until it’s tested.
- Leave painted surfaces that are intact alone, and clean rather than sand wherever you can.
- If the job involves heavy scraping or sanding of old paint, consider hiring a contractor certified in lead-safe work, and keep children and pregnant women out of the room.
Other countries have their own rules and dates, so check your national or local guidance. The 1978 cut-off is a US figure.
Prepare the room and the walls
Repair, then sand
Fill nail holes and hairline cracks with filler, press it slightly proud of the wall, and leave it until it’s fully hard. Filler that looks dry on top can still be damp underneath and will flash through the paint. Sand with fine paper on a block until the patch is flush, then wipe the dust off with a barely damp cloth.
A glossy or very smooth old finish needs a light scuff so new paint can grip. On a lead-risk wall, skip this and use a deglosser or a bonding primer instead.
Clean the walls
Grease and dust stop paint sticking. Kitchens and areas near light switches carry the most. Wipe with warm water and a little washing-up liquid, rinse with clean water, and give the wall time to dry before you tape.
Prime where you need to
You don’t have to prime every wall. Prime new plaster, large filled areas, water stains and strong colour changes. Spot-priming patches stops them showing as dull or shiny islands under the finish.
Choose paint and work out how much you need
Water-based (latex or acrylic) paint is the usual choice indoors. The EPA’s indoor-air page says that water-based paints will in general emit fewer chemicals and lower levels of vapour, and the EPA adds that solvents from alkyd (oil-based) paints can expose you to significantly more than latex paints. Kitchens and bathrooms usually call for a finish sold as moisture-resistant or washable, and the tin will say.
Example: the bedroom is 4m by 3.5m with a 2.4m ceiling. The walls’ perimeter is 2 x (4 + 3.5) = 15m, so the wall area is 15 x 2.4 = 36 square metres. Take off a door (about 1.6 square metres) and a window (about 1.5), leaving roughly 32.9. Two coats is about 65.8 square metres of paint. If the tin claims 12 square metres per litre, you need around 5.5 litres, so buy 6. Use the figure on your own tin, because coverage varies with the product and with how porous the wall is.
Buy all the paint for the room in one go and mix tins together in a bucket, so a slight difference between batches can’t show up as a visible join.
Cut in, then roll
Cutting in
Cutting in means painting the edges with a brush before you roll. Tape helps beginners, and pressing it down firmly with a putty knife stops paint creeping under it. Dip a third of the bristles, wipe one side on the tin, and paint a band of 5 to 8cm along the corner, ceiling line and skirting. A steady, slightly loaded brush leaves a cleaner line than a dry one pushed hard.
Rolling
Load the roller from a tray, roll off the excess on the ramp, and make a loose W about a metre wide on the wall. Then fill the W with parallel strokes, without pressing hard. Move to the next section and roll back into the wet edge of the last one. That’s the idea of keeping a wet edge: if one section dries before you join it, the overlap shows as a stripe.
Most visible mistakes in a painted room happen before the first coat goes on, in a patch that was never sanded flush.
Brush the cutting-in and roll the same wall within a few minutes of each other. Cut in a whole room before rolling and the brushed bands will dry, then look a different texture and sheen from the roller work beside them.
Air, safety and children
Most paints give off volatile organic compounds, and the EPA says most of those emissions happen while the paint dries, in the first few days. Its page on remodelling recommends ventilating from the start of the painting work until two or three days after it’s finished. A separate EPA guide for residents says to place a box fan securely in the window blowing out, and says an air conditioner shouldn’t replace a fan.
The same EPA guide to healthy indoor painting says pregnant women should avoid taking on painting projects and limit their time in freshly painted rooms, and that young children and people with breathing problems should avoid paint vapours. If someone in your household falls into those groups, paint while they’re elsewhere, and plan for them to stay out of the room for a few days. Keep a stable ladder on a flat floor and never lean to reach a spot.
Second coat, tape and clear-up
Leave the first coat for the time stated on the tin before recoating. Rushing it can drag the first layer into the second and leave a patchy surface. Check the finish in daylight and again at an angle with a torch, since light skimming across the wall shows thin spots.
Peel the tape back on itself while the second coat is still slightly tacky, so it doesn’t lift dried paint with it. If you wait until the paint has hardened fully, score along the edge with a blade first.
Close leftover paint tightly, as the EPA guide advises. Never pour it down a drain. The EPA says that many communities run household hazardous waste collections and suggests contacting your local environmental, health or solid waste agency. The nepis guide adds that latex paint and its containers can often go out with ordinary rubbish, so check your council or county rules for dried paint before binning anything.
Checklist for painting day
- Lead question answered if the home is older than 1978 (US) or the paint’s age is unknown
- Furniture removed or covered, switch plates off
- Holes and cracks filled, dry, sanded flush and dusted
- Walls cleaned and fully dry
- Patches, stains and bare areas primed
- Paint quantity worked out from room area, with spare for touch-ups
- Window open with a fan blowing out, plan for two to three days of airing
- Children, pregnant women and anyone with breathing problems elsewhere
- Cutting in and rolling done close together, keeping a wet edge
- Second coat applied after the time on the tin
- Tape removed, leftover paint sealed, local disposal rules checked
Common mistakes
Skipping the sanding of filler is the most frequent one, and every patch shows afterwards. Painting over dust or greasy marks is the second, because the new coat peels in those spots. The third is painting a big wall in one hit with an oversized loaded roller and then going back over half-dry areas, which drags the film into ridges.
The takeaway
To paint a room properly, spend the first half of the job on the wall: repairs, sanding, cleaning and priming. Check the lead question for older homes, ventilate from the first brushstroke to two or three days after the last, and cut in and roll close together so every coat joins a wet edge.
