Ask any professional decorator and they will tell you the same thing: the finish is won or lost before the first coat of paint goes on. Good preparation is around 70 per cent of the job, and it is the part most DIY painters rush. Here is how we prepare walls on jobs across Wallington and the surrounding areas, step by step.
Before you touch a filler knife, look at the walls in daylight and again with a lamp held at an angle to the surface. Raking light shows up dents, old filler patches, hairline cracks and roller texture that overhead light hides. Mark every defect with a pencil so nothing gets missed once you start work.
Walls collect more grime than people expect, especially in kitchens, hallways and anywhere near a radiator. Wash them down with sugar soap diluted in warm water, working from the bottom up to avoid streaks, then rinse with clean water and let them dry fully. Paint will not bond properly to grease or nicotine staining, and in older Victorian and Edwardian houses common around this part of South London, decades of coal dust and distemper can sit under the surface. If a damp cloth pulls off a chalky residue, the wall may have old distemper on it, which needs sealing with a stabilising solution before anything else.
Rake out cracks slightly with the corner of a scraper before filling. It feels counterintuitive to make a crack bigger, but filler needs something to grip, and skimming over a hairline crack almost guarantees it reappears within months. For cracks along plasterboard joints or where walls meet ceilings, use a flexible caulk or jointing compound rather than rigid filler, as these areas move with the seasons.
Fill deep holes in two or three passes rather than one thick application, because filler shrinks as it dries. Leave each layer slightly proud, then sand back flush once fully hard, usually two to four hours for standard filler and longer in cold or humid weather. Run your hand flat over each repair; your fingertips will find ridges your eyes cannot.
Sand the whole wall lightly with 120 to 180 grit paper, not just the repairs. This keys up old sheen paint so the new coat grips, and it levels any raised edges. A pole sander makes short work of full walls and saves your shoulders. Afterwards, vacuum the walls and skirting, then wipe with a barely damp cloth, since dust left behind ends up textured into your paint.
Stains need treating, not just covering. Water marks, felt-tip, and tannin from old timber will bleed straight through standard emulsion, sometimes even through three coats. Use a dedicated stain-blocking primer on these areas first. If you find soft, crumbling plaster or recurring damp patches, stop and find the cause before decorating, because paint over unresolved damp fails quickly and can hide a problem that gets more expensive the longer it is left. In our experience locally, blocked gutters and bridged damp courses are frequent culprits.
Bare plaster and filled patches soak up paint at a different rate to the surrounding wall, which shows as dull patches called flashing. Prime fresh plaster with a mist coat, which is emulsion thinned with roughly 20 to 30 per cent water, and spot-prime every filled repair. Previously painted walls in sound condition usually do not need a full prime, just those spot repairs.
Timing matters too. Newly plastered walls need to dry out fully before painting, typically around a week for a skim coat and considerably longer for full replastering, depending on the season. Painting too soon traps moisture and leads to peeling. If you are unsure whether a wall is ready, a decorator can usually tell within minutes of seeing it, and most reputable local firms, ourselves included, are happy to advise before you commit to a full redecoration.
Yes, unless the room is nearly new and spotless. Grease, dust and handling marks stop paint bonding properly, and a sugar soap wash takes under an hour for an average room. It is the cheapest insurance you can buy for a lasting finish.
For a typical bedroom in reasonable condition, allow half a day to a full day including drying time for filler. Older properties with cracked plaster or layers of old paint can take two days or more, and that is normal rather than a sign anything is wrong.
Sometimes, if the paper is firmly stuck, smooth and not vinyl coated, but it is a compromise. Seams often show through paint and moisture from emulsion can lift loose edges, so stripping back to plaster gives a far more reliable result on older walls.