Ask any professional decorator what separates a finish that lasts from one that fails, and the answer is the same: preparation. It is the stage most people underestimate and most rushed jobs skip. Paint applied over an unstable, unfilled, or unsealed surface will flake, flash, or show every defect the moment the light catches it. This guide walks through wall preparation the way a professional approaches it.
Step 1: Clear and Protect the Room
Move furniture to the centre of the room or out entirely, remove pictures, curtains, and fittings, and cover floors with dust sheets. Loosen socket and switch faceplates slightly so you can cut in behind them rather than around them. Good masking at this stage saves hours of cleanup later.
Step 2: Wash the Walls
Walls collect grease, nicotine, aerosol residue, and general grime — all of which stop paint bonding. Wash with a sugar soap solution, working from the bottom up to avoid streaking, then rinse with clean water and allow to dry fully. Kitchens and areas around radiators need particular attention.
Step 3: Deal with Existing Defects
Flaking or Peeling Paint
Scrape back all loose paint to a firm edge, then feather-sand the boundary so the edge does not telegraph through the new coat. If large areas are unstable, a stabilising solution may be needed before anything else goes on.
Cracks and Holes
Rake out cracks to remove loose material, then fill with a flexible filler for hairline cracks or a two-coat fill for deeper damage. Overfill slightly, allow to dry fully, then sand flush. Large holes or blown plaster are a repair job, not a filling job — painting over failed plaster only hides the problem temporarily.
Stains and Marks
Water stains, ink, and smoke marks will bleed through emulsion no matter how many coats you apply. Seal them first with a dedicated stain-block primer. If a water stain is recent, find and fix the leak before decorating — never paint over a live moisture problem.
Step 4: Sand for a Key
Lightly sand the whole wall with fine-grade paper to remove nibs and give the surface a key for the new paint. Silk and sheen finishes especially need abrading before repainting, or the new coat can slide and drag. Vacuum and wipe down with a damp cloth afterwards — dust left on the wall ends up in the finish.
Step 5: Prime Where Needed
- Bare or new plaster: a mist coat (watered-down emulsion) or dedicated plaster sealer, otherwise the wall drinks the paint unevenly
- Filled areas: spot-prime every filled patch to prevent flashing — dull spots where the filler absorbs the paint differently
- Dark-to-light colour changes: a high-opacity primer or additional base coats save you from applying four or five top coats
Step 6: Caulk the Junctions
Run decorator's caulk along the junctions between walls and ceilings, skirting boards, and architraves, smoothing with a wet finger. Crisp, caulked lines are one of the clearest tells of a professional job. Allow caulk to cure fully before painting over it.
When Preparation Reveals a Bigger Problem
Preparation often uncovers issues that painting cannot fix: blown plaster, damp patches, rotten window boards, or damaged skirting. These need to be repaired first — which is why a decorating company that can co-ordinate carpentry and other repairs under one roof avoids the delays of juggling separate trades.
If you would rather have the preparation and painting done properly by professionals, see our painting and decorating service — preparation is included in every quote, across Thurrock, Essex, London, and Kent.
Need Help With Your Property?
Multrex Maintenance provides cleaning, maintenance, and facilities management across London, Essex, and Kent.
Get a Free Quote