Rubbing Down and Surface Preparation Before Painting: A Decorator's Guide
The complete guide to rubbing down painted surfaces before repainting. Correct abrasives by substrate, wet vs dry sanding, feathering edges, and de-nibing between coats.
Why Rubbing Down Is the Job Nobody Photographs
In painting and decorating, the work that gets photographed is the finished colour on the wall. The work that determines whether that colour looks good in six months or six years happens before the tin is opened. Rubbing down — the abrasion of existing or previous paint coats to create a mechanical key, remove surface defects, and improve adhesion — is one of the most important and most routinely skimped stages in decoration.
This guide covers the correct approach by substrate and situation, the abrasives to choose, and the techniques that separate preparation done properly from preparation that merely looks done.
Choosing the Right Abrasive
The grit rating of sandpaper describes the number of abrasive particles per square inch: lower numbers are coarser, higher numbers are finer. For painting preparation purposes, the relevant range runs from about 60 grit (very coarse, used for stripping and heavy flatting back) to 400 grit (very fine, used for de-nibing between coats).
60–80 grit: Stripping back heavily built-up paint on woodwork, levelling rough filler after application. Not a preparation abrasive for final coats — it leaves scratches that show through topcoats.
100–120 grit: General flatting back of existing painted woodwork before repainting. Removes the gloss, scuffs the surface to provide mechanical key, and levels minor surface irregularities. The right grit for most woodwork preparation.
150–180 grit: Intermediate sanding of walls, flatting back new filler before priming, and first sanding of new plaster. Also appropriate for the first sand between coats on woodwork.
240–320 grit: Fine sanding between coats on woodwork, particularly before the final coat on high-visibility surfaces such as architraves, door frames, and skirting boards.
400 grit (wet and dry): De-nibing — the removal of particles of dust, grit, or dry spray trapped in a semi-dry coat. Used dry on paint that has been allowed to fully harden.
For walls, foam sanding blocks are preferable to flat sheet abrasive for flat surfaces, and sanding poles with flexible pads work well on large areas. For woodwork profiles — mouldings, glazing bars, shaped architraves — use a sanding sponge or abrasive sheet folded around a flexible pad to follow the profile.
Wet vs Dry Sanding
Dry sanding is the default approach for most rubbing down of previously painted surfaces. It is fast, generates a useful dust that confirms you're working effectively, and is appropriate on fully dry and hardened coats.
Wet sanding — using wet-and-dry abrasive paper with water or white spirit as a lubricant — is used in specific situations:
Between coats of oil-based gloss or eggshell on fine woodwork. The lubricant prevents the abrasive from clogging, produces a finer scratch pattern, and extends the life of the paper. The result is a smoother surface between coats, which translates to a cleaner final finish on painted door panels and joinery.
Where dust is a problem. In occupied properties or rooms with sensitive finishes nearby, wet sanding confines the dust to a paste rather than allowing it to circulate. It is slower, but it is far cleaner.
Flatting back high-gloss coats. Dry sanding a hard high-gloss coat generates heat from friction, which can smear the paint film rather than abrade it. A few drops of water on a 400-grit wet-and-dry sheet prevents heat build-up and produces a more even scratch.
Feathering Edges
When a previous paint coat has chipped, flaked, or been partially stripped, the edge where sound paint meets bare substrate creates a visible step. If this step is painted over without treatment, it shows through the new coat — sometimes only just, but enough to be noticed in raking light.
The correct solution is feathering: the gradual reduction of the step by sanding progressively towards the bare area. Working with 100–120 grit on a flat block, sand at a shallow angle across the edge until the transition from the sound coat to the bare substrate becomes a gentle slope rather than a cliff. Test by running a fingernail across the junction — if you can feel a step, there is still work to do.
On wide areas of stripped or flaking paint on exterior woodwork, feathering can require significant effort and sometimes a flexible stopper or fine surface filler applied over the feathered edge to create a smooth transition. Do not rush this stage: a visible edge through a new coat of gloss on a front door or window reveals preparation that was inadequate.
De-Nibing Between Coats
De-nibing is the removal of surface contamination — dust particles, insect debris, dried spray particles, brush hairs — that have settled into a coat of paint before it fully dried and hardened. On walls, these are mostly invisible. On woodwork, particularly on high-gloss finishes, they are clearly visible as raised points or craters under any light.
The correct process: allow the coat to harden fully (not just dry) — for water-based products, typically four hours; for oil-based, overnight. Then lightly pass a 320–400 grit abrasive sheet over the surface using minimal pressure. You are not sanding the coat off; you are reducing the raised points to the level of the surrounding film. Remove all dust with a dry cloth or tack cloth, then apply the subsequent coat.
On large flat areas of woodwork — flush doors, panel faces — a sanding sponge in 320 grit used with light, consistent pressure in the direction of the grain produces a reliably flat base for the next coat.
Surface Assessment Before You Start
No amount of careful rubbing down compensates for a surface that isn't ready to receive paint. Before sanding, carry out a simple assessment: does any existing paint lift when you press a piece of tape to the surface and pull it off firmly? If so, the existing coat has lost adhesion, and you need to identify the cause — moisture, contamination, or an incompatible primer — before proceeding. Rubbing down and repainting over an adhesion-failed substrate simply moves the failure one coat out.
Correct preparation is invisible in the final result. Incorrect preparation eventually becomes visible in every result. If you'd like advice on specification or preparation for a specific project, contact us or use our free quote form.