How to Prepare Woodwork for Painting: Skirting, Doors and Frames
A practical guide to preparing skirting boards, doors and window frames for paint, from cleaning and keying to filling, caulking, priming and undercoat.
Woodwork takes more punishment than walls and shows faults more readily, particularly in a shiny finish. Doors are handled, skirting boards are kicked and window frames cope with condensation. A good paint job depends on preparation more than on the paint itself.
Assess the condition
Look closely at each surface:
- Sound and glossy. Needs cleaning and light sanding to key.
- Chipped or flaking. Needs scraping back to a firm edge.
- Bare wood. Needs priming.
- Rotten or soft. Needs repair or replacement before painting. A screwdriver tip pushed in will sink easily into rot.
- Previous heavy build-up. May need stripping if the detail is lost.
If the property is older, be mindful of old paint layers. See lead paint in older homes before dry sanding.
Step 1: Clean
Grease, dirt and polish prevent paint from sticking. Wash with warm water and a degreaser or sugar soap solution, following the product instructions, then rinse and let dry. Pay particular attention to door edges near handles and the lower parts of skirting boards.
Step 2: Scrape and repair
- Scrape away loose or blistered paint.
- Sand the edges of remaining paint to feather them.
- Fill dents, nail holes and splits with wood filler.
- Allow filler to dry fully, then sand flush.
- Fill gaps between skirting and wall, and around architraves, with decorator's caulk, smoothing with a damp finger or tool.
Step 3: Key the surface
Glossy paint needs roughening so the new coat can grip. Use a medium to fine sandpaper or a sanding sponge, working with the grain where possible. You are aiming for a dull, even surface, not to remove all the paint. Wipe away dust with a tack cloth or a barely damp lint-free cloth.
Step 4: Prime and undercoat
- Bare wood needs a wood primer.
- Knots in softwood can bleed resin, so treat with a knotting solution.
- Filled patches benefit from spot priming.
- Colour change from dark to light often needs an undercoat.
Check the tins for compatibility. Water-based and oil-based systems are not always interchangeable.
Step 5: Masking and protection
Mask walls, floors and glass where needed. Many decorators prefer to cut in by eye, but tape helps beginners. Remove tape while the paint is slightly tacky to avoid pulling off the edge. See protecting floors and furniture.
Doors and windows specifics
Doors
Remove handles and latches if possible. Take doors off hinges for the best finish, or at least paint in a logical order: panels, then horizontal rails, then vertical stiles. Do not forget top and bottom edges, which help prevent moisture ingress.
Windows
Open sashes slightly to avoid sealing them shut. Check for failed putty, rot or gaps. Frames exposed to condensation can develop mould, which should be cleaned and treated first.
Which finish?
Water-based satin and eggshell finishes are popular because they dry quickly and have less yellowing. Gloss is highly durable but shows imperfections. See the best finish for skirting boards and doors.
Common mistakes
- Painting over dirt or polish
- Skipping sanding on gloss
- Applying thick coats that sag
- Painting over rotten wood
- Not allowing for drying times, which are covered in paint drying and recoating times
How much preparation does each condition need?
| Condition | What to do | Time estimate per door |
|---|---|---|
| Sound, satin or eggshell | Clean, light key, spot prime repairs | Under an hour |
| Glossy, in good order | Clean, sand to dull, prime bare patches | An hour or so |
| Chipped, flaking | Scrape, feather, fill, sand, prime | Half a day |
| Heavy build-up | Consider stripping and re-priming | Longer, often a day |
| Bare or new wood | Knot, prime, undercoat | Half a day plus drying |
These are rough planning figures, since doors with panels and mouldings take longer than flat doors.
Fillers and caulk: choosing well
- Wood filler suits dents, splits and nail holes in bare or primed wood.
- Flexible decorator's caulk suits joints between skirting and wall, and around frames, where small movement would crack hard filler.
- Exterior filler is needed on external frames, where moisture and temperature changes are greater.
Prime filled areas before the topcoat, otherwise they can show as dull patches through the finish.
Special surfaces
Previously stained or varnished woodwork
Clean and sand through the sheen, then use a primer that is suitable for the old finish. Some stains can bleed through, so a stain-blocking primer may be needed on tannin-rich woods.
Radiators and metalwork
Let radiators cool, clean and lightly key them, then use a primer and paint made for metal and heat. Rust should be removed back to a sound surface.
Pre-primed MDF
Often only needs a light sand and a thin coat of undercoat. Seal cut edges, because they absorb paint unevenly.
Do's and don'ts
- Do work in good light, so you see sags while the paint is still wet.
- Do start on the least visible part, so your technique improves before you reach the focal areas.
- Do not paint over dust. A light wipe after sanding is worth the minute it takes.
- Do not use thick coats to speed things up. Two thin coats look and wear better than one heavy one.
Frequently asked questions
Do I need to sand every time I repaint woodwork?
If the surface is glossy or rough, yes, at least a light key. A sound, matt or satin finish may need less, but cleaning is always needed.
Can I paint over varnish?
Yes, if cleaned, keyed and primed with a suitable product. Varnish is slippery, so skipping prep leads to peeling.
Is it worth taking doors off their hinges?
Often, yes. It makes it easier to paint all sides and edges cleanly, though it takes extra time.
Do I need to remove all the old paint?
No, only if it is flaking, very thick or hiding detail. Sound paint can be cleaned, keyed and painted over. Stripping is usually reserved for badly damaged or heavily built-up woodwork.