Stripping Old Oil Paintwork

Not always. It depends on the condition of the paint. If the oil paint is firm, sound and not lifting anywhere, it is often enough to sand it thoroughly, degrease it and apply an adhesion primer as the manufacturer recommends. But if the coating cracks, blisters, flakes off under a fingernail or sits in several layers, any new paint will sooner or later peel away along with the old. In that case the coating has to be stripped back to the plaster.

How can you tell it is oil paint? It is glossy or semi-gloss and hard. Water runs off it, and when you tap it, it feels like a thin shell. A simple test helps here. Rub a small spot with a cloth dampened with methylated spirits. Water-based paint usually starts to smear, while oil paint stays unchanged.

Paint in older properties can contain lead. If you live in an older building and are not sure, have the paint tested before you start and never dry-sand it. In a block of flats, contact the building management or owners' association before doing any work in shared areas such as hallways or stairwells.

The method depends on the surface (plaster, concrete, plasterboard), the number of layers and the size of the area. In practice, methods are often combined.

Hand scraping

This uses a scraper, a steel filling knife and a wire brush. It suits smaller areas and places where the paint is already coming away by itself. You have good control, and if you work carefully you will not damage the plaster. It is hard work, though, and slow on large walls. Today it is mostly used for detail work around door frames, in corners and behind radiators.

Machine sanding

An orbital or random orbit sander with coarse paper is used, and for larger areas a long-reach wall sander, often called a giraffe. Sanding is quick and roughens the surface at the same time, so the next coat has something to grip. It works well on flat, sound surfaces. It creates a lot of fine dust, so the sander should always have dust extraction and you should always wear a respirator. Press too hard and you can easily sand through softer plaster.

Chemical stripper

A gel or liquid stripper is brushed on and left to work for as long as the manufacturer says, usually somewhere between a quarter of an hour and an hour. The softened paint is then pulled off with a scraper. Stripper helps with thick, firmly bonded layers that would otherwise take days to scrape. You need good ventilation, gloves and goggles, and the residue must be washed off thoroughly.

A combination

With multi-layer coatings, the paint is often loosened with stripper first, scraped off, and the remains are then sanded. The result is a clean, slightly rough surface ready for the next steps.

The effort involved, and so the cost, depends mainly on:

• Number of layers: every extra layer means another round of scraping or stripper
• Adhesion: paint that is already peeling comes off quickly, while hard, well-bonded paint resists
• Shape of the area: a flat wall goes quickly, but a small bathroom with pipes, corners and door frames takes much longer
• Condition of the plaster: if it crumbles under the paint, filling or skimming has to be added
• Method chosen: stripper means more material and protection, sanding means equipment and dust extraction
• Protection and cleaning up: an occupied, furnished home takes more preparation than an empty room

You can handle a small area yourself if you are patient and have the right protective gear. If you suspect lead, or the area is large, it makes more sense to call a decorator.

1. Move out or cover the furniture, protect the floor with plastic sheeting and tape the edges.
2. Switch off the circuit for sockets and switches on that wall and mask them with tape.
3. Put on gloves, safety goggles and a respirator.
4. Test a small area to see how the paint reacts to the scraper and to the stripper.
5. Scrape off loose paint, holding the scraper at a shallow angle so you do not gouge the plaster.
6. Brush stripper onto the firm layers, leave it as long as the instructions say and scrape off the softened paint.
7. Sand off the remains with an extracted sander, and do corners and details by hand.
8. Wash the wall with water and a degreaser and rinse off any stripper residue.
9. Let the wall dry completely, usually for at least a day.
10. Apply a penetrating primer, and once it is dry, fill cracks and holes.
11. Sand the filler with fine paper (roughly 120 to 180 grit), vacuum the wall and wipe it with a damp cloth.

After that you can apply a white base coat and then the finish colour, usually in two coats. A wipeable paint suits kitchens and hallways, and standard emulsion works for ordinary rooms.

• Painting over glossy paint that has not been degreased. The new paint looks fine for a few weeks, then starts to peel off in strips.
• Leaving stripper residue on the wall. It can cause stains, a change in colour or poor adhesion of the following coats.
• Sanding without dust extraction. The dust spreads through the whole home and is harmful to breathe, especially from old paint.
• Skipping the primer. Bare plaster and filled areas absorb paint differently, and patches show through after painting.
• Rushing. Painting a damp wall or cutting the stripper's working time short usually leads to repairs later.
• Leaving islands of old paint. The edges between old paint and bare plaster show through the new coat unless they are feathered out.

Before painting, look over the wall in raking light, for example with a torch held flat against the wall. Check that:

• The old paint is removed from the whole agreed area, including corners and behind radiators
• The surface is matt and slightly rough, with no shiny spots
• The plaster is sound and does not crumble when you run your hand over it
• The wall is washed and free of grease and stripper residue
• The wall is dry to the touch and to the eye, with no dark damp patches
• Every crack and hole is filled and sanded
• The transition between filler and plaster is not noticeable in raking light
• The room is cleaned up and the protection is removed or ready for painting