You’ll often want to paint wood that has already been painted. How you tackle this depends on the state of the existing paintwork.

It it’s flaking off and is in generally poor condition, you will have to remove the entire paint system — primer, undercoat and top coat – by burning off with a blow-torch, applying a chemical paint stripper or rubbing with an abrasive. You then treat the stripped wood as already described for new wood.

Where the paintwork is in good condition, you simply have to clean it and sand it down lightly to provide a key for the new paint and to remove any small bits that got stuck in the surface when it was last painted. Then you can apply fresh top coat over the surface the paint system is already there.

You may, of course, need two top coats if you add a light color to a dark one to stop the color beneath from showing through.

If the paintwork is basically sound but needs localized attention, you can scrape or sand these damaged areas back to bare wood and ‘spot-treat’ them with primer and undercoat to bring the patch up to the level of the surrounding paintwork, ready for a final top coat over the entire surface.