How do I paint behind a radiator?

Behind a radiator is one of two places in a room where paint routinely stops (the other is behind the door), and the gap you have decides everything. A radiator roller reaches surprisingly well but cannot get a good finish on a narrow gap, and the wall behind a radiator is often dustier and more discoloured than the rest of the room, so it needs cleaning as well as covering.

Safety

What you'll need

• A long-handled radiator roller with a small-diameter sleeve
• A radiator brush or a long-handled cranked brush
• Dust sheets and a bin liner to protect the radiator
• A vacuum with a crevice tool, for the dust behind
• A radiator key and a bowl, if you are removing it

Step by step

1. Turn the heating off and let everything cool.Paint applied to a warm wall or a warm radiator sets too fast, drags and can blister. Turn the system off well in advance — a cast iron radiator holds heat for hours — and check by hand before you start.
2. Clean behind it before you paint anything.The gap behind a radiator collects dust, and the wall above it usually carries a dark convection stain from years of warm dusty air rising. Vacuum it out with a crevice tool, then wash the wall with a degreaser and rinse. Painting over that stain without washing gives a patch that will show.
3. Measure the gap and decide the method.Roughly: more than 30mm and a radiator roller works well. Between about 15 and 30mm and you will get coverage but not a good finish, which is fine if it is genuinely never seen. Less than that and the honest answer is to take the radiator off.
4. Protect the radiator and the floor.Tape a bin liner or a sheet over the front and top of the radiator and down to a dust sheet. A radiator roller flicks paint and the top of a radiator is exactly where it lands.
5. Use the roller in one direction and reload often.A small-diameter sleeve on a long handle holds very little paint, so work in short sections, reload frequently, and roll in one direction rather than trying to work the paint about. Do the wall above the radiator first, cutting in along the top with a cranked brush.
6. Take it off the wall if you want a proper job.Close both valves, counting and noting the turns on the lockshield so you can put it back to the same setting, drain the radiator's own water into a bowl through the bleed valve and the union, then lift it off its brackets. Modern panel radiators lift straight up and off. Paint the wall properly, let it dry, and rehang.
7. Consider taking the brackets off too.If the radiator is off, the brackets often can be as well, which lets you paint the whole wall with no interruption. Mark the screw positions before you remove them so it goes back at the same height.

Tips

• If you are replacing radiators at some point anyway, paint the wall while they are off. It is the only time the job is easy.
• A magnetic radiator dust brush or a long thin brush on a flexible handle clears the gap far better than a vacuum nozzle alone.
• The wall behind a radiator does not need the same finish coat quality as the rest of the room — but it does need the same number of coats, or it will look different from the sides.

Common mistakes

• Painting a warm radiator wall — The paint sets before it can flow, dragging and leaving heavy roller texture, and can blister where the wall is hottest.
• Not washing the convection stain off first — The dark plume above a radiator is greasy dust. Paint over it and it will discolour the new film within a year.
• Closing the valves without noting the lockshield setting — The lockshield is set to balance the system. Reopening it at random unbalances the heating and gives you cold radiators elsewhere.

Questions people ask