Light switches - flush wall box dimensions

[pigface]

Do the wall boxes come in differing dimensions? I have bought a dimmer switch but the screws do no fit into the holes (in the new switch the screws are spaced slightly wider

[stanleyman]

In the UK single boxes are a standard size but varying depths. You might find that the metal box is distorted and the sides have been pushed in making it smaller across the screw holes or possibly this is a foreign non standard size. Try fitting it on a plastic box to check. If the box is distorted and plastered in then careful removal of the plaster one or both sides will allow sufficient room to open up the box to the correct position.

[DirtyHabit]

A lot of switch boxes are only 15mm deep, so you may need to fit a deeper box for a dimmer switch.