Back boxes are the boxes set into, or fixed onto, a wall to hold sockets and switches. Choose the back box depth to suit the accessory. Plain switches fit 16–25mm, while USB sockets, dimmers and cooker switches usually need 35mm or 47mm.
Types of Back Box
Metal back boxes: flush mounted in brick or block walls
Dry lining back boxes: for plasterboard walls, with fixing lugs
Pattress boxes: surface mounted where the wall can't be chased
Single, double and twin gang sizes
Back Box Depths
16mm and 25mm: standard light switches and slim plates
35mm: USB sockets, dimmers and most decorative metal sockets
47mm: smart switches, cooker switches and deep accessories
