Tile Backer Board: A Guide

Tile backer board is a rigid board made for tiling onto. Common types include cement-based boards and lightweight boards with a foam core and a coated face that tile adhesive bonds to. Unlike gypsum plasterboard, they don't soften when they get wet, and many foam-core boards are waterproof in their own right once the joints are sealed correctly.

Tiling on plasterboard is fine in dry areas, as long as the board is sound, well fixed and primed, and the tiles are within its weight limit. Moisture-resistant plasterboard copes with humid rooms but isn't designed to be soaked. Tile backer board is made for tiling and for wet areas.

Tanking is the waterproofing layer: a membrane or liquid coating applied over walls and floors, with sealed joints and corners. In a shower, it's the tanking or a fully sealed waterproof board system that keeps water out of the wall, not the tiles or the grout.

Inside showers, around baths and in wet rooms, walls are usually boarded with tile backer board and then waterproofed, or built with a waterproof board system with every joint and fixing sealed. This avoids the common failure where water gets through the grout, the plaster or plasterboard behind softens, and the tiles come loose.

Backer boards are fixed to studs or solid walls with the fixings and spacings the board manufacturer specifies, often with special washers on foam-core boards. Joints are taped and sealed with the system's own tape and sealant, and in wet areas the corners and pipe holes are sealed too. Follow the manufacturer's instructions, because each system is designed to be used as a set.

Some walls shouldn't be tiled as they are: crumbling or blown plaster, layers of old paint or wallpaper, walls that are badly out of flat, timber cladding, and stud walls that flex. In these cases the wall is usually stripped and boarded with tile backer board, giving a flat, sound surface to tile.

Robert does full plasterboard and wall alterations, so walls can be boarded and prepared as part of the tiling job rather than handed over to another trade first.