Tile Backer Board for Showers: Do You Need It?

Backer board gives the tile adhesive a stable, flat surface that does not soften when it gets wet. Ordinary plasterboard has a paper face that swells and loses strength once water finds its way through a cracked grout line, and when that happens the tiles loosen, the grout cracks further and the leak speeds up.

Backer boards are made from materials that tolerate moisture, such as cement-based or foam-cored boards. They are also lighter than a sand and cement render, which matters on timber stud walls and upstairs floors.

Inside a shower area on a stud wall, some form of water-resistant board is the norm; standard plasterboard is the wrong base there. On masonry walls with sound plaster, tiling onto the plaster with suitable tanking can be fine. Where old plaster is soft, hollow or has been soaked by a past leak, stripping back and boarding is often more reliable than patching.

On timber floors under tiles, a suitable board helps stop the flex that cracks grout and tiles.

Backer board resists water, but water still gets through the joints between boards and around screws, the tray edge and the valve. That is why those points are sealed with tape and a tanking membrane, and why in the direct spray area many fitters tank the whole board face.

Think of it as two jobs: the board gives a sound base, the tanking stops water reaching the wall behind. Skip either and the shower is relying on grout alone, which is not waterproof.

Using ordinary plasterboard in the shower zone is the most common. After that come board joints left untaped, boards fixed with too few screws so they flex, and no sealing where the board meets the shower tray. Tiling straight onto board that is not flat is another: the tiles end up with voids behind them and sound hollow, and those voids trap water.

The tray itself should be fitted, level and supported before boarding, with the board finishing above the tray lip so water runs into the tray, not behind it.

If the tiles around your shower are sound and the wall behind is dry and firm, you may not need to strip back at all. If tiles are loose, grout keeps cracking, or there is staining on the ceiling below, the wall underneath is often part of the problem, and new tiles on the old base will fail again. Boarding at that point adds a little to the job and a lot to its life.

We tile showers and bathrooms, and we check the wall before quoting so you know whether boarding and tanking are needed. Send photos of the shower walls, any loose or hollow tiles and the ceiling below. We give fixed written quotes after seeing the room, and quotes are free.