Does a shower need waterproofing under the tiles?

Many people think tiles are waterproof on their own. Their surface may be, but the grout jointsGrout jointThe gap between tiles, slabs or stones, and the material that fills it. Grouting means filling these joints, which locks the surface together and keeps out water and dirt. between them let a little water through, especially over the years, and so do small cracksCrackA split or gap in render, concrete, a wall, a coating or wood. Fine cracks are usually only on the surface; ones that grow, keep reopening or run diagonally need attention. and the joints around the drainFloor drainThe outlet in a floor where water drains away on roofs, balconies and in bathrooms, with a grate on top and usually a trap below. and the pipes. The water that gets through stays underneath, in the renderRender (plaster)A layer of mortar (sand, cement or lime, and water) spread over brick or concrete to give a wall a straight, sound surface ready for paint or tiles. and the floor.

That is why, in the areas that get wet, a waterproofingWaterproofingThe work and materials that stop water getting through on flat roofs, balconies, bathrooms, basements, planters and tanks. layer is commonly laid before the tiles: on the shower floor and its walls, up to a height that depends on where the shower head is. In the corners, where wall meets floor, and around the drain and the pipes, the waterproofing is reinforced, because those are the joints that open up first.

In a walk-in showerWalk-in showerA shower with no tray and no step, level with the rest of the bathroom floor. The water drains through a floor drain or a linear channel drain. this matters even more. With no tray, the floor itself has to hold the water and send it to the drain. In the bathroom with the green bathtub, and in the one with the channel drain under the window, the floor was laid again with a slopeFalls (drainage slope)The gentle slope built into flat roofs, balconies and bathroom floors so water runs to the drain or gutter instead of pooling. before tiling.

Waterproofing can't be seen once the tiles are down, and it can't be fixed without stripping them out. Ask beforehand how it will be done and how high up the walls it will go. If you already see a stain on the ceiling of the flat below, or render bulging next to the shower, the cause may be a leaking pipe or water getting through grout and silicone. Which of the two it is can be judged on site.