How do i tile a shower niche properly so it doesn't leak — my last contractor in Moncton did it wrong and water got behind the wall?

A properly waterproofed shower niche is all about what happens before a single tile goes up — the waterproofing membrane is everything, and it sounds like your last contractor skipped or rushed that step.

The most common failure point isn't the grout or the tiles themselves — it's the substrate and membrane behind them. Here's how to do it right.

Start with the right substrate. Regular drywall or green board have no place inside a shower niche, full stop. You need either cement board (Durock, HardieBacker) or a foam shower board like Schluter Kerdi-Board or Wedi. These won't swell, rot, or delaminate when moisture inevitably gets through the tile layer — because it always does, eventually.

The waterproofing membrane is non-negotiable. Every surface inside that niche — back wall, two side walls, the floor (called the sill), and the top — needs to be coated with a continuous waterproofing membrane before tiling. Popular options include Schluter Kerdi sheet membrane, RedGard liquid membrane, or Mapei AquaDefense. If you're using liquid membrane, apply two coats and pay obsessive attention to the corners, which are the highest-risk spots for failure. Fabric-reinforced corners (pre-made corner pieces are available for Kerdi and similar systems) add another layer of protection where the walls meet. Every seam and corner needs to be embedded in the membrane, not just painted over.

The sill must slope outward. This is the detail that separates a professional install from a callback. The bottom shelf of the niche needs a slight pitch — roughly 1/8 inch per foot — sloping toward the shower interior so water drains out rather than pooling against the back wall. This is done during framing or substrate installation, not fixed with extra thinset later.

Tiling sequence matters. Set the back wall tiles first, then the sides, then the sill tiles last so they overlap and shed water forward. Use a polymer-modified thinset rated for wet areas — standard thinset isn't adequate here. For the sill, a single piece of tile or stone (no grout joint running front-to-back) is ideal. If you must use multiple tiles on the sill, keep grout joints to a minimum and seal them religiously.

Grout and caulk placement. All inside corners — where the niche walls meet each other and where the niche meets the surrounding shower wall — get caulk, not grout. Grout is rigid and will crack at those movement joints within a year or two. Use a silicone or siliconized latex caulk that matches your grout color. The flat surfaces get sanded or unsanded grout depending on joint width (under 1/8" = unsanded), sealed after curing.

After installation, do a flood test. Tape plastic sheeting over the niche opening, fill the shelf with water, and leave it for 24 hours. Check the wall cavity behind the niche for any moisture. This is the same test a good inspector would do before closing up walls.

In terms of cost if you're hiring this out in Moncton, a properly done niche as part of a full shower tile job typically adds $200–$500 to the overall tile labour cost, depending on size and complexity. The materials for proper waterproofing (Kerdi or RedGard, corner pieces, membrane tape) run $80–$150 for a standard niche.

Given your experience with the last contractor, it's worth asking any new tile setter specifically: "What waterproofing system do you use, and how do you handle the niche corners?" A confident, specific answer tells you a lot. You can also browse the New Brunswick Construction Network directory to find experienced tile contractors in the Moncton and Greater Moncton area who can assess whether your existing niche needs to be torn out and redone — sometimes a repair is possible, but if water has already gotten into the wall cavity, you may be dealing with mould remediation before retiling.