Hiring a Tile Installer: Substrate, Waterproofing, the Quote

Square footage by area and surface; the tile by size and type, or an allowance per square foot if you're choosing; the substrate — cement board or which uncoupling membrane; the mortar by type; for a wet area, the waterproofing method (liquid, sheet or foam board, the pan or tray, and a flood test); the layout and offset; the grout type and the silicone at changes of plane; edge treatment (bullnose or metal profile); demolition, self-leveling and subfloor repair as separate lines; transitions and base; the schedule; and a warranty. If the quote says 'install tile' and a number, it isn't one.

Look for a tile contractor — not a flooring generalist — who can name the TCNA method for your job, has a Certified Tile Installer (CTI) on the crew or holds the credential, and belongs to the NTCA or shows work older than a year. Tile showrooms keep lists of the setters whose work comes back without complaints. Ask to see a shower they built five years ago; anyone can show you one from last month.

A credential from the Ceramic Tile Education Foundation: a written exam on industry standards and a hands-on test in which the installer builds a mock-up with cuts, a niche, a pattern and waterproofing under a proctor's eye, to tolerance, in a time limit. It's the only independent, hands-on test in the trade. A CTI number is worth 10–20% on the labor and is the single best filter for a shower or a large-format floor.

The Tile Council of North America's Handbook lists numbered methods for every combination of substrate, tile and use — F125 for a membrane over wood, B415 for a waterproofed shower, and so on — with the materials and steps for each. A setter who says 'we're doing an F125 with a bonded membrane and modified mortar over it' is telling you the job is built to a published standard a manufacturer will warranty. A setter who's never heard of it is improvising.

One of three ways, all of them a continuous membrane behind the tile: a liquid-applied membrane rolled over cement board with fabric in the corners and around the niche; a sheet membrane bonded to board with sealed seams; or a foam board system with sealed joints. The pan is a pre-slope and a bonded drain or a foam tray, and the drain has to match the membrane. Before tile, the pan is flood-tested for 24 hours. A quote that says 'cement board and tile' with no membrane is a shower that leaks.

A deposit that covers the tile order if the contractor is buying it (30% is common), a progress payment after substrate and waterproofing pass — that's the flood test on a shower — and the balance on completion after your walk-through. For a floor, deposit and balance. Don't pay for grouting before you've seen the set tile.

Tile straight to plywood or drywall; 'mastic' on a floor or in a shower; no membrane in a wet area; a 50% offset on 12 × 24 tile with no leveling system; no mention of substrate or prep; a price per square foot with no scope; no insurance; and a portfolio of showers all under a year old. Also a quote far below the others, which usually means the prep and the waterproofing are missing.

The tile has a manufacturer's warranty that assumes correct installation; the membrane and mortar makers warranty their systems when installed to their instructions, sometimes for 10–25 years. What matters is the installer's workmanship warranty — cracked or loose tile, failed grout, leaks — for at least a year and ideally two or three, in writing. A setter who won't warranty a shower doesn't trust their own waterproofing.