Tile and Stone Floorcovering Installation
Tile and stone questions test substrate adequacy, thinset coverage, joint design and movement accommodation. Natural stone adds sealing and membrane requirements.
Substrate and deflection
- Deflection must be L/360 minimum for ceramic and porcelain, and often stiffer for stone; check joist span and add blocking or a second layer if needed.
- Cement backer board, 1/4 in. on floors, embedded in thinset and fastened per manufacturer, with alkali-resistant mesh tape at joints.
- Waterproofing membrane in wet areas and over wood-framed substrates for stone.
- Concrete must be cured, clean, flat and free of curing compound.
Setting
- Notch size follows tile size: larger tile means a deeper notch plus back-buttering. Check coverage by lifting a tile - 80% in dry areas, 95% in wet areas or exterior.
- Key thinset into the substrate with the flat side of the trowel, then comb in one direction.
- Respect open time; thinset that has skinned over must be removed and replaced.
- Use levelling clips on large-format tile to control lippage.
Joints and grout
- Minimum joint about 1/16 in. for ceramic and 1/8 in. for stone; sanded grout for wider joints, unsanded for narrow.
- Movement joints at the perimeter, at changes of plane, and roughly every 20-25 ft interior. Never grout tight to a wall.
- Seal stone and grout as specified; some stones need sealing before grouting.
Worked example
Installing 12 × 24 in. porcelain over plywood: add a backer board or uncoupling membrane, set with a 1/2 × 1/2 in. square notch plus back-buttering, maintain a 1/8 in. joint with levelling clips, and keep a 1/4 in. gap at the perimeter filled with sealant. Grout only after the thinset has cured.
Traps
- Screwing backer board down without thinset beneath it, leaving voids that crack tile.
- Grouting to the wall with no perimeter gap, so the field tents.
- Mixing thinset too stiff or too wet, which changes bond strength.
- Grouting too soon or washing too wet, weakening the grout.
Repair, Renovation and Finishing Details
Repair, renovation and finishing details test diagnosis, colour and pattern matching, and neat transitions. The exam wants you to find the cause before patching, and to know which trim or filler belongs where.
Diagnose before repairing
- Establish why it failed: moisture, substrate movement, no expansion gap, adhesive failure or impact. A patch over an active moisture problem fails again.
- Check for asbestos and lead before cutting into older resilient or painted trim.
Patch and replace
- Sheet vinyl: cut a neat plug or straight-edged patch, match pattern and dye lot, seal or weld the seam, then roll.
- LVT and SPC: cut out the damaged plank along its edges, clean the adhesive, install the replacement and roll; keep spare boxes from the original lot.
- Carpet: re-stretch before patching; take a patch from a closet if no matching remnant exists; seal the edges.
- Hardwood: cut out the board down the centre, split it out, cut the new tongue, blind-nail and set, then sand and finish to blend.
- Tile: score and remove grout, break out the tile from the centre, chip off old thinset, check the substrate, set the new tile and regrout.
Transitions and trim
- T-mould for floors of equal height, reducer for height differences, threshold at exterior doors, stair nose at nosings.
- Base shoe and quarter round cover the expansion gap; cove base in commercial work; caulk where materials change.
- Leave the expansion gap behind base - never fill it with grout or hard adhesive.
Finishing and closeout
- Clean per the manufacturer: no wax or abrasive on factory-finished urethane, and no wet washing during adhesive cure.
- Protect finished floors and complete a punch list: seams, lippage, transitions, gaps, cleanliness.
- Provide care instructions and leftover material to the client.
Worked example
A single cracked tile in the middle of a field. Rather than chiselling randomly, score the grout around it, remove the tile in pieces from the centre outward, grind the thinset flat, confirm the substrate is not hollow, then set a matching tile with full coverage, regrout, and check lippage against the neighbours.
Traps
- Patching without finding the moisture source.
- Using a patch from a different dye lot in a visible area.
- Smearing caulk over a movement joint that needs a proper sealant joint design.
- Cleaning new resilient with a solvent that dulls the wear layer.