Floor tiling

First decide whether the floor is a wet room (BR18 § 339). If it is, an MK-approved membrane system must be installed — follow the guide «Wet room: membrane and tiles» before you lay tiles.

Ensure a fall to the drain. BR18 § 339 requires water on the floor to be led to a floor drain, but has no percentage requirement; as a guideline a minimum of 1 % (10 mm/m) in general and 2 % (20 mm/m) under the shower area/bath is used. The fall is created in the subfloor and checked with spirit level and folding rule before tiling.

Set out the centre line and start/end position so that edge strips are not less than half a tile's width, and so narrow strips are avoided at entrances and visible walls. Good layout planning gives a calm joint pattern and less waste.

Dry-lay the tiles (without adhesive) in a test row first to check the layout plan before you mix adhesive.

Choose adhesive to DS/EN 12004-1: C1 for dry floors with light tiles, C2 (adhesion ≥ 1.0 N/mm²) with deformability S1/S2 for wet rooms, underfloor heating and large/heavy tiles. Use adhesive from the system approval or verify compatibility with the membrane manufacturer.

Spread the adhesive with a notched trowel of the notch size the tile requires, and only lay as much as you can tile before the open time runs out. Correct for temperature — heat and draughts shorten the open time considerably.

Large formats (typically over 30 × 30 cm) require S1/S2 adhesive that can absorb movement in the substrate, and often back-buttering (adhesive on both the substrate and the back of the tile) to avoid voids under the tile. Voids create a risk of cracking under load.

Lay the tiles in the chosen bond with even joint widths — 2–3 mm for small tiles and 3–5 mm for large ones — and use crosses/spacers. Check continuously with a spirit level across several tiles that the surface is flush and level without lippage.

Place elastic movement joints in all corners and transitions (floor/wall, wall/wall) and in expansion fields: width min. 6 mm and depth approx. 2/3 of the width (BYG-ERFA, guideline). Fill them with silicone in accordance with DS/ISO 11600.

Remove adhesive residue from the joints before grouting, and grout the fixed joints with cement-based tile grout once the adhesive has cured. Wash the grout haze off the tiles while the grout is still workable.