Grouting, Sealing and Finishing
This domain tests the finish: grout mixed and applied correctly, joints full and even, movement joints kept flexible, and surfaces sealed only when the time is right.
Rules
- Wait for the adhesive to cure as stated, usually about 24 hours, before grouting.
- Clean the joints to a uniform depth, roughly two-thirds of the tile thickness, and remove all adhesive nibs.
- Choose the grout: sanded cementitious for joints of 3 mm and wider, unsanded for narrow joints and polished or soft stone, epoxy for chemical resistance and heavy-duty areas. Check colour and batch against the approved sample.
- Mix to a firm paste, spread diagonally with a rubber float, strike off, then let it firm before the first sponge pass; a second pass follows, and haze is polished off when dry.
- Keep movement joints flexible: silicone or polyurethane at perimeters, between different substrates, and at the intervals on the drawing. Never fill them with rigid grout.
- Seal porous stone and unglazed tiles after the grout has cured, using an impregnating sealer.
Worked example
A 12 m² floor with 600×600 tiles and 3 mm joints. The manufacturer's chart gives about 0.45 kg/m², so 12 × 0.45 = 5.4 kg, plus 10% waste = 5.94 kg. A single 5 kg bag is short; take a 10 kg bag or two 5 kg bags, and keep a spare for touch-ups. Reasoning: grout is cheap, but a patchy joint colour from running out mid-floor is not.
Traps that cost marks
- Grouting before the adhesive has cured.
- A soaking sponge that washes out the joint and weakens the grout.
- Leaving haze until it sets hard.
- Rigid grout in a movement joint, which then cracks.
- Sealing before the grout is dry.