Grout Calculator

It depends on joint width, joint depth and tile size, not just on area. The joint is filled for the full tile thickness, so a thicker tile with the same joint width uses proportionally more.

Typically 2 to 3 mm for rectified wall tiles and 3 to 5 mm for floor tiles. Wider joints accommodate size variation between tiles, which is why less precisely made tiles need them.

Sanded grout is used for joints above about 3 mm, where the sand prevents shrinkage cracking. Unsanded is for narrow joints and for polished stone, which sand would scratch.

Usually movement — a substrate that flexes, or no movement joints in a large area. Grout is rigid and brittle, so anywhere the structure moves needs a flexible sealant joint rather than grout.

Cement-based grout is porous and benefits from sealing in wet areas. Epoxy grout needs no sealing but is considerably harder to work with and more expensive.

Usually 24 hours for light foot traffic and longer before wetting, though it varies by product. Grouting too soon after tiling traps moisture in the adhesive beneath.

A matching grout makes the surface read as one field; a contrasting one emphasises the grid. Practically, mid-tones show dirt least — white grout on a floor is the hardest to keep looking new.

A damp sponge while the grout is still fresh removes most of it, and a proprietary haze remover handles what sets. Leaving it too long makes it far harder, particularly on textured tiles.

Only if enough old grout is removed to give a meaningful depth for the new — typically at least 2 mm. A thin skim over existing grout will not bond and will fail quickly.

Usually inconsistent water in the mix between batches, or grouting over adhesive that had not fully cured so moisture varied. Both are permanent once set.

Wet areas, chemical exposure and anywhere staining is unacceptable. It needs no sealing and is considerably harder to apply — it sets fast and cleaning it off tiles once cured is very difficult.

Sanded grout handles up to about 12 mm; beyond that the joint is generally filled with mortar rather than grout. Very wide joints also shrink more and are more likely to crack.