Epoxy grout

Epoxy grout is a two-part compound based on epoxy resin and a hardener, used to fill the joints between tiles. Once cured it practically does not absorb water, steam or grease, so mould does not grow on it and the joint colour stays even. Cement grout, by contrast, is porous: in a bathroom or on a backsplash it darkens over time and can grow mould.

Where to use it. Shower zones and walls around a bath; bathroom floors; kitchen backsplashes; pools and saunas; spaces with heavy use and frequent washing where hygiene matters; light or contrasting joints whose colour must stay put. In dry rooms and on ordinary floors a good cement grout with polymer additives is usually enough.

How to work with it. It is a demanding material. The components must be dosed precisely and mixed thoroughly, otherwise lumps appear and the compound does not fill the joint completely. Working time is limited: it sets quickly and dried excess is hard to remove, so joints are filled in small sections and the film is washed off at once. The exact pot life and consumption are given by the manufacturer in the technical data sheet: they depend on the brand and temperature. There are two-part compounds in tubes mixed in the nozzle as they are squeezed out, which are easier for small areas.

Joint width and consumption. The permitted joint width depends on the brand: the range of different epoxy grouts can be, for example, up to 10 mm or up to 15 mm, so choose by the data sheet. The wider the joint, the higher the consumption: wide joints (5–10 mm) need 2–3 times more grout than narrow ones. For large-format tile with a minimal joint, consumption is small, but the filling must be complete, without voids.

What costs more and what pays back. Epoxy is noticeably more expensive than cement grout, several times so, and needs a more experienced installer. But it keeps its look longer and the joints do not need refreshing. If you need to save, it is more sensible to put epoxy in the wettest zones (shower) and on the backsplash and use a good latex-modified cement grout elsewhere.

Typical mistakes: grouting with epoxy before the adhesive has fully cured; thinning the mix with water; mixing a large batch that cannot be used in time; leaving excess to dry; choosing the colour without a sample. Epoxy grout does not replace waterproofing: the joints protect the surface, but waterproofing under the tile is still required. We state the grout type in the finishes schedule so the contractor does not swap it for a cheaper one.