Epoxy Grout: When to Use It, How to Apply It, and What It Costs

You tile a commercial-style kitchen splashback with large-format stone-effect porcelain. The tiles go in perfectly. Three months later the grout joints have absorbed cooking oil and turned a dark, patchy yellow that won't clean out. No amount of specialist tile cleaner shifts it. The grout has to be removed and replaced. If you'd used epoxy grout instead of standard cementitious grout for those joints, the staining could not have happened. Epoxy grout does not absorb anything.

What epoxy grout is and how it differs from standard grout

Standard tile grout is cementitious: a mix of Portland cement, sand, and additives. It is porous at the microscopic level, which means liquids can enter the joints over time. In kitchen and bathroom environments, that porosity leads to staining, mould growth in shower joints, and eventual deterioration in areas with frequent wetting and drying.

Epoxy grout is classified as RG (reaction resin grout) under BS EN 13888. It contains no cement. Instead it is a two-part system: a resin component and a hardener component that are mixed together immediately before use. Once combined, a chemical reaction begins that causes the mixture to cure hard. The cured material is non-porous, waterproof, and resistant to a wide range of acids, alkalis, fats, and solvents.

RG classification under BS EN 13888

European standard classification for reaction resin grouts including epoxy. Distinguishes from CG (cementitious) grouts in performance requirements for chemical resistance and water absorption.

The practical implications of this chemistry are significant:

Cured epoxy grout does not stain. Cooking oil, coffee, red wine, and cleaning chemicals all wipe off the surface.
It does not support mould growth. There is nothing organic or porous for mould to take hold in.
It is genuinely waterproof, not water-resistant. Shower enclosures, wet rooms, and pool surrounds can use epoxy grout at the joints where moisture is continuous.
It is dimensionally stable. Once cured it does not shrink or crack from thermal cycling the way cement grouts can.

The trade-off is cost and application complexity. Epoxy grout costs roughly four to eight times as much as standard cementitious grout per kilogram, and it requires a methodical, skilled application to avoid the most common failure mode: smearing cured epoxy haze onto tile faces.

When to use it

Epoxy grout is not necessary for every tiling project. For most standard domestic tiling on walls with decorative glazed tiles, standard or flexible cementitious grout does the job well. Choose epoxy grout when:

Wet rooms and shower enclosures where grout is continuously wet and standard grout would degrade or discolour.
Kitchen splashbacks where cooking oils, steam, and cleaning chemicals will attack the joints regularly, particularly with natural stone or unglazed tiles where staining penetrates from the joint face.
Food preparation areas where hygiene matters and a non-porous, easy-clean joint is a requirement.
Chemical exposure: labs, utility rooms, spaces cleaned with industrial chemicals, pool surrounds.
Large-format floor tiles in high-traffic areas where the joints must stay clean under sustained mechanical and chemical stress.

For a standard bathroom tiled wall or a kitchen floor with glazed porcelain, a good quality flexible CG2 grout with a silicone joint at the change of plane (floor-to-wall, around sanitary ware) is adequate and much easier to apply. Epoxy grout is worth the extra cost and effort when staining or chemical resistance is genuinely required.

Warning

In a standard bathroom with ceramic wall tiles, epoxy grout is usually unnecessary and makes installation harder. Use it where you have a clear reason: wet rooms, food-preparation surfaces, chemical environments. Applying epoxy grout to standard tiles just to say you used a premium product is a common and expensive over-specification.

Components and mixing

A standard two-part epoxy grout consists of:

Part A (resin): the base component, typically pigmented to the desired grout colour. This is the larger of the two containers.
Part B (hardener): the curing agent, usually clear or lightly coloured, supplied in a smaller container.

The two parts must be combined at exactly the ratio specified by the manufacturer (typically by weight or by the supplied packaging proportions). Incorrect ratios prevent full cure and produce soft, weak grout. Most manufacturers supply the components pre-measured for a single pot. Do not split or combine partial amounts between mixing sessions unless you are weighing with accurate scales.

Mixing is done with a slow-speed paddle mixer (maximum 300–400rpm) until the colour is fully uniform. A streaky mix is an undermixed mix. Excessive mixing speed introduces air bubbles.

Pot life and working time

This is the most important practical difference between epoxy grout and cementitious grout: once mixed, the chemical reaction is underway and cannot be stopped. The working window (pot life) is typically 30–60 minutes at 20°C, shortening noticeably in warm conditions and lengthening in cold. Above 25°C, some epoxy grouts have a pot life of under 20 minutes. Work in the cool part of the day in summer.

Practical consequences:

Only mix as much as you can apply and clean in one session.
Prepare the joint faces and all tools before opening the components.
Have clean water and cloths ready before you start. Cleanup after the pot life expires requires solvents and considerable effort.
Work in small sections and grout them fully (apply, spread, remove excess) before moving to the next.

Do not attempt to rework epoxy grout that has partially cured in the joints. If the grout has hardened in the joints and is not yet fully cured (while still in the plastic stage, typically 2–6 hours after application), it can sometimes be scraped back. Once fully cured (typically 24 hours), epoxy grout must be removed mechanically with an oscillating multi-tool or a diamond grout saw. This is far harder to remove than cement grout.

Application technique

The application sequence for epoxy grout differs from cementitious grout in the cleanup step, which is the critical skill.

Preparation: joints must be clean and dry. Remove all tile adhesive from joint faces to the full depth, because epoxy grout does not bond well to contaminated surfaces. Mask any natural stone or textured tiles with tape before grouting: epoxy smears are very hard to remove from rough surfaces once cured.

Application: spread the grout diagonally across the tile surface with a rubber squeegee or float, pressing it firmly into the joints. Work in 1–2m² sections. The goal is to fill the joints completely with no voids.

Immediate cleanup: this is the step that separates successful epoxy grouting from a disaster. Before the grout starts to tack off (usually within 10–15 minutes of application to that section), begin the cleanup. Use a damp sponge with clean water, wrung nearly dry, to remove the surface smear in circular motions. Rinse the sponge in a bucket of clean water and squeeze out after every two or three strokes. The aim is to remove the smear progressively without flooding the joints. Change the bucket of water frequently.

Haze removal: once the joints are firm but before the grout has fully cured (2–4 hours after application depending on temperature), wipe the tile surface with a clean dry cloth to remove the epoxy haze that settles as the cleanup water evaporates. If the haze is left until full cure, it requires a specialist epoxy haze remover solvent.

Joint width and movement joints

The minimum joint width for epoxy grout follows the same standard as for other tile grouts: BS 5385-1:2018 specifies minimum widths based on tile size, with large-format tiles requiring wider joints to accommodate thermal movement. Epoxy grout, despite being rigid once cured, is specified by manufacturers for joints typically from 2mm to 10mm. Below 2mm, it is difficult to achieve full penetration; above 10mm, consider a specialist epoxy mortar.

Movement joints (expansion joints at changes of plane, around columns, and at perimeter edges of large tiled areas) must never be filled with epoxy grout or any other rigid material. They are filled with silicone sealant. Epoxy grout is rigid and cannot accommodate the movement these joints are designed to absorb; filling them with epoxy causes cracking in the adjacent tiles.

What it costs

Epoxy grout is sold by weight in pre-measured two-part kits, typically 5kg or 10kg. Coverage depends on tile size and joint width: for 600×600 tiles with a 3mm joint, a 5kg kit covers roughly 8–12m² of floor.

Product type	Coverage (5kg kit)	Indicative price per 5kg	Suitable for
Standard cementitious CG2 grout	8–15m² at 3mm joints	£9 – £15	Walls, floors, standard wet areas
Flexible CG2S grout	8–15m² at 3mm joints	£12 – £22	Floors, deformable substrates, exterior
Two-part epoxy grout (RG)	6–12m² at 3mm joints	£35 – £85	Wet rooms, kitchens, chemical resistance

Hiring a professional tiler for epoxy grouting adds a labour premium over standard grouting. The speed constraint (pot life), higher material cost, and skill required for the cleanup mean most tilers charge 20–40% more per m² to use epoxy grout rather than cementitious grout.

Choosing a colour

Epoxy grout is supplied in a narrower range of colours than cementitious grout, though the major manufacturers offer several dozen options. The colour choice affects more than appearance:

Light grouts in wet rooms: white and pale grey are popular but show any staining from hard water or mineral deposits. In a hard-water area, a mid-grey tends to age more gracefully.
Colour matching to tiles: large-format tiles with minimal joints look best with a close colour match. Contrasting grout in a wet room draws attention to every joint width variation.
Batch consistency: if the installation spans multiple days and you are using partial pots, make sure all the product comes from the same manufacturing batch. Batch-to-batch colour variation is more pronounced in epoxy grouts than in cement grouts.

Epoxy grout colour is stable once cured. Unlike cement grout it will not bleach, darken with moisture, or stain from the tile adhesive bleeding into the joint face during setting.

Storage and shelf life

Unmixed epoxy grout components have a shelf life of 12–24 months from manufacture when stored at room temperature in sealed containers. Heat accelerates degradation. Do not store in unheated sheds or vehicles where summer temperatures exceed 30°C. Cold storage is less harmful, but the resin may become viscous and need gentle warming before mixing.

Once mixed, the product must be used within the pot life. There is no safe way to extend pot life once mixing has begun. Partially used pots of mixed grout cannot be stored and reused.

Check the expiry date on both components before starting. Using an expired hardener with an in-date resin will produce an incomplete cure. Both components must be in date.

What can go wrong

Epoxy haze on tiles: cured epoxy smear that wasn't removed during the cleanup window. Requires specialist epoxy haze remover and hard scrubbing. The only prevention is thorough, prompt cleanup during application.

Soft or weak cure: usually the result of incorrect mixing ratio or inadequate mixing. The grout will feel rubbery rather than hard after 24 hours. It cannot be rescued. It must be removed and the joints redone.

Discolouration at the surface: some pigmented epoxy grouts are UV-sensitive; check manufacturer guidance for exterior or conservatory applications with high UV exposure.

Cracking at movement joints: epoxy grout incorrectly placed in movement joints. Remove and replace with flexible sealant.

Removing old epoxy grout

Epoxy grout that has fully cured is the hardest of all grout types to remove. Unlike cement grout, which can be dissolved or softened with acid-based grout removers, epoxy grout must be removed mechanically. The standard tools are an oscillating multi-tool with a grout-raking blade, or a diamond-tipped grout saw. Both are effective but slow, and both carry a risk of chipping tile edges on dense large-format tiles.

For a complete re-grout of an epoxy-grouted tiled area, allow at minimum three times the removal time you would expect for a cementitious grout job. On a 2m² tiled shower enclosure, a full epoxy grout removal and re-grout is typically a full day's work for a skilled tiler.

The difficulty of removal is itself a reason to use epoxy grout only where its properties are genuinely required. Applied to a standard bathroom wall where a simple cementitious re-grout might be done in two hours, a future epoxy removal job becomes a disproportionately disruptive task.

Health and safety

Epoxy resin components are skin sensitisers. The hardener in particular can cause sensitisation reactions with repeated unprotected skin contact. Once sensitised, a person may react to even trace exposures. Wear nitrile or rubber gloves throughout the mixing and application process. Eye protection is recommended during mixing, which can produce fine droplets.

Ventilate the working area during application. The resin has a low-level odour that is not immediately harmful at normal domestic concentrations but can be unpleasant in an enclosed shower enclosure or bathroom with no ventilation.

Dispose of mixed waste grout in solid waste (as hardened material after cure), not down the drain. Uncured epoxy is a hazardous substance that should not be introduced to drainage systems.