Tile Grout: Types, Colours, Coverage, and How to Get Clean Joints

You've tiled a splashback. The adhesive has cured, the tiles look perfect, and now you need to fill the joints. So you grab a bag of grout from the shelf, mix it up, and start spreading. Two weeks later the grout between your floor tiles has cracked. The grout on the splashback has stained yellow from cooking oil. And the grout in the corners of your shower is already peeling away. Three different problems, three different causes, all preventable if you'd picked the right grout and applied it correctly.

What it is and what it's for

Grout is the material that fills the joints between tiles after the adhesive has set. It serves two purposes: it prevents dirt and moisture from getting behind the tiles, and it gives the tiled surface a finished appearance. Without grout, tile edges are exposed, debris collects in the gaps, and water finds its way into the substrate where it causes damage you won't see until it's serious.

Grout is not adhesive. It doesn't hold tiles in place. That's the adhesive's job. Grout fills and seals the joints between tiles that are already fixed. This distinction matters because people sometimes try to use grout to secure loose tiles. It won't work. If a tile is moving, the adhesive has failed and you need to re-fix it before grouting.

The relevant British Standard is BS EN 13888, which classifies grouts into two families: CG (cementitious grout) and RG (reaction resin grout, which includes epoxy). Joint width requirements come from BS 5385-1:2018, which specifies minimum 2mm joints for tiles smaller than 0.1m2, 3mm for tiles between 0.1m2 and 1m2, and 5mm or wider for large ceramic panels. Your tiler should know these. If you're tiling yourself, they prevent cracking from thermal movement.

Types of grout

There are three types you'll encounter in UK retailers. Each one suits a different application, and getting this wrong is the most common grouting mistake homeowners make.

Standard cementitious grout

The cheapest option. Mapei Keracolor FF is a good example at around £9.5 for a 5kg bag. It handles joints up to 6mm, sets in about 24 hours, and comes in a decent range of colours. It's classified CG2 under BS EN 13888, meaning it meets the "improved" standard for water absorption and abrasion resistance (the suffixes W and A indicate those properties, so CG2WA is the top-tier cementitious classification).

Standard cementitious grout is fine for wall tiles in dry areas. Kitchen splashbacks, bathroom walls above the splash zone, utility room walls. It's not suitable for floors because it can't handle the flex and movement that floor substrates experience.

Flexible grout

This is what you should use for almost every domestic tiling job. The polymer additives give the cured grout enough flex to absorb minor substrate movement without cracking. That matters on floors (which deflect under load), on underfloor heating (which expands and contracts with temperature cycles), and on plywood or cement board substrates (which move more than masonry).

Mapei Ultracolor Plus at £21.49 for 5kg from Screwfix is the product professional tilers reach for most often. It carries the CG2WA classification (the highest cementitious grade), sets in 2-4 hours, handles joints from 2-20mm, and includes mould resistance. BAL Micromax 3 ECO is the other main professional choice at £26 – £29 for 5kg, with Microban antimicrobial treatment and joints up to 30mm.

Epoxy grout

Epoxy is a two-part system (resin plus hardener) that cures by chemical reaction rather than cement hydration. The result is non-porous, stain-proof, and chemically resistant. It doesn't need sealing. It won't absorb cooking oils or red wine. It's the right choice for tiled kitchen worktops, food preparation surfaces, and environments where chemical resistance matters.

The catch is cost and difficulty. BAL Absolute Grout costs around £32.5 for a 2kg tub from specialist suppliers (and up to £57 from general retailers). That's 3-5 times more per kilogram than flexible cementitious grout. And the application is less forgiving: you have about 60 minutes of pot life at 20C before the mixed grout starts to harden. Once it sets on the tile face, removing it is a nightmare.

Professional tilers on UK forums consistently say the same thing: epoxy is for worktops, pools, and commercial food prep areas. For a standard kitchen splashback, flexible cementitious grout with a quality sealer is perfectly adequate.

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The hybrid option most guides miss

Kerakoll Fugabella Color is a hybrid resin-cement grout that professional UK tilers rate highly but most homeowner guides don't mention. It applies like cementitious grout (long working time, forgiving cleanup) but cures to a non-porous, stain-resistant finish closer to epoxy. It comes in 50 colours, suits underfloor heating, and costs around £16.2 for 3kg. If you want better stain resistance than standard flexible grout but don't fancy wrestling with epoxy, Fugabella is the middle ground.

How to work with grout

Grouting is one of those jobs that looks simple but has a narrow window where everything needs to happen in the right order. Rush it and you'll pull grout from the joints. Wait too long and you'll spend hours scrubbing haze off tile faces.

Before you start

Wait a minimum of 24 hours after tiling. 48 hours is better. The adhesive needs to fully cure before you apply any pressure to the tile edges with a grout float. If you used rapid-set adhesive, check the manufacturer's instructions, but even with rapid-set, same-day grouting is risky for floor tiles.

Gather your tools: a rubber grout float, a large sponge (not a kitchen sponge; buy a proper tiling sponge), a bucket of clean water, a mixing bucket, and a paddle mixer attachment for your drill. You'll also need tile spacers removed and joints cleaned of any adhesive squeeze-out.

Mixing

This is where colour consistency lives or dies. Professional tilers use measuring containers for the water, the same container every time, so every batch has exactly the same water-to-powder ratio. Inconsistent mixing is the number one cause of colour variation across a tiled surface. Use a paddle mixer attachment on a drill, not a stick. Mix to a smooth, thick paste, like peanut butter. No lumps, no dry pockets.

Applying

Load the float with grout and spread it diagonally across the tile joints. Diagonal is critical. If you drag the float along the joint line, the edge of the float dips into the joint and pulls grout back out.

Work in sections of about 1-2m2 at a time. Push the grout firmly into the joints, making sure they're completely filled with no voids or air bubbles. Then scrape excess grout off the tile surface with the float held at a steep angle (about 45 degrees), again moving diagonally.

The cleanup window

This is the part that catches beginners. After spreading, you need to wait until the grout has firmed up in the joints but hasn't fully hardened on the tile face. The timing depends on temperature, humidity, and the specific grout product. There's no universal number. Watch the grout, not the clock.

The test: press your finger lightly on the grout in a joint. If it's firm and doesn't deform, but the residue on the tile face still wipes off with a damp sponge, you're in the window. For most flexible grouts at room temperature, that's roughly 15-30 minutes after application.

Wipe with a damp sponge using light, diagonal strokes. Rinse the sponge frequently in clean water. Don't over-wash. Excessive water on the surface pulls pigment from the grout and causes colour lightening, a problem that BAL grouts are particularly susceptible to.

After the initial sponge clean, let the grout cure for another hour or so, then polish any remaining haze off with a dry microfibre cloth.

Where NOT to grout

This is the single most important rule in grouting, and the one DIYers get wrong most often.

How much do you need

Grout coverage depends on tile size, joint width, and joint depth (which is determined by tile thickness). Smaller tiles with wider joints use more grout per square metre because there are more linear metres of joint to fill.

The formula is:

kg per m2 = (Tile Length + Tile Width) x Joint Width x Joint Depth x 1.8 / (Tile Length x Tile Width)

All dimensions in millimetres. The 1.8 factor accounts for grout density. Here's what that works out to for common tile sizes:

Add 10-15% for waste. You'll lose grout on the float, in the mixing bucket, and during cleanup.

For a typical kitchen splashback of 2-3m2 using 300 x 600mm tiles with 3mm joints, a single 2.5kg bag is plenty. For a 24m2 kitchen floor using 600 x 600mm tiles with 3mm joints, one 5kg bag should cover it with some to spare.

Colour selection

Grout colour changes the entire look of a tiled surface. The same tile with white grout and dark grey grout will look like two different rooms.

Match the tile for a uniform, continuous appearance. This is the safe choice for floors and large wall areas. The grout disappears and the tile pattern dominates.

Contrast the grout to emphasise the tile layout. Dark grout on white metro tiles is a classic example. This highlights every tile and makes the grid pattern a feature. Be aware that contrasting grout shows any inconsistency in joint width, so the tiling needs to be precise.

Avoid white grout on floors. It stains. Grey or a colour that matches the tile is a better long-term choice. Even sealed white grout on a kitchen floor will eventually discolour in high-traffic areas.

Most major brands offer 10-15 standard colours. Mapei Ultracolor Plus comes in over 30. If you need an exact match, Kerakoll Fugabella offers 50 colours.

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Cost and where to buy

Grout prices vary by type. The typical range is £9 – £22 per 5kg bag for cementitious grouts, but that widens once you include epoxy.

Budget cementitious: Mapei Keracolor FF 5kg at £9.48, or Everbuild 730 Universal Flexible at around £8.7 (both inc. VAT). Perfectly adequate for interior wall tiling with narrow joints.

Mid-range flexible: Mapei Anti-Mould Flexible 5kg at £19.5 from Wickes. A good all-rounder for walls and floors. Mapei Flexible 2.5kg bags are £10 from Wickes if you only need a small quantity.

Premium flexible: Mapei Ultracolor Plus 5kg at £21.49 from Screwfix (CG2WA rated, fast-setting, mould-resistant). BAL Micromax 3 ECO 5kg at £26 – £29 from specialist retailers. These are what professional tilers use daily.

Hybrid: Kerakoll Fugabella Color 3kg at £16.2 from Tile Fix Direct. Not widely stocked by the big chains but available from tiling specialists and online.

Epoxy: BAL Absolute 2kg at £32.5 from specialist suppliers. Mapei Kerapoxy from £47+. Only buy epoxy if you're tiling a worktop or food prep surface. For everything else, flexible cementitious with a sealer is better value and easier to apply.

All five major UK merchants stock grout: Screwfix, Toolstation, Wickes, Travis Perkins, and Jewson. Screwfix and Wickes have the widest retail range. For specialist products like Kerakoll Fugabella or BAL Absolute epoxy, try Pro Tiler Tools, Sealant Supplies, or Tile Fix Direct online.

Sealing grout

Cementitious grout is porous. Without a sealer, it absorbs moisture, cooking oils, food splashes, and dirt. The grout darkens, stains, and eventually supports mould growth. Seal it.

Apply grout sealer after the grout has fully cured, typically 48-72 hours after grouting. Use a product like HG Super Protector (dries colourless in 24 hours on walls, 36-48 hours on floors) or LTP Mattstone for a natural finish. Apply with a small brush along the grout lines or spray on and wipe excess from tile faces.

Reseal every 1-2 years in kitchens and bathrooms. High-traffic kitchen floors may need annual resealing.

Epoxy grout does not need sealing. Its non-porous surface repels stains without any treatment. That's one of the reasons professional tilers specify it for worktops despite the higher cost and harder application.

Alternatives

Flexible cementitious vs epoxy is the main decision. For most domestic kitchen and bathroom tiling, flexible cementitious grout with a quality sealer is the right answer. Epoxy is overkill unless you're tiling a worktop.

Kerakoll Fugabella splits the difference. If stain resistance matters but you don't want the stress of epoxy's short working time, this hybrid option is worth the premium over standard flexible grout.

Silicone sealant is not an alternative to grout. It's a complement. You need both: grout for flat surfaces, silicone for corners and junctions. They do different jobs.

Where you'll need this

• Flooring - flexible grout for filling joints between floor tiles
• Tiling - grouting wall tiles on splashbacks and feature walls

Grout appears in the second fix phase of any extension, renovation, or new-build project wherever tiles are used. It's one of the last materials applied and one of the most visible, so getting it right matters more than most people expect.

Common mistakes

Grouting too soon. The adhesive hasn't cured and the tiles shift under pressure from the grout float. Wait 24 hours minimum, 48 ideally.

Inconsistent water ratio between batches. The first section of your floor is dark grey. The second section is light grey. Same bag of grout, different amount of water. Use a measuring container for the water every single time.

Grouting corners. Already covered above, but it bears repeating because it's so common. Internal corners and perimeter junctions get silicone, not grout. Every time.

Over-washing during cleanup. You're pulling pigment out of the joints. Light, diagonal strokes with a damp sponge. Not soaking wet, not scrubbing hard. Change the water frequently.

Skipping the sealer. Unsealed cementitious grout in a kitchen will stain within weeks. It's a ten-minute job that saves you re-grouting later.

Using standard cementitious on floors. Floor substrates flex under load. Standard cementitious grout can't handle that movement. Use flexible grout on every floor, no exceptions.