Grout is the part of a tiling job that most people underestimate. It's also the part that fails most visibly — cracking lines, dark stains, discolouring grout that makes an otherwise nice bathroom look dirty.
I've re-grouted enough jobs to know what goes wrong. This guide will make sure you choose the right grout for your situation the first time.
The Types of Tile Grout
1. Cement-Based Grout (Most Common)
Cement-based grout is what most people mean when they say "grout." It comes as a powder that you mix with water. It's the most widely used and suitable for the majority of domestic tiling jobs.
Unsanded / Wall grout — fine-grain, smooth. For joints up to 3mm. This is what you use on wall tiles and narrow-jointed floor tiles. Sanded particles would scratch polished tiles.
Sanded / Floor grout — contains fine sand for added strength. For joints 3mm and above. The sand gives it compressive strength to handle foot traffic.
Wide-joint grout — coarser sand particles for joints over 6mm. Used for rustic tiles, reclaimed tiles, or any tile with significant size variation.
2. Epoxy Grout
Two-part product (resin + hardener) mixed on site. Much harder than cement grout — virtually impervious to staining, chemical cleaning, and moisture once cured.
Advantages:
- Near-total stain resistance (coffee, wine, grease won't penetrate)
- Excellent for very narrow joints (1.5mm) — doesn't shrink or crack
- Ideal for commercial kitchens, wet rooms, and areas exposed to harsh cleaning agents
- Colour consistency stays excellent over years
Disadvantages:
- More expensive (typically 3–4× cost of cement grout)
- Harder to work with — short working time, must be cleaned off immediately
- Not DIY-friendly on large areas without practice
When to use epoxy: narrow joints (1.5mm or less), wet rooms, commercial kitchens, anywhere that will be cleaned frequently with strong products.
3. Silicone (Not Technically Grout)
Used for movement joints — the perimeter gap around a tiled floor, changes of plane (where floor meets wall), and around baths/shower trays. Silicone is not grout and cannot be used in grout joints. However, it's often confused with grout because it fills gaps between tiles in certain locations.
Use silicone in any joint that will need to accommodate movement. Grout at these points will crack — sometimes within weeks.
Which Grout for Each Application
Bathroom Wall Tiles
Use: Unsanded cement grout (joints up to 3mm) or fine-grain grout
Standard bathroom wall tiles (200×300mm, 300×600mm, metro tiles) with 2–3mm joints suit an unsanded grout. Choose a colour that complements your tiles — most manufacturers offer 20+ colour options.
Brand recommendation: Mapei Ultracolor Plus, BAL Micromax 2, Ardex Fugabella
Bathroom Floor Tiles
Use: Sanded floor grout with 3mm+ joints; fine-grain or epoxy for 1.5–2mm joints on large format
For standard floor tiles with 3mm joints, use a sanded floor grout with good moisture resistance. In a bathroom, use a grout with added anti-mould or biocide protection.
For large format rectified tiles with 1.5mm joints, unsanded or epoxy grout. The fine particles of unsanded grout fill narrow joints cleanly; sanded grout won't compress into a 1.5mm gap properly.
Wet Room / Walk-In Shower
Use: Epoxy grout or premium cement grout with waterproof additive
A wet room is the highest-demand environment for grout. The grout is wet every time the shower is used. Cheap cement grout will stain, darken, and eventually allow water penetration behind the tiles.
My recommendation: epoxy grout for the shower floor and lower 600mm of walls. Premium cement grout with a waterproof additive or sealant for the upper walls.
Kitchen Splashback
Use: Unsanded or fine-grain cement grout; epoxy if the splashback is directly above the hob
For a kitchen splashback away from the hob, a standard fine-grain grout is fine. Seal it after installation and it'll stay clean.
For splashbacks directly above the hob (exposed to grease, steam, and temperature variation), use epoxy grout — the stain resistance makes a material difference over the years.
External Tiles (Patios, Garden Walls)
Use: Frost-resistant outdoor grout
External tiles require a grout formulated to withstand freeze-thaw cycling. Standard indoor grout will fail outside — it absorbs water, freezes, expands, and cracks.
Look for products labelled "frost-resistant" or "exterior use." Use wider joints (5–8mm) on external work to accommodate thermal movement.
Grout Joint Width: What the Rules Say
| Joint Width | Grout Type | |---|---| | 1.5mm | Epoxy or unsanded | | 2mm | Unsanded or fine-grain cement | | 3mm | Unsanded or fine-grain cement | | 4–6mm | Sanded cement | | 6mm+ | Wide-joint / coarse-grain cement |
The joint width is typically set by the tile type and manufacturer recommendation. Rectified tiles (ground to precise dimensions) can use very narrow joints. Non-rectified tiles have more size variation and need wider joints to absorb that variation.
How to Choose Grout Colour
This is surprisingly important. Grout makes up 8–15% of the visible tile surface on a standard installation (more with wide joints or mosaic). The wrong colour will significantly affect how the finished room looks.
Matching grout: Same colour family as the tile. Creates a seamless, monolithic look. Popular with large format and neutral tiles.
Contrasting grout: Deliberately different colour. Creates a grid pattern that accentuates the tile layout. Popular with metro tiles and geometric patterns.
White or light grout in wet areas: Avoid unless you seal it. Light grout stains easily in wet rooms.
Dark grout: Excellent for wet rooms — staining is less visible. Looks dramatic but shows limescale deposits more.
My most-used colours professionally: mid-grey for most contemporary bathrooms, charcoal for darker tiles, warm beige for natural stone looks.
Sealing Grout
Cement-based grout is porous. It will absorb moisture, grease, and cleaning products over time. Sealing significantly extends its clean appearance and makes it easier to maintain.
Seal: All cement grout in wet rooms, kitchen splashbacks, and floor tiles.
Don't need to seal: Epoxy grout (non-porous), or grout in very low-traffic dry areas.
Apply a penetrating grout sealer with a small brush or applicator after the grout has fully cured (minimum 72 hours for cement grout). Mapei Grout Sealer and BAL Microguard are widely available and straightforward to apply.
FAQ
How long before I can get grout wet? Most cement grouts need 24–72 hours before getting wet. Epoxy grouts are generally water-resistant within 24 hours. Check the manufacturer's data sheet — this varies by product.
Can I grout over old grout? No. New grout applied over old grout won't bond properly. Rake out the old grout first using a grout rake (available for £10–15 from most tile shops) and then apply fresh grout. Going over old grout is a bodge that will fail within months.
My grout is cracking — what went wrong? Most common causes: adhesive not fully cured before grouting, movement joint filled with grout instead of silicone, or wrong grout type (rigid grout on a substrate with movement). See our full guide to subfloor preparation for the foundation causes.
Why does my white grout go yellow? Cleaning products (especially those containing bleach) can discolour white cement grout over time. Use pH-neutral tile cleaners. If you have white grout in a shower, seal it and clean with a mild solution only.
Is epoxy grout worth it? For wet rooms and kitchen hobs — yes. The stain resistance and longevity justify the extra cost. For a dry bathroom wall with standard tiles — probably not necessary unless you want the narrow joint aesthetic.
Grout Application Tools
- Rubber float — for pressing grout into joints and cleaning off excess
- Grout sponge — for cleaning
- Grout sealer applicator — for sealing after installation
All professional tiling tools available in our shop.