Tiles and tiling for UK homes
How to Choose Grout for Floor and Wall Tiles
7 November 2026
To choose grout for floor and wall tiles, start with three things: the joint width, the room and how much wear and water the tiles will see. Grouts are classified under BS EN 13888. CG1 is a normal cement-based grout, CG2 is an improved one, and RG is a reaction resin grout, usually epoxy. For most homes, a cement-based grout of the right joint width does the job, with CG2 for heated screed floors and CG2 or RG for heavily used floors.
Quick answer: Match the grout to the joint width first (narrow joint grouts for joints of about 1 to 3mm, wide joint grouts above 3mm), then to the room. CG1 or CG2 cement-based grouts suit most walls and floors, CG2 is recommended for heated screed floors, and resin (RG) grouts suit areas that need chemical resistance and easy cleaning.
Key Takeaways
Grouts are classified under BS EN 13888: CG1 normal, CG2 improved, RG reaction resin.
On CG2 grouts, W means reduced water absorption and A means high abrasion resistance.
Narrow joint grouts suit joints of about 1 to 3mm, and wide joint grouts suit joints over 3mm.
BS 5385 sets minimum joint widths of 2mm or 3mm on walls, depending on tile size, and 3mm on floors.
Grout isn't waterproofing. In a shower, the waterproofing goes behind the tiles.
What the grout codes mean
BS EN 13888 gives every grout a class, and the code is printed on the bag.
Code | What it means |
|---|---|
CG1 | Normal cement-based grout |
CG2 | Improved cement-based grout, typically highly polymer modified |
W | Reduced water absorption (added to CG2) |
A | High abrasion resistance (added to CG2) |
RG | Reaction resin grout, such as epoxy |
So a bag marked CG2 WA is an improved cement-based grout with reduced water absorption and high abrasion resistance. Our guide to tile standards explains the codes on adhesive bags as well.
Start with the joint width
The Tile Association notes that narrow joint grouts are typically used for joints of 1 to 3mm, and wide joint grouts for joints over 3mm. The bag will give the range a grout is made for.
BS 5385 also sets minimum joint widths. The Tile Association's answers to common tiling questions say wall joints should be at least 2mm for tiles under 0.1 square metres with no side over 600mm, and at least 3mm for tiles from 0.1 to 1 square metre with no side over 1200mm. Floor joints should be at least 3mm.
Then match the grout to the room
The Tile Association's guidance on choosing grout gives these options for different conditions.
Where | Grout options |
|---|---|
Internal dry walls | CG1, CG2 or RG |
Internal dry floors | CG1, CG2 or RG |
Domestic showers (walls and floors) | CG1, CG2 or RG |
Heated screed floors | CG2 |
Heavily trafficked floors | CG2 or RG |
The Tile Association describes resin grouts as generally impervious to water, resistant to a wide variety of chemicals and easy to keep clean and hygienic. They need careful mixing, so follow the maker's instructions closely.
Grout and water
Grout with reduced water absorption helps, but it doesn't make a shower watertight. The Tile Association points out that BS 5385 part 4 is clear: a water-resistant adhesive and grout is no substitute for a waterproof tanking system behind the tiles. It also says to leave a newly tiled shower for at least 14 days before you use it. If you're thinking of tiling over old shower tiles, our guide on tiling over existing tiles explains when that works.
Getting an even colour
Uneven, patchy grout is a common complaint. The Tile Association says cleaning off too early can affect the colour and leave a weak, dusty surface, and that adding more water than the maker recommends can lighten the grout. Mix to the instructions and clean off when the bag says.
Before grouting, the joints should be at least 6mm deep, or the full depth of the tile if it is thinner, and free of dust. Very porous tiles and natural stone can stain from grout, so try the grout on a spare tile first. Our guide on how to seal natural stone tiles explains sealing before grouting.
Where you shouldn't use grout
Some joints need sealant, not grout. BS 5385 calls for movement joints where tiling meets baths, sinks and shower trays, around the edge of a tiled floor and, in large tiled areas, at internal corners. The Tile Association notes that movement joints in wall tiling, and those around the edge of a floor, may be filled with a suitable sealant.
If you're still choosing the tiles, our guide to porcelain or ceramic tiles explains how the two differ.
What is the difference between CG1 and CG2 grout?
CG1 is a normal cement-based grout. CG2 is an improved cement-based grout, typically highly polymer modified, and can carry extra ratings for reduced water absorption (W) and high abrasion resistance (A).
What grout should I use in a shower?
The Tile Association's guidance lists CG1, CG2 or RG for domestic showers. The grout isn't the waterproofing, though: BS 5385 part 4 calls for a waterproof system behind the tiles.
Is epoxy grout worth it?
Epoxy is a reaction resin (RG) grout. It resists a wide variety of chemicals and is easy to keep clean, so it's worth considering for kitchens and wet areas. It needs careful mixing, so follow the maker's instructions.
How wide should grout lines be?
BS 5385 sets minimums of 2mm or 3mm on walls, depending on tile size, and 3mm on floors. Choose a grout made for your joint width.