Question 1

How much grout do I need per square metre?

Accepted Answer

It depends on the tile size, joint width and tile thickness. Small tiles (100x100 mm) with 3 mm joints need approximately 1.5-2.0 kg/m². Large tiles (600x600 mm) with 3 mm joints need only about 0.3-0.5 kg/m². Wider joints dramatically increase consumption — doubling the joint width roughly doubles the grout needed. Natural stone with wide joints (5-10 mm) can use 2-5+ kg/m².

Question 2

What width grout joint should I use?

Accepted Answer

For rectified (precision cut) porcelain tiles, joints as narrow as 1.5-2 mm are possible. For standard ceramic wall tiles, 2-3 mm is typical. For floor tiles, 3-5 mm is standard. For natural stone, 5-10 mm is common. Very large format tiles often use 2-3 mm joints. Always follow the tile manufacturer recommendation — joints too narrow can crack, and some tiles require wider joints to accommodate size variation.

Question 3

What is the difference between sanded and unsanded grout?

Accepted Answer

Sanded grout contains fine sand and is used for joints 3 mm and wider — the sand provides bulk and prevents cracking in wider joints. Unsanded grout is smoother and used for joints under 3 mm and for polished or scratch-sensitive tiles (marble, polished porcelain). Epoxy grout is stain-proof and waterproof but more expensive and harder to work — ideal for wet areas, commercial kitchens and areas needing chemical resistance.

Question 4

How do I calculate grout quantity?

Accepted Answer

Formula: kg/m² = (joint width x tile depth x (tile length + tile width)) / (tile length x tile width) x grout density (typically ~1.6 kg/litre). All measurements in mm, result in kg/m². For example: 300x300 mm tiles, 8 mm thick, 3 mm joints = (3 x 8 x 600) / (300 x 300) x 1.6 = 0.26 kg/m². Add 10-15% for waste.

Tile Size (mm)	2 mm joint	3 mm joint	5 mm joint	10 mm joint
100 x 100	0.51	0.77	1.28	2.56
150 x 150	0.34	0.51	0.85	1.71
200 x 200	0.26	0.38	0.64	1.28
250 x 250	0.20	0.31	0.51	1.02
300 x 300	0.17	0.26	0.43	0.85
300 x 600	0.13	0.19	0.32	0.64
400 x 400	0.13	0.19	0.32	0.64
450 x 450	0.11	0.17	0.28	0.57
500 x 500	0.10	0.15	0.26	0.51
600 x 600	0.09	0.13	0.21	0.43

Type	Joint Width (mm)	Key Properties	Best For
Unsanded cementitious	1–3	Smooth finish, non-scratching	Polished tiles, narrow joints, walls
Sanded cementitious	3–15	Strong, bulk fill, textured	Floors, wide joints, natural stone
Flexible cementitious	2–10	Movement accommodation	UFH, timber substrates, large tiles
Epoxy	1–15	Stain-proof, waterproof, chemical resistant	Wet rooms, commercial kitchens, pools
Resin	1–6	Flexible, water-resistant	Bathrooms, splashbacks

Bag Size (kg)	300x300 tiles, 3 mm joints (m²)	600x600 tiles, 3 mm joints (m²)
2.5	~9	~19
5	~19	~38
10	~38	~77

UK Grout Coverage Rates by Tile Size

Grout Coverage Table (kg/m²)

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