Question 1

How much tile adhesive do I need per square metre?

Accepted Answer

Typical coverage rates: walls with standard tiles (up to 300x300 mm) using a 6 mm notch trowel need about 2-3 kg/m². Floors with larger tiles (300x300 to 600x600 mm) using a 10-12 mm notch trowel need about 4-6 kg/m². Large format tiles (600x600 mm+) may need back-buttering, which adds 1-2 kg/m². Always check the manufacturer coverage rate for the specific product.

Question 2

What notch trowel size should I use?

Accepted Answer

The trowel notch size depends on tile size: 6 mm for tiles up to 200x200 mm (small wall tiles), 10 mm for tiles 200-400 mm (standard floor tiles), and 12 mm for tiles over 400 mm (large format). For very large tiles (600x600+), some installers use a 12 mm or 15 mm trowel plus back-buttering. The goal is to achieve minimum 95% coverage on floors and wet areas, and 80% on dry walls.

Question 3

What type of tile adhesive should I use?

Accepted Answer

Flexible adhesive (S1 or S2 class per BS EN 12004) for underfloor heating, timber substrates, large format tiles, and anywhere subject to movement or vibration. Rapid-set for quick turnaround jobs (walkable in 2-3 hours). White adhesive for translucent or light-coloured tiles. Standard grey for most floor and wall applications. Thick-bed adhesive for correcting minor substrate irregularities up to 12-15 mm.

Question 4

Do I need to back-butter large tiles?

Accepted Answer

Yes, for tiles over 400 x 400 mm and all natural stone tiles, back-buttering (applying a thin skim of adhesive to the back of the tile as well as the substrate) is recommended to achieve the required coverage. BS 5385 recommends a minimum 95% adhesive coverage for floor tiles and wet areas. Air pockets under large tiles cause cracking and loose tiles.

Notch Size (mm)	Bed Thickness (mm)	Coverage (kg/m²)	Suitable Tile Size
4	~2	1.5–2.0	Mosaics, small tiles (up to 100 mm)
6	~3	2.0–3.0	Wall tiles up to 300 x 300 mm
8	~4	3.0–4.0	Floor tiles 200–400 mm
10	~5	4.0–5.0	Floor tiles 300–600 mm
12	~6	5.0–6.5	Large format 600 mm+
15	~7.5	6.0–8.0	Very large format, natural stone

Class	Type	Use	Open Time
C1	Standard cementitious	Internal walls, dry floors	~20 mins
C2	Improved cementitious	Floors, wet areas, external	~20 mins
C2 S1	Flexible (deformable)	UFH, timber substrates, large tiles	~20 mins
C2 S2	Highly flexible	High movement, external, heated floors	~20 mins
C2 F (rapid)	Fast-set cementitious	Quick turnaround, commercial	~10 mins
D1 / D2	Ready-mixed (dispersion)	Internal walls only (not floors)	Variable

Bag Size (kg)	6 mm Trowel (m²)	10 mm Trowel (m²)	12 mm Trowel (m²)
10	3–5	2–2.5	1.5–2
20	7–10	4–5	3–4

UK Tile Adhesive Coverage Rates

Adhesive Coverage by Trowel Size

Adhesive Types (BS EN 12004)

Coverage Per Bag

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