# ARDEX S 21

Tile adhesive · ARDEX

A 22 kg bag of ARDEX S 21 covers about 4 m², by ARDEX UK's own figure: “approximately 4m2 of tiles with a bed thickness of 3mm”. ARDEX UK's other figures are in the table below.
Source: ARDEX UK, ARDEX S 21 product data sheet, read 12 October 2026.

What it is for, in the maker's words: “ARDEX S 21 is a special rapid hardening pourable bedding mortar for floor tiles in internal and external locations” (ARDEX S 21 product data sheet, read 12 October 2026).

## The maker's figures

| Figure | The maker's words |
|---|---|
| about 4 m² per 22 kg bag | “approximately 4m2 of tiles with a bed thickness of 3mm” |
| about 1.8 kg a square metre for each mm of bed | “Approximately 1.8kg of powder/m2/mm” |
- The conditions the maker names: Each figure is for the notch, bed, tile or joint the maker names beside it. An uneven surface, a larger notch or buttering the backs of the tiles takes more.
- Waste: None of these figures adds anything for what is left in the bucket or spilt.

## Sizes

22 kg bag

## Where to buy it

The page has the shops' own searches for it, and any link there that is paid for is marked Ad: https://buildbatch.co.uk/products/ardex-s-21/#where-to-buy. BuildBatch sells nothing and compares no prices.

## Questions

**How much does a 22 kg bag of ARDEX S 21 cover?** ARDEX UK states about 4 m² (“approximately 4m2 of tiles with a bed thickness of 3mm”), in its ARDEX S 21 product data sheet, read 12 October 2026. Nothing is added for waste.

**What is ARDEX S 21 for?** ARDEX UK says: “ARDEX S 21 is a special rapid hardening pourable bedding mortar for floor tiles in internal and external locations” (ARDEX S 21 product data sheet, read 12 October 2026).

**What sizes does ARDEX S 21 come in?** The catalogue lists 22 kg bag. A shop may not stock every size.

## Where the figures come from

- ARDEX UK, ARDEX S 21 product data sheet (https://ardex.co.uk/wp-content/uploads/2017/06/technical-datasheet-s-21.pdf): coverage and what it is for, read 12 October 2026.

Written with AI tools; not yet checked by a tradesperson. Follow the bag's own instructions.

The page: https://buildbatch.co.uk/products/ardex-s-21/