ARDEX S 21 Rapid Setting Floor Tile Bedding Mortar

For solid bed fixing of large format tiles and natural stone – walk on and grout after just 3 hours.

ARDEX S 21 is a high-performance, rapid-setting and hardening floor tile bedding mortar formulated for solid bed fixing of large format tiles, brick pavers, and natural stone. Its pourable consistency allows for effortless solid bedding without voids, while the fast-curing formula enables grouting and light foot traffic after only 3 hours. ARDEX S 21 can also be mixed with sharp sand to form ramps, falls, or pre-level subfloors, making it an exceptionally versatile solution for internal and external installations.

Key Features & Benefits

• Rapid setting and hardening: Walk on and grout tiles after 3 hours.
• Ideal for large format tiles, pavers, and non-moisture-sensitive natural stone.
• Pourable, solid-bed consistency for full coverage without voids.
• Use with sharp sand to form ramps and pre-level uneven floors.
• Internal and external use including swimming pools and wet areas.
• Suitable with under-tile heating systems when used with ARDEX E 90 Mortar Admix.
• Grey colour – ideal for general floor installations.
• Low embodied carbon: 0.49 kg CO₂ eq/kg (A1–A3 production stage).

Ideal Applications

ARDEX S 21 is designed for a wide range of floor tiling projects in both residential and commercial environments, including:

• Fixing large format ceramic, porcelain, and natural stone floor tiles.
• Installing brick pavers and terrazzo tiles.
• Creating ramps, slopes, and pre-levelled subfloors with the addition of sharp sand.
• Internal and external areas, including wet rooms, swimming pools, and balconies.

Technical Data

Mixing Instructions

Add ARDEX S 21 powder to clean water in a clean mixing container while stirring continuously. Mix thoroughly to achieve a pourable, workable mortar. For best results, use an ARDEX mixing paddle with a variable-speed drill.

• Mix ratio: Approx. 4½ parts powder to 1 part water.
• Water requirement: 3.5 litres of clean water per 22kg bag.
• Working time: Approx. 30 minutes at 20°C.
• For underfloor heating or additional flexibility, replace water with a mixture of 2kg ARDEX E 90 and 2 litres of water.

The consistency can be adjusted for semi-dry or fluid applications as needed.

Application

Apply ARDEX S 21 to the prepared surface using a trowel, then comb through with a suitable square-toothed notched trowel to create even ribs. Its pourable consistency allows solid bed fixing in one operation without the need for buttering, ensuring no voids beneath tiles. Tiles should be fixed within the 10-minute open time for best results.

Grouting & Curing

Tiles fixed with ARDEX S 21 can be grouted and walked on after just 3 hours at 20°C, ensuring minimal downtime and faster project turnaround.

Packaging, Coverage & Storage

• Packaging: 22kg paper sack with polyethylene liner.
• Coverage: Approximately 1.8kg/m²/mm thickness.
• Storage: Store in a cool, dry place, off the ground, and protected from moisture.
• Shelf life: 12 months from date of manufacture (unopened packaging).

Why Choose ARDEX S 21?

ARDEX S 21 Rapid Setting Bedding Mortar delivers exceptional performance for demanding floor installations. Whether fixing large porcelain tiles, forming ramps, or working in wet areas, its rapid strength development, easy mixing, and versatile consistency make it the professional’s choice for both speed and durability.

FAQs