How to use SUMO S03 Tile & Stone Adhesive (large-format & heavy stone)

Large tiles need a flat, sound base — they won't bridge a wavy floor. Check flatness with a long straightedge (a common tolerance is ~3 mm under 2 m); where it dips or humps, level it first with SUMO Floorscreed and let it cure. The surface must be fully cured, clean and free from dust, grease and curing compounds.

Vacuum all dust; dampen highly absorbent surfaces and drain the excess. Dry-lay slabs, plan the layout and snap chalk lines. Plan movement joints — at the perimeter and breaking up large fields — before you start.

Pour two-thirds of the water in, add the powder slowly on low speed, add the remaining third, and mix to a smooth, lump-free paste that holds a ridge. Rest 2–3 minutes, then re-stir. Mix batches sized to the (extended) open time.

Key a firm skim onto the base with the flat trowel, then comb a deep ribbed bed with a 12 mm notch or half-trowel, in straight lines one direction. The extended open time lets you comb a larger area — but check it hasn't skinned before you place.

Skim a tight, full coat of adhesive across the back of the slab as well. Back-buttering fills the tile's bow and keyed back so you achieve a solid, void-free bed — non-negotiable for large formats, heavy stone and exteriors.

Lift the slab (use suction lifters), lower it onto the ridges just off position, then slide it a few millimetres across the ridges to collapse them. Bed it down evenly using a rubber mallet and a beating block so you don't crack the tile or create lippage.

Fit tile levelling clips on all sides and run a long straightedge across adjacent tiles to eliminate lippage while the bed is fresh. Large formats show the smallest step, so take the time to get them dead flat.

Lift an early slab and confirm the adhesive covers 95% or more of the back with solid corners — for large-format and exterior work full contact is essential. If not, comb deeper and butter more, then re-check.

Keep the planned movement joints open (don't fill them with adhesive) and clean adhesive off the faces and out of the tile joints before it sets. Wash tools immediately.

Let the adhesive cure (about 24 hours, longer for big beds and cool weather) before grouting. Grout the tile joints with SUMO Sumoxy epoxy grout (2-Part, or 3-Part for larger joints) — waterproof and stain-free — fill the movement joints with a flexible sealant (not rigid grout), and cure the finished surface.