Mapei Ultraflex LHT Mortar

Mapei Ultraflex LHT is a nonsag, large-and-heavy-tile mortar and thin-set mortar for large-format and heavy tile and stone for interior and exterior installations on floors, walls, and countertops. It's built for the oversized porcelain slabs, thick natural stone, and heavy-ribbed-back tile that standard thin-sets can't reliably support. 

Ultraflex LHT is designed for use at up to 1/2" (12 mm) embedded thickness to give better support under large-format tile, and is formulated with Easy Glide Technology for smooth, easy application with excellent adhesion to both substrate and tile. The polymer-enriched formula delivers high performance, and the nonsag characteristic makes it equally reliable for large tile on vertical wall surfaces. 

Open time is 30 minutes with a pot life of over 2 hours, giving installers plenty of working time on large floors and complex layouts. Zero VOC content makes it suitable for occupied interior environments. Available in gray and white — use white under light-colored stone and translucent tile. 

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What makes Ultraflex LHT different from a standard thin-set? It's specifically engineered for large-format and heavy tile — the nonsag, nonslump formula holds oversized tile in place during installation, and the 1/2" maximum embedded thickness gives large tiles the full back support they need to prevent cracking.

Can it be used on walls with large-format tile? Yes. The nonsag formula keeps heavy tile from sliding on vertical surfaces during installation — one of the key limitations of standard mortars on large wall tile.

What tile types is it compatible with? Porcelain, natural stone, heavy-ribbed-back tile, brick pavers, dimensional tile, and large-format tile of all types. For light-colored or translucent stone, use the white version.

Is it approved for use over plywood? Yes — approved for plywood underlayments meeting APA classification standards.

How long before I can grout? 8–16 hours on walls, 24 hours on floors under standard conditions.

Is it zero-VOC? Yes — 0 g/L VOC, suitable for occupied interiors including schools and healthcare facilities.

Which color should I use — gray or white? White under light-colored stone, translucent marble, or any tile where gray mortar could show through joints. Gray for everything else.

What ANSI standards does it meet? Exceeds ANSI A118.4 (polymer-modified mortar) and ANSI A118.11 (polymer-modified mortar for plywood).