Custom CustomBlend LHT Large & Heavy Tile Mortar

Custom Building Products
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Custom CustomBlend LHT Large & Heavy Tile Mortar

CustomBlend LHT Large and Heavy Tile Mortar offers a non-sag and non-slump solution for most interior and exterior, wall and floor applications. This polymer modified mortar can be applied ¾” (19mm) thick on horizontal surfaces and can be used for large format porcelain, ceramic and natural stone tile. CustomBlend LHT meets ANSI A118.4HT and A118.11.

  • For most standard floor and wall installations
  • Supports large and heavy tile for flat, even installations
  • For use with in-floor heating systems


Coverage Chart


Chart for estimating purposes. Coverage may vary based on installation practices and jobsite conditions. For more trowel sizes, please use the material calculator at or contact CUSTOM Technical Services at (800)282-8786.

Trowel Size

Min Coverage

Max Coverage

1/4" x 1/4" x 1/4" (6 x 6 x 6 mm) Square-Notch

75 ft² (6.9 M²)

86 ft² (7.99 M²)

1/4" x 3/8" x 1/4" (6 x 9.5 x 6 mm) Square-Notch

53 ft² (4.9 M²)

62 ft² (5.76 M²)

1/2" x 1/2" x 1/2" (13 x 13 x 13 mm) Square-Notch


37 ft² (3.4 M²)


43 ft² (3.99 M²)

3/4" × 9/16" × 3/8" (19 × 14 × 9.5 mm) U- Notch @450 angle

3/4" × 9/16" × 3/8" (19 × 14 × 9.5 mm) U- Notch @300 angle

30 ft² (2.8 M²)

37 ft² (3.4 M²)

33 ft² (3.1 M²)

43 ft² (3.99 M²)


*IMPORTANT NOTE: Custom Building Products does not recommend the use of a 1/2" x 1/2" x 1/2" (13 x 13 x 13 mm) Square-Notched trowel as the ½” spacing between each square notch has been shown to make it more difficult to bed tiles and achieve proper mortar coverage. CUSTOM recommends the use of a trowel design that promotes mortar ridge collapse such as either a deeper, slanted, U-notch, V-notch, or ridged large format trowel when applying thicker amounts of mortar to accommodate tile warpage and back pattern recesses. Applying mortar using a 3/4" × 9/16" × 3/8" (19mm × 14mm × 9.5 mm) U- Notch at a 300 angle provides better coverage between the tile and the substrate and the same coverage area as a ½” notched trowel.

Regardless of the trowel used, mortar coverage between the substrate and tile underside is required to be ≥80% for dry areas and ≥95% for wet areas and exteriors with all tile edges properly supported with mortar and in a minimum of 3/32” (2.38 mm) and a maximum of ¾” (19mm) continuous thickness. Note: Larger tiles, tiles with deep underside patterns and ungauged natural stone tiles may require larger notch sizes and may need to be flat back-troweled (formerly back buttered) or notched-back troweled to achieve proper coverage and mortar support. To meet warranty requirements, CUSTOM recommends testing to confirm adequate bonding mortar coverage.

When back troweling, consider the tile’s underside pattern and depth to estimate thickness and usage to add to your estimate.

Technical Data Sheet

Safety Data Sheet