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Premium, Rapid Setting, Polyer Modified Lht Mortar

SikaTile®-425 LHT Secure Set Rapid is a premium-grade, single-component, high-performance, polymer-modified, rapid-setting large and heavy tile mortar for interior and exterior installations of tile. This mortar has a high content of unique dry polymer, resulting in excellent adhesion to the substrate and tile.  SikaTile®-425 LHT Secure Set Rapid is a fast setting product, allowing grouting in 3 hours and open for traffic in 4 – 6 hours.
  • For use with ceramic tile, porcelain tile, and natural stone 
  • Ideal for time critical residential and commercial applications 
  • Superior flexibility, high strength, with rapid set time 


SikaTile®-425 LHT Secure Set Rapid supports large and heavy tile for flat, even installations and is suitable for bonding the following types of tile and stone:
  • Brick and thin brick
  • Cement-based precast terrazzo
  • Impervious porcelain and glass tile
  • Natural stone tile
  • Vitreous, semi-vitreous or non-vitreous tile:
    • Ceramic, mosaic, quarry, cement body tile
  SikaTile®-425 LHT Secure Set Rapid can be installed in most interior and exterior residential and commercial installations on floors and walls on the following recommended substrates:
  • Brick Masonry
  • Cement Backer Board1
  • Cement Mortar Beds
  • Cement Plaster
  • Cement Terrazzo
  • Ceramic Tile and Stone
  • Concrete
  • Concrete Masonry
  • Exterior Grade Plywood2
  • Gypsum Wallboard2
  • SikaLevel®
  • SikaTile® Membranes
  • Approved SikaLastic® Under Tile Waterproofing
1 Consult cement backer board manufacturer for installation recommendations and to verify acceptability for exterior use.
2 Interior Use Only.


  • For use with ceramic tile, porcelain tile, and natural stone 
  • Ideal for time critical residential and commercial applications 
  • Superior flexibility, high strength, with rapid set time 
  • Allows for grouting in 3 hours and open for traffic in 4 – 6 hours 
  • For use with large and heavy tile and natural stone
  • Rapid setting formula
  • Non-slumping/non-shrinking formula eliminates tile lippage
  • May be applied up to 3/4" (19 mm) thick on horizontal applications
  • For interior and exterior floors and walls
  • Mold and mildew resistant


25 lb. (11.34 kg.) bag

Product Information

Chemical Base

Portland cement, selected aggregates, water retention additives, re-dispersible polymer

Shelf Life

6 months from date of production when stored in original, sealed package

Storage Conditions

Store in undamaged, original, sealed package, in dry conditions at 73⁰ F (23⁰ C)


Gray and White

Sika® is committed to environmental responsibility in both products produced and in manufacturing practices. Complete the LEED Product Data Request Form for detailed information based on project location. Use of this product can contribute towards LEED® v3 certification:

  • Up to 2 points towards MR Credit 5, Regional Materials
  • Up to 1 point towards IEQ Credit 4.1, Low-Emitting Materials – Adhesives & Sealants 


American National Standards Institute (ANSI) — ANSI A108.5, A118.4F and A118.11 of the American National Standards for the Installation of Ceramic Tile ASTM International (ASTM) 

  • ASTM C109 Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2” or 50mm Cube Specimens) 
  • Resilient Floor Covering Institute - (RFCI) Recommended Work Practices for Removal of Resilient Floor Coverings 
  • Tile Council of North America (TCNA) - TCNA Handbook for Ceramic Tile Installation, TCNA EJ171 Movement Joint Guidelines. 
  • ISO 13007-2 C2FP1

Application Information

Mixing Ratio

2.5 quarts (2.4 liters) of clean potable water per 25 lb. bag

Pot Life

45 Minutes*

Open Time

10 - 20 minutes*

Cure Time

Allow 2-3* hours before grouting, 4 hours before opening to light traffic and protect from heavy or vehicular traffic for 24 hours

* Pot life, open time, and time before grouting vary based on ambient temperatures and jobsite conditions.

Applied Product Ready for Use

Grouting may begin 2 to 3 hours after installation of tile, or once tile has reached a firm set.  Product curing time is affected by ambient and surface temperatures and humidity. Allow at least 4 hours before opening to light traffic and protect from heavy or vehicular traffic for 24 hours. As necessary, use plywood or other load distributing protection when moving heavy equipment across tiled assembly. 


In a clean container, add approximately 2.5 quarts (2.4 liters) of clean potable water, then add the contents of the 25 lb. (11.34 kg) SikaTile®-425 LHT Secure Set Rapid mortar. Mix thoroughly by hand or with a slow speed mixer to a smooth, thick, trowelable consistency. No need to slake, once mixed the product is ready to use. Mortar consistency shall be such that when applied with the recommended notched trowel to the substrate, the ridges formed in the mortar do not flow or slump. During use, stir mortar mix occasionally. Do not add additional water. Do not add latex liquid additives to SikaTile®-425 LHT Secure Set Rapid.


Read all installation instructions before installation. Choose a notched trowel with sufficient depth to achieve more than 80% mortar coverage and transfer to substrate and back of tile to both the tile and substrate for all interior applications, and more than 95% for exterior, commercial floor and wet applications, back-butter the tile to meet these requirements. With pressure, apply a coat of mortar by using the flat side of the trowel to key the mortar into the substrate. With the notched side of the trowel, apply additional mortar by combing it in a single direction parallel to the shortest dimension of the tile. Spread only as much mortar as can be tiled before the product skins over. Open time can vary with jobsite conditions. Set tiles firmly into the wet mortar and push the tiles back and forth in a direction perpendicular to trowel lines to collapse the mortar ridges and to help achieve maximum coverage. 

All expansion, control, construction, cold, saw-cut, isolation, contraction, and seismic joints in the structure should continue through the tilework, including such joints at vertical surfaces, as specified per TCNA Method EJ171 or TTMAC Specification Guide 09 30 00, Detail 301MJ. Do not cover movement joints with mortar.

ISO 13007 Classification

Classification Code

Classification Requirement


C2 (cementitious, improved adhesion)

≥ 145 psi (1 MPa) after standard aging. Heat aging, water immersion and freeze/thaw cycles


F (fast setting adhesive)

≥ 72.5 psi (0.5 MPa) for tensile adhesion strength after 6 hours, and open time after 10 min 


P1 (normal adhesion to plywood)

≥ 72.5 psi (0.5 MPa)