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FIRM-FILL® High Strength | | Floor Underlayment

FIRM-FILL® High Strength | | Floor Underlayment

FIRM-FILL® High Strength floor underlayment is the economical solution to correct concrete problems. It resurfaces any cracked or damaged concrete to better than new, providing surface hardness from 2500 to over 3800 psi. From feather edge to 3-1/2 inches in thickness, FIRM-FILL® High Strength floor underlayment provides a durable, flat floor for virtually any finished floor covering.

Recommended For

  • Concrete Toppings & Self-Levelers:Cracked or damaged concrete, pre-cast concrete, & cast-in-place concrete.

Features & Benefits

  • Corrects cracked or damaged concrete, creating a new, flat surface
  • Can be installed from feather edge to 3-1/2 inches in thickness
  • FIRM-FILL® High Strength floor underlayment has compressive strengths from 2500 - 3800 psi
  • Rapid installation; up to 25,000 square feet installed per day
  • Quick drying; can be walked on in 90 minutes
  • Expert application; installed only by trained, Licensed Applicators
  • FIRM-FILL® High Strength floor underlayment has approvals from ICC-ES and HUD
  • Meets ASTM F2419, Standard Practice for the Installation of Thick Poured Gypsum Concrete Underlayments and the Preparation of the Surface to Receive Resilient Flooring
Specification
  • Technical DataPropertiesASTM
    Weight7.7 lbs/ft2 at 3/4" (19 mm)C472M
    ThicknessFeather edge to 3 1/2" (89mm)
    Compressive Strength2500 - 3800 psiC472M
    Thermal PerformanceK-value of 3.34 Btu/ft2·h·°F; R-value of 0.30 ft2·h·°F/BtuC177
    Fire Hazard ClassificationFlamespread index 0; Fuel Contribution 0; Smoke Density 0E84
    Patty Size7 1/2" (191mm) to 9” (229mm) plus or minus 1/2" (13mm) in diameter
    Sand1/8" (3mm) or less washed plaster, masonry sand or silica sandE11
    UL listingsListed in over 100 1, 2, 3 and 4 hour floor/ceiling assemblies


Technical specification
  • Unique ref.firm-fill-high-strength
  • Product familyGypsum Cement Underlayment
  • Product groupGypsum Concrete Floor Underlayment
  • TypeObject (single object)
  • Date of publishing2026-03-02
  • Edition number1
Classification
  • BIMobject CategoryFlooring - Underlay
  • CSI MasterFormat 2014 Code03 54 13
  • CSI MasterFormat 2014 TitleGypsum Cement Underlayment
  • OmniClass Number23-15 17 11 13
  • OmniClass TitleFloor Underlayments

Region availability

North America
Anguilla
Antigua and Barbuda
Aruba
Barbados
Belize
Bermuda
British Virgin Islands
Canada
Caribbean Netherlands
Cayman Islands
Collectivity of Saint Martin
Costa Rica
Cuba
Curaçao
Dominica
Dominican Republic
El Salvador
Greenland
Grenada
Guadeloupe
Guatemala
Haiti
Honduras
Jamaica
Martinique
Mexico
Montserrat
Nicaragua
Panama
Puerto Rico
Saint Kitts and Nevis
Saint Lucia
Saint Pierre and Miquelon
Saint Vincent and the Grenadines
Saint-Barthélemy
Sint Maarten
The Bahamas
Trinidad and Tobago
Turks and Caicos Islands
U.S. Virgin Islands
United States
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