FIRM-FILL® 3310
An innovative product that elevates gypsum concretes to an unprecedented level of unyielding performance. FIRM-FILL® 3310 floor underlayment's fast-setting surface rapidly eliminates water allowing for accelerated drying time and unparalleled levels of strength and finish over wood and concrete subfloors in new construction and renovation projects.
Recommended For
![]() |
Multi-Family Application / MarketMulti-family, custom homes, commercial buildings, hotels & motels, & renovation projects. |
Features & Benefits
- Premium strength, smooth surface over wood and concrete subfloors
- Eliminates water rapidly for accelerated drying time
- FIRM-FILL® 3310 floor underlayment can be poured before or after drywall
- Exceptional compressive strengths from 2000 to 3300 psi
- Delivers fire resistance and improved sound performance
- FIRM-FILL® 3310 floor underlayment creates a smooth, crack-resistant surface
- Expert application; installed only by trained, Licensed Applicators
- Meets ASTM F2419, Standard Practice for the Installation of Thick Poured Gypsum Concrete Underlayments and the Preparation of the Surface to Receive Resilient Flooring
External Resources

Product Resources
Technical Data |
Properties |
ASTM |
Weight | 7.6 lbs/ft2 at 3/4" (19 mm) | C472M |
Thickness | 3/4" (19mm) (minimum over wood) to 3 1/2" (89mm); 1/2" (13mm) (minimum over concrete) | |
Compressive Strength | 2000 - 3300 psi | C472M |
Thermal Performance | K-value of 2.8 Btu/ft2·h·°F; R-value of 0.36 ft2·h·°F/Btu | C177 |
Fire Hazard Classification | Flamespread index 0; Fuel Contribution 0; Smoke Density 0 | E84, E136 |
Patty Size | 8 1/2" (approx. 216mm) plus or minus 1/2" (13mm) in diameter | |
Sand | 1/8" (3mm) or less washed plaster or masonry sand | E11 |
UL listings | Listed in over 100 1, 2, 3, and 4-hour floor/ceiling assemblies |