Premium gypsum cement, GSL® M3.4 is an exciting, unique product for creating a self-leveling underlayment for use over virtually all interior surfaces.

Pumpable, GSL delivers high strength, good water resistance and outstanding adhesion. Applications from nearly a featheredge up to 3” depth can be achieved in a single pour. GSL remains owable for nearly an hour, yet will withstand foot traf c at any depth in about two hours. This product offers high density, yet less nished weight and more exibility than Portland cement self-levelers.

GSL is designed for installation by trained contractors from DEPENDABLE, LLC. Please consult with a local representative for a list of contractors in a specific geography. Features and Benefits

  • Provides additional protection for fire resistance as shown in UL approved assemblies
  • Provides additional sound control enhancements as tested under ASTM E90, Airborne Noise or STC and ASTC
  • Covers virtually any surface (especially plywood and OSB subfloors)
  • Durable High Strength Gypsum
  • Outstanding heal that provides a smooth, dense surface
  • Open time up to 60 minutes
  • Non-Alkaline—adhesive friendly
  • Thickest single pour—3 inches
  • Withstands construction but should be protected when exposed to trade traffic
  • As little as 3/8” coverage over other surfaces


  • Multi-family
  • Renovations
  • Floor leveling
  • Light commercial
  • Commercial/retail/office
  • Hotel/motel
  • For sound and fire control applications

GSL® M3.4

  • 80 lb. (36 kg.) Bag, valve double wall bag


• Building must be fully enclosed including windows and roof.
• Temperature must be 45ºF and rising and maintain “a minimum of” 45ºF temperature for a minimum of 4 to 5 days after installation.
• Subfloor must be a minimum of L/360 and broom swept with all excess wall board mud removed, all holes patched.
• Wood construction must be with tongue and groove subfloor (OSB or plywood).
• Adequate drying must be maintained until the moisture in the gypsum has been allowed to evaporate. This requirement is typically a minimum of 5 to 7 days but   may be longer depending on humidity conditions in the local environment.
• For installation on concrete substrates the subfloor must be fully cured (typically 28 days). Moisture tests should be performed to assure proper hydration under ASTM F1869 to assure MVE level is less than 3.0 lb. per 1000 square feet.
• For below grade applications or over crawl space in residential, vapor barriers must be applied.


Subfloor must be properly primed. Use DEPENDABLE PRIMER SL on all surfaces. All supporting surfaces shall be structurally sound, solid, free of movement and well bonded. They shall be free of dust, oil, grease, tar or other contaminants that may act as a bond breaker. Deflection cannot exceed L/360.


Using a long handle roller, soft bristle broom or brush, apply DEPENDABLE PRIMER SL at full strength (Do NOT Dilute). Ensure a complete and uniform coverage. Allow to become very tacky or dry (about 1 hour). Mixing Follow DEPENDABLE, LLC guidelines and use only with trained installers of GSL


Follow DEPENDABLE, LLC guidelines and use only with trained installers of GSL (Please refer to Data Sheet for MIXING INSTRUCTIONS)

Strength Ratio: 3200 – 4500 psi

Substrate: Plywood, OSB, concrete and approved acoustical treatment are acceptable. Wood material must be of proper thickness, tongue and groove construction and properly fastened. Concrete should be clean, dry and free of obvious structural problems. All substrates must be properly sealed and primed before the GSL floor underlayment is applied.

Storage: Material should be kept in a dry area. Avoid ambient temperature below 40° F and above 110° F for prolonged periods. Shelf-life of six months.


 Multiple lifts: Multiple lifts does not require a primer with GSL. Second lift can be accomplished upon an initial set that can handle the load of the hose operator and finisher.

NOTE: Temperature and humidity levels affect the drying characteristics of GSL. However, unlike Portland cement materials, GSL may be force dried with the use of heat or fans once set.



For Interior use only.
Do not use…

– Where hydrostatic pressure (water) is present or moisture emissions exceeds level permitted for installed floor covering.
– Where surface or ambient temperature falls to or below 45°F 72 hours before or after installation.
– As a trowelled patch or at less than natural minimum flow thickness.
– Exterior, exposed applications or as a wear surface.

• GSL is NOT a wear surface.
• DO NOT INSTALL WITHOUT TONGUE AND GROOVE SUBFLOOR unless utilizing back bracing or filling all joints.
• CHECK JOIST DEFLECTION and assure performance greater than L/360
• ASSURE BUILDING IS COMPLETE ENCLOSED including windows and roof.
• PROVIDE VENTILATION after placement of GSL.