GSL® CSD is a gypsum portland cement, designed for fire-rated corrugated steel deck construction applications. GSL® CSD is lighter and thinner than other concretes. It can be poured as thin as 1” over the top of the fluting in the corrugated deck. GSL® CSD weighs about 12.8 lbs. per square foot (over a 9/16” fluted deck).

GSL® CSD’s formula increases performance delivering you with a smoother, high compressive strength substrate suitable for a variety of floor coverings. GSL® CSD is mixed on job site with approved sands providing compressive strengths from 3000-4500 psi.

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.

  • Provides additional protection for fire resistance as shown in UL approved assemblies
  • Lighter and thinner
  • Provides smooth hard durable surface
  • High compressive strength
  • Self sealing and low porosity formulation enables direct-bonded floor coverings
  • For sheet goods, VCT, tile and stone, wood, or carpet
  • Removes weight from the construction assembly, reducing the overall cost of structural reinforcement
  • Used with a variety of floor coverings


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


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

The interior of the building must be enclosed, protected from sun and wind, and a minimum temperature of 50ºF must be maintained during the installation and for a period of seventy-two (72) hours after the installation of the GSL CSD.

The substrate must be indoor, clean, dust and contaminant free. Any loose or weak material present on substrate must be mechanically removed.

GSL CSD is highly flowable. The perimeter, mechanical and plumbing penetrations, and other gaps in the substrate must be sealed to prevent leaks. Prior to pouring GSL CSD, an approved priming system for galvanized steel must be used. Consult a Dependable technical representative on the proper priming system.


Follow DEPENDABLE, LLC guidelines and use only with trained installers of GSL

Compression Strength

3000 – 4500 psi


Corrugated steel deck.

Wear a NIOSH/OSHA approved dusk mask and/or provide ventilation when mixing the product.

This mix ratio should yield a slump of 8-10” when using a 2”x 4” section of PVC over a smooth plastic or glass sheet. Higher slumps will affect the final compressive strength, and for this reason the smallest slump possible to achieve the desired surface finish should be employed.

If after placement the product is not smooth and lump free, extended mix times with slightly more water (within the specified range) may be required. If separation or surface bleed occurs, reduce the water quantity to form a smooth, homogenous, flowable consistency. A working time of approximately 15 minutes should be anticipated, but will vary with temperature, humidity, and mixing consistency. Do not attempt to re-temper the mix once it begins to thicken. Using a guage rake and underlayment smoothing tool, work the material to the desired thickness and smooth the surface to remove as many remaining imperfections as possible.


For moisture sensitive floor coverings, test the underlayment prior to installation by the plastic sheet method per ASTM D-4263. If visible signs of moisture are present, then more curing time is required. Do not test GSL CSD for dryness using the calcium chloride method, ASTM F-1869, as inaccurate results will occur. After the underlayment has dried, remove any loose debris and foreign material. For tile and stone installations, a water proofing and crack isolation membrane is recommended but not required. For portland cement based adhesives, a floor sealer is recommended. Water-based adhesives will generally not require a floor sealer unless the porosity of the underlayment does not allow sufficient working time. Solvent based, or moisture cured urethanes do not normally require (and are normally not compatible with) a surface sealer. In applications where the floor goods manufacturer differs from these recommendations, the floor goods manufacturers’ recommendations will supersede all others. Consult an Dependable technical representative for additional details.


•  Minimum Steel Deck Standards: Minimum 22 guage galvanized steel deck with minimum flute depth of 9/16
•  Deflection Limits of the Structure: Live and dead loads considered, L/240    minimum. Dead loads only, L/360. Deflection limits of the decking material: L/480. More restrictive deflection limits may be required by some types of floor goods. Contact the floor covering manufacturer for minimum specifications.
•  Minimum Assembly Construction Criteria: Reference the Underwriters Laboratories Fire Resistance Directory for a full description of minimum criteria for each individual fire rated design.
•  When use with hydronic heating systems, GSL CSD must be poured to a thickness of 3⁄4” above the top of the tubing or 1” above the top of the flutes in the metal deck, whichever is greater.
•  Curing and Drying time before application of floor goods depends on thickness, humidity and ventilation conditions. At an average thickness of 1.25”, GSL CSD can typically be covered in 10-14 days. Thicker pours, humid conditions, and pour ventilation will require more extended drying times.
•  GSL CSD is NOT a wear surface.
•  GSL CSD is for interior use only and should not be used in areas where extended or repetitive exposure to moisture is anticipated unless protected by a waterproofing system.
•  GSL CSD is permeable to moisture vapor. In cases where moisture vapor drive is anticipated, such as over a crawl space or below grade, a moisture vapor barrier is recommended.
•  GSL CSD is approved for pedestrian foot traffic and light rubber wheeled traffic.
•  GSL CSD is not a structural cement and will crack where excess substrate deflection or dynamic loads that exceed the deflection limit of the substrate. Additional reinforcement is recommended where high dynamic loading is anticipated.
•  GSL CSD should not be used to bridge moving cracks or expansion joints. All joints must be honored through to the substrate.
•  Finished floor covering manufacturer recommendations supersede all others.