Fire Rating, Sound Rating, Flat Floor
If you build wood-frame multifamily, hotels, or senior living, gypsum concrete underlayment is doing three jobs in your floor/ceiling assembly at once:
Fire. Poured gypsum concrete is an integral component of UL-rated floor/ceiling assemblies. The Treadstone® line we pour is UL Listed in over 100 designs (per Formulated Materials), and the material has zero flame spread per ASTM E84.
Sound. Gypsum concrete adds the mass that blocks airborne sound (STC), and over an acoustic mat it decouples footfall impact (IIC). This mass-plus-mat topping is, in practice, how wood-frame multifamily meets its required sound ratings. Full teaching on STC vs IIC lives on our Sound Control Systems page.
Flatness. Poured at 3/4″ to 3″ thick, gypsum concrete self-levels over wood-frame deflection, plumbing grooves, and panel seams, handing your flooring installers a flat, monolithic substrate.
The numbers architects spec: compressive strengths of 2,000 to 4,000+ PSI per ASTM C472, density around 110–120 lb/ft³, roughly a quarter lighter than standard concrete, which is why wood framing can carry it.
Specified on Paper, Proven at the Pump
The spec is only as good as the batching. A gypsum underlayment specified at 2,500 PSI can leave the pump at 1,600 PSI if the crew over-waters or over-sands the mix, and hand-batching by bag count and eyeballed water makes that drift routine. We took the guesswork out of the chemistry: the Smart Batch® GC-1 weighs every ingredient of every batch against your programmed mix design, one half-ton batch every 75 seconds, and archives every batch to a cloud server. The QC report goes in your closeout file.
Radiant Heat Encapsulation
Hydronic radiant tubing stapled to a subfloor needs full encapsulation in a thermal topping, typically 3/4″ to 1.5″ of gypsum-based material over the tube. Done right, the topping locks tubes in place, spreads heat evenly across the floor, and adds fire and sound mass in the same pour. Our computer-batched pours place the topping at consistent, specified water content, which matters twice over radiant tubing: consistent density for even heat transfer, and predictable dry times before the flooring goes over it.
Treadstone®: Proven Chemistry, Documented Placement
We install Treadstone® gypsum concrete underlayment by Formulated Materials: FR25 with compressive strengths up to 3,200 psi and FR30 up to 3,800 psi (ASTM C472), fast-setting formulations that take light trade traffic in 1 hour and normal traffic in 24 hours (per Formulated Materials). The line is engineered for fire-rated and sound-rated assemblies, radiant heat encapsulation, and high-strength applications, and it feeds our batch plant in bulk supersacks, because the Smart Batch® GC-1 and Treadstone® come from the same family of companies. As a Formulated Materials partner for the Pacific Northwest, we also install their acoustic mat systems where the spec calls for them.
Where we pour it:
- Wood-frame multifamily: apartments and townhomes
- Hotels and hospitality
- Senior living and student housing, where fire and sound ratings are both non-negotiable
- Radiant heat encapsulation
- Renovation and change-of-use projects chasing a new fire or sound rating
