Cementitious Underlayment in the Twin Cities
When the spec calls for a substrate that can handle forklift traffic, wet-area exposure, or a 48-hour return to service that gypsum cannot deliver, cementitious underlayment is the answer. ATR Floors installs self-leveling, high-strength cement-based underlayment systems — including Combimix CM 920/960 series polishable toppings and CM 960 Industrial Super Top — across the Twin Cities metro.
7,000+ psi
Industrial Super Top Strength
2–4 hrs
Walkable Rapid-Set
Combimix
CM 920 / 960 Certified
Where Cementitious Underlayment Beats Gypsum
Both gypsum and cementitious underlayment are pumpable, self-leveling substrate systems — but they serve different conditions. Cementitious wins when strength, moisture, or schedule push past gypsum's envelope.
Wet-Area Exposure
Cementitious is cement-based and will not deteriorate in wet areas. Bathrooms, commercial kitchens, lobbies with exterior door exposure, pool decks, and mechanical rooms all call for cementitious over gypsum.
Higher Compressive Strength
Standard systems deliver 3,000–5,000 psi; industrial-grade toppings like Combimix CM 960 Industrial Super Top exceed 7,000 psi. Gypsum tops out at 2,500–3,500 psi.
Rapid Return to Service
Rapid-set cementitious systems are walkable in 2 to 4 hours and ready to receive floor covering in 4 to 24 hours. Standard gypsum requires 14 to 28 days of cure before floor covering installation.
Polishable Toppings
Combimix CM 920/960 toppings can be polished, stained, or sealed as the final floor surface — no floor covering required. Integral color and aggregate options for decorative applications.
Industrial & High-Traffic
Retail, warehouse, distribution, and manufacturing applications where rolling loads, pallet jacks, and chemical exposure exceed the capabilities of gypsum.
Substrate Versatility
Bonds to existing concrete, plywood/OSB (with lath), metal deck, lightweight concrete, and even properly prepared tile or terrazzo in renovation projects.
Combimix Product Lines
ATR Floors installs the full Combimix commercial underlayment and topping line. Product selection depends on compressive strength, decorative requirements, and finished floor type.
Why Choose ATR for Cementitious Underlayment
High-Strength Toppings
Combimix CM 960 Industrial Super Top exceeds 7,000 psi — forklift, pallet jack, and chemical exposure rated.
Clean Slate Substrate Prep
Chemical removal of coatings and contaminants — no grinding, no silica dust before the pour.
2-Year Workmanship Warranty
Written warranty on pour quality, flatness, and adhesion. Material warranty separately from Combimix.
Rapid Schedule Compatibility
Walkable in hours, ready for floor covering in 4 to 24 hours on rapid-set systems.
Industries We Serve With Cementitious
Frequently Asked Questions
Cementitious is cement-based: higher strength, moisture-tolerant, and faster curing. Gypsum is gypsum-based: lighter weight, integral to fire-rated UL assemblies, and the primary contributor to STC/IIC sound control in multifamily construction. The choice depends on code, moisture exposure, and structural loading. Many projects use both — gypsum in residential floors, cementitious in lobbies and wet areas.
Rapid-set systems are walkable in 2 to 4 hours and ready for floor covering in 4 to 24 hours. Standard-set systems require 24 to 72 hours. Polishable toppings (Combimix CM 920/960) typically cure for 7 to 14 days before grinding and polishing begins.
Yes. Combimix CM 920 and CM 960 series toppings are specifically formulated for diamond polishing. They can be ground, honed, and polished to the same gloss levels as site-cast concrete — from a matte hone to a high-gloss mirror finish. Integral color and aggregate options are available.
Standard self-leveling systems: 3,000 to 5,000 psi. High-performance toppings (Combimix CM 960): 5,000 to 7,000+ psi. For comparison, standard gypsum underlayment achieves 2,500 to 3,500 psi, and typical cast-in-place concrete achieves 3,000 to 4,000 psi.
Yes. Unlike gypsum, cementitious is cement-based and will not degrade when exposed to moisture. It is the standard substrate choice for commercial kitchens, bathrooms, locker rooms, pool decks, and any area where standing water or high humidity is expected.
The Substrate Determines the Floor. Get the Substrate Right.
Include sq ft, substrate type, intended floor covering, and project schedule. We respond within one business day.