Huber Engineered Woods EXACOR MgO Underlayment 1/2″ 4' x 8'

EXACOR MgO underlayment is a 1/2-inch magnesium oxide cementitious panel with proprietary layered glass-fiber mesh reinforcement that transforms multifamily and light commercial construction schedules. At 86.4 pounds per 4’x8’ panel (2.7 lbs/sq ft), it’s light enough for framing crews to handle yet delivers integrated fire and sound performance without wet-poured gypsum’s week-long cure times.

The game-changer? Zero cure time. Contractors report gaining 3-4 weeks in their schedules compared to traditional gypsum underlayment. Jose Romero from F&G Carpentry noted that framing crews can learn installation in 5 minutes — meaning the same crew that installs your subfloor can keep working straight through to underlayment without bringing in specialized trades.

Time and Labor Advantages That Actually Matter

The 30% faster installation compared to wet-poured alternatives isn’t just manufacturer hype. Matt Limpert from Ridgehouse Construction stated the product ‘exceeded expectations’, while Todd Hardy from TDK Construction emphasized the time-is-money aspect and schedule addition. No pump trucks. No sand mixing. No water mess on site. No waiting 5-7 days for moisture to evaporate before you can continue work.

Montana’s short construction season makes these schedule gains critical. When you’re racing to close in before October freeze-up, eliminating a week of cure time can mean the difference between finishing on schedule and scrambling through winter conditions. The panels install dry over AdvanTech subflooring or standard OSB using approved corrosion-resistant fasteners.

Fire and Sound Performance Without Compromise

EXACOR delivers 1-hour fire-resistance ratings in specific UL assemblies while contributing to STC and IIC ratings without requiring a separate sound mat. That’s two code requirements handled by one panel. Jim Waters from De Moda Floors highlighted sound rating as a key factor for projects — critical for multifamily where tenant satisfaction depends on acoustic separation.

The panel meets fire performance through UL assemblies L528, L501, L502, L525, L602, and M500, with ICC-ES reports ESR-4634 and ESR-4635 backing up the claims. Unlike layered assemblies that depend on perfect installation of multiple components, EXACOR’s inherently non-combustible magnesium oxide core delivers consistent performance.

Specification	Value
Thickness	1/2 inch (nominal 12mm)
Weight	2.7 lbs/sq ft
Fire Rating	1-hour in specific UL assemblies
Acoustic Performance	Contributes to STC/IIC without separate mat
Available Sizes	4’ x 8’, 4’ x 9’, 4’ x 10’
Edge Profile	Straight (Square)

Montana’s temperature extremes — from -40°F arctic outbreaks to 100°F summer heat — destroy lesser materials. EXACOR’s magnesium oxide core with glass-fiber mesh reinforcement does not warp, expand, cup, or delaminate when exposed to moisture. No callbacks for squeaky floors. No warranty claims for buckled underlayment. The dimensional stability matters when your reputation rides on every installation.

The Bottom Line for Montana Contractors

EXACOR makes sense for multifamily residential, light-commercial buildings, student housing and senior living facilities where schedule compression and integrated performance justify the material investment. The Enhanced Experience warranty program requires project registration and a pre-construction meeting — typical commercial project requirements that won’t faze professional contractors.

Worth considering? Absolutely, if you’re building multifamily or light commercial projects where fire and sound ratings are mandatory. The schedule gains alone can offset material costs on projects where winter weather threatens completion. Not every job needs MgO underlayment — single-family homes without fire separation requirements won’t see the same value. But for the right application, EXACOR delivers measurable advantages over traditional wet-poured systems.

The product ships 38 panels per unit and works with standard finish flooring materials including tile, carpet, hardwood, and LVP/LVT. Installation follows manufacturer documentation including their Installation Manual (HUB-82366) and Product Installation Checklist.

FAQ

Can existing framing crews really install EXACOR without specialized training? Yes — F&G Carpentry reported their framing crews learned installation in 5 minutes. The dry-fit panels install directly over wood subfloor using approved corrosion-resistant fasteners. Crews familiar with sheathing installation already have the skills needed.

What flooring materials can go over EXACOR underlayment? EXACOR accepts tile, carpet, hardwood, and LVP/LVT finish flooring materials. The stable substrate works with any standard flooring system.

Does EXACOR require special joint treatment? Panels should be staggered with joints following the manufacturer’s layout checklist. Joint treatment requirements vary by assembly type — some fire-rated assemblies require specific joint treatment while others don’t.

How much time do contractors actually save versus gypsum underlayment? Ryan Carrier (Owner/Construction Manager) reported gaining 3-4 weeks in schedule. The time savings come from eliminating the 5-7 day cure time plus faster installation — approximately 30% faster than wet-poured systems.