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When considering subflooring and underlayment assemblies for multifamily builds, gypsum underlayment has been the go-to for more than 30 years. But a newer solution has entered the market with impressive outcomes.

EXACOR™ magnesium oxide (MgO) panels challenge the incumbent with a heavy-hitting promise -- fast, accurate installation with sound attenuation and fire-resistance benefits.1 All without the additional trade and cure times needed for gypsum concrete underlayments.

How does EXACOR perform toe-to-toe against gypsum underlayment? TDK Construction, based in Murfreesboro, Tennessee, has a few notes. The development and construction company installed EXACOR in a luxury apartment complex project, documented in a recent case study.

Here are the top 5 reasons their build teams wish their architects would abandon gypsum underlayment:

  1. Easy installation with one less trade on the build site.
  2. Accuracy from floor to floor means fewer surprises.
  3. Smooth, dimensionally stable panels keep up the momentum.
  4. Acoustic performance with fire-resistant protection.1
  5. Less mess, less stress with the strength of magnesium oxide.


Easy installation with one less trade on the build site

EXACOR’s subflooring and underlayment solutions offer fast installation by reducing the number of trades on site. Unlike gypsum underlayment assemblies that require hiring additional subcontractors and waiting on cure times, existing framing crews can install EXACOR underlayment panels over plywood or OSB subfloors, so construction can continue without delay.

“It was faster than laying just traditional subfloor,” said Todd Hardy, supervisor for TDK Construction. “Time is money and if we can save time on one job, let alone all our jobs, that really adds up.”

Hardy estimated a $30,000 cost savings on their budget and nearly two months shaved off their build timeline.2 TDK’s framing crew worked quickly and were already on site to install the EXACOR underlayment over the subfloor they had just completed. They didn’t need to hire additional subcontractors or wait for cure times like with gypsum concrete underlayment.


Accuracy from floor to floor means fewer surprises

EXACOR magnesium oxide panels..

Another benefit? For TDK, eliminating gypsum underlayment meant they didn’t have to make any adjustments to door headers on the second or third floors, since there weren’t variances in the thickness of EXACOR underlayment. With gypsum underlayment, this precision isn’t always guaranteed, causing headaches for crews down the road.

“Our framers could prefab everything, they don’t have to worry about the first, second, third floor being different,” Hardy said. “With gypsum, there were always unknowns, things you wouldn’t discover until you’re deep into the construction process.”


Smooth, dimensionally stable panels keep up the momentum

Anticipating weather-related delays is part of the uncertainty of any build project. But atmospheric conditions like humidity can also impact cure times of wet-laid gypsum underlayment. Crews can’t make progress until they have a solid surface, which can spell disaster for tight schedules.

EXACOR magnesium oxide panels..

EXACOR streamlines a solution to this issue with smooth, dimensionally stable panels that don’t require cure times. And it eliminates the need to coordinate another trade on the site, since existing framing crews can easily install it as both a subfloor underlayment over traditional OSB or plywood (UL 263 L528) and as a structural subfloor (UL263 L601).

“At TDK Construction, everything we build, we own. Our owner and developer are all about getting it done, and they were super happy with the results,” Hardy said about EXACOR.


Acoustic performance with fire-resistant protection

EXACOR underlayment panels can help meet the fire rating, sound rating and dimensional stability requirements of most multifamily and light commercial job sites when used as part of certain tested assemblies.1 EXACOR panels are also fire resistant3 due to a magnesium oxide formula and provide strength and stability due to the integrated mesh core for structure.

EXACOR magnesium oxide panels..

“The fire marshal’s main concern is always meeting the UL rating — it needs to maintain a one-hour [fire-rated] floor assembly,” Hardy said. “When we put the subfloor in and then the EXACOR underlayment, the UL rating was achieved.”4

As for sound? EXACOR offers sound attenuation benefits to help address both airborne noises like talking, music or appliances, and impact noises like footfall, dropped items and furniture movement.

“With construction projects like ours — a three-story building — you want to make sure you alleviate all the sound from above, and that is always one of the architect’s biggest challenges,” Hardy said. “With the gypsum underlayment assembly we’ve used in the past, we had to add a sound mat between the gypsum and the finished flooring. This was eliminated with the EXACOR underlayment assembly.”4


Less mess, less stress with the strength of magnesium oxide

An added bonus for crews? Less mess. EXACOR can eliminate cleaning headaches associated with gypsum underlayment, such as spills, difficulty around tub framing, threshold unevenness, and more.

“Not to mention the mess that the wet-laid gypsum crew can make — it gets everywhere. On the walls, on the tubs, all over the place. And we spend a lot of time just cleaning it up,” Hardy said.


TDK’s main takeaway

With so many boxes checked, EXACOR impressed TDK with its ease of installation and savings on time and costs.

“Our construction supply company sales rep had other contractors in the area say they were skeptical, but as we were laying EXACOR underlayment down, they saw how quick [the process] was,” Hardy said.

Builder-approved solutions can go a long way for efficiency in multifamily design-builds. For TDK’s 127-unit luxury apartment complex, EXACOR proved it delivers on its promises.

“We’ll use this for everything going forward,” Hardy said.

Read the full EXACOR + TDK case study.



  1. EXACOR panels may be used in specific published sound and fire-resistance-rated floor/ceiling assemblies. Follow published fire-resistance rated assembly requirements and consult local building codes and designer of record for fire-resistant design requirements.
  2. Pricing and time savings will vary by project and/or region. Check with your local channel partner on pricing and availability.
  3. ASTM E119 - Standard Test Methods for Fire Tests of Building Construction and Materials. EXACOR subflooring panels may be used in specific published fire-resistant-rated floor/ceiling assemblies. Follow published fire-resistance rated assembly requirements and consult local building codes and designer of record for fire-resistant design requirements.
  4. This job was designed in accordance with UL L528. Click here to see the assembly specifications (PDF). Sound and fire ratings vary by assembly. Refer to the EXACOR Sound & Fire Assemblies Handbook (PDF) available at