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Acoustik Underlayment used for Bonus Room Flooring


Bonus rooms above existing living spaces are often great places to not only add square footage to a residence but be used as a “get away” for the home owners.  These rooms which were used as attics often times provide spaces where home owners can relax and enjoy.  The fact that these areas are above the rest of the house introduces a clear need for some acoustical floor treatment for some of the rooms.

Mr. Dreher contacted me about an installation that he was considering that had a unique quality.  Although the idea of converting the attic into a usable, livable space was not necessarily a new idea, his consideration for a finish floor was.  The idea was to get some extremely expensive, extremely rare re-claimed lumber that has spent years and years submerged under water.  This extremely beautiful wood was critical to the aesthetic that he envisioned for the room.  The 3rrd floor loft was directly above the bedrooms and an office on the second floor, so clearly keeping the footfall and airborne noises out of those areas was critical.

In order to make this room useable, some significant structural changes needed to be made to cover the HVAC services and the like.  As one of the picture shows, a secondary truss/flooring grid was constructed which allowed for a level floor in the room.  On top of this framing system a standard tongue-and-groove sub floor was installed.  A couple saw fits and some additional framing and things were ready for the underlayment.

The Acoustik underlayment is adhered to the sub floor with a two-part adhesive called DA-5.  This 5 gallon pail is applied with a 3/16” notched trowel and the Acoustik underlayment is then put on top of the grooves of adhesive.  After the floor is covered with the rubber underlayment, a topical adhesive called Poly 300 is used to hold the finish floor to the top of the rubber.  It is critical to the acoustical integrity of the flooring system that no fasteners penetrate the rubber membrane.  If this happens, a significant amount of vibration is allowed to flank the underlayment via hard surface to hard surface contact and the finish floor is no longer “floating.”  Due to our extensive amount of testing, and as long as we are given full disclosure of the construction materials and proposed installation methods, we are able to carry the warranty of the finish floor.

The advantage of the 3/8” Acoustik underlayment over other similar products is significant.  The largest of these advantages is the dual-durometer of the rubber used.  Because two different “relative hardness” rubbers are used, the product is extremely effective at absorbing the energy of impact and improving the IIC of the floor/ceiling assembly.  The rubber used is extracted from used car tires (after pulling out the steel and nylon) which is a much better use for the rubber than the tire sitting in a landfill somewhere.  Considering the fact that it is rubber, this product should last a long, long time.  

Although, in this case, Mr. Dreher did not have any experience with the flooring assembly before the Acoustik and re-claimed wood were installed, he did report the following: 

“…The product appears to have accomplished our goal of minimizing noise and vibration from our 3rd Floor Loft into the 2nd Floor Bedrooms and Office below.  Since we don’t have anything to compare it against, due to the fact the previously the 3rd Floor was unfinished attic space, it’s difficult to gauge any before and after measurement.

However, I do know that we made the right choice in using the Acoustik underlayment and I continue to promote the product/solution to everyone that visits the space, especially if they’re in the design and construction fields.

Let me know what else to touch upon or highlight, as well as any particular technical verbiage that would be best for you folks…and I’ll be glad to oblige.

All the Best,



P.S.  Not yet started rebuilding task of the main stair that accesses the 3rd Floor Loft.  Usability of the space will go up dramatically once we complete that final activity….stay tuned for final photos.

If you have any questions about this or a similar installation that you are considering, please feel free to contact Ted Weidman (800-527-6253 ext. 25) or [email protected]