DamtecĀ® Acoustic Floor Underlay

Acoustic Floor
Two masses separated by a low frequency response isolator create the environment for noise and impact reduction many times greater than a single mass of equal weight. The isolator seeks to emulate the stiffness properties of the air, but as this space increases the frequency of the isolator governs the frequency of the floor system. If noise reduction is the primary goal then enveloping walls usually rest on the isolated floor. Ceilings with their own isolators cap the construction. If the frequency range is above 20 hz, neoprene is generally the best choice. If vibration or impact reduction is required, springs supporting the isolated floor by itself will normally suffice. The professional acoustician is the best person to make these evaluations. Thirty years ago several manufacturers working with Riverbank Acoustical Laboratories tested an isolated room under ideal conditions. Much of what was learned for attenuating high frequency noise (above 20 hz) and is been practiced by ABSOL.
The Riverbank tests showed that:
  • Only an acoustically separated "room within a room" construction could attain STC's
    (Sound Transmission Class) at or near 80.
  • Air Gaps heavily influence the performance of isolated floors and 1" should only be considered
    for impact.
  • Isolation of impact noise does not require "room within a room" construction, only isolated floors.


Natural Frequency establishes the response from one slab to the other. For the control of high frequency noise, 10 hz is the established criteria including dynamic stiffness correction. The elastomer must remain elastic, therefore the compounds and production procedures are critical as is ongoing verification of quality control. Long test histories have shown that 2" of air space should not be diminished. Neoprene floor isolators all perform below 8.5 hz. (report ESI, 10/15/97). Compounding is to AASHO specifications for highway materials, and molding occurs in the United Arab Emirates under the supervision of the ABSOL International LLc which operates under the quality guidelines set forth in Quality Standard MIL- I - 45208. The NF mounts combines the versatility and assurance of positive adjustable air gaps with the proven isolation of properly formulated neoprene. It eliminates the possibilities of rot, vermin, and biologically unsafe conditions that could occur in older form work type systems. This brochure highlights installations, specifications and typical details. Your application may be different. Any thoughts or specific questions you have we would be most pleased to address.


Floor System Construction Procedure:
1.    The setting of all isolation materials shall be performed by or under the supervision of the isolation manufacturer. 2.    Set and waterproof any drains and lower pipe seals in keeping with waterproofing specifications. 3.    Cement perimeter isolation board around all walls, columns, curbs, etc. 4.    In seismic zones intersperse the perimeter isolation board with bridge bearing quality neoprene pads the thickness of the isolation board. 5.    Place individual neoprene isolators on the sub-floor at a maximum spacing of 48"(1200mm) in strict accordance with the approved drawings prepared by the isolation manufacturer. 
Additional reinforcement 6.    Must be detailed on isolation manufacturer's drawings when required. If sound barrier isolation walls are used, add the following: Perimeter isolators shall be selected to support the wall weight in 7.    Addition to the perimeter of the floating floor. 8.    In seismic zones provide anchorage for the double acting resilient vertical snubbers to the structural slab. Snubber anchor bolts must be in close proximity to the mechanical snubbers restraining any high center of gravity equipment to withstand the overturning moments generated by the machinery snubbers and prevent failure of the floating floor. 9.    Cover isolators with 1/2 "(12mm) AC plywood. Isolators shall be located under joints and joints staggered. Connect plywood at abutting edges and corners with 16 gauge steel junction plates. 10.  Cover the plywood with 6 mil (0.15mm) plastic sheeting and carry it up the walls past the perimeter isolation. 11.  Place seismic snubber housings on the anchor bolts that protrude from the structural floor and through the plywood. 12.  Place reinforcing as shown on the drawings and pour floor monolithically. 13.  After the concrete has hardened, caulk all perimeter isolation board. 14.  In seismic zones adjust the double acting snubbers after machinery is in place to provide a maximum up and down clearance of 0.125"(3mm).
Quality Assurance
Floating floor system components shall be designed and fabricated by a manufacturer with at least five years experience in fifty similar installations. The floating floor isolation materials and panel board forms shall be installed under the supervision of the isolator manufacturer.

Site Conditions
If site conditions are unsatisfactory or raise questions about the installation of the floating floor, the work will not proceed until the condition has been corrected in a manner acceptable to the isolation manufacturer.

Sequencing and Scheduling
Coordinate work with other trades and coordinate scheduling with the construction supervisor to minimize delays.

Type AC exterior grade 1 (12mm) thick.

Install the floating floor systems according to the installation and adjustment procedures and drawings submitted by the isolator manufacturer and approved by the architect.

Neoprene supported floating floor system is to be constructed utilizing cast in place isolation mountings. Housings are to be designed to sequentially lift the floating slab to desired finished elevation after concrete has cured. Neoprene isolation element is to be molded to AASHO standards in accordance with table 1 as shown below. Deflections shall be between .20" to .30". Isolator natural frequency shall not exceed 10 hz including dynamic stiffness correction. Verification of natural frequency shall be at a nationally recognized test facility that is ISO 9000 certified. Casting heights including extensions shall accommodate a floor thickness of " 150 "and accommodate an air space of " 2". Castings will have provisions for chairing woven wire mesh reinforcing or two 1/2" diameter reinforcing bars. Actual rebar size and spacing shall be as determined by the project's structural engineer. An accessory neoprene locator plug will seal the threaded portion of the housing from concrete during the pour. The floating floor shall be kept clear of the perimeter walls or rectangular penetrations utilizing perimeter isolation board manufactured from either 3/4" thick 10 lb. coated fiberglass or 1/2" thick neoprene sponge rubber. All cylindrical penetrations shall use neoprene cylindrical covers. Six mil plastic sheeting with seams overlapped a minimum of 24" turned up and over all perimeter isolation shall act as a bond breaker during pour. Type FFD floor drains shall be used where slab drainage is required. A non-hardening pour grade caulking shall be used to seal the perimeter board and floor after final height adjustments if waterproofing is required. Submittals shall include casting details and neoprene load versus deflection information. ISO 9000 natural frequency test data as outlined above shall be part of this submittal. Manufacturers shall have a minimum of 5 years experience in this field. All components shall be manufactured in the U.A.E., not just assembled. Products shall be type NF as manufactured by ABSOL International LLC.
Data Sheet

Designed and Hosted By Infobahn Consultancy