BUILDING SUPPLY INDUSTRY ASSOCIATION - November/December 2018 - 13
BY CHRIS MASKELL, BUSINESS DEVELOPMENT MANAGER
IS AN UNDERLAY WITH
A 60+ IIC RATING GOING
TO SOLVE MY NOISY
o understand why an underlay with a
60+ IIC rating may not fix a noisy floor, we
must first explain the sound measurement
rating systems IIC and STC:
* IIC (Impact Isolation Class) measures noise generated
by impacts such as dropped objects and footsteps.
* STC (Sound Transmission Class) measures audible noise
such as voices and stereos.
It is important to note that ratings for both IIC and STC
are awarded based on certain test criteria, which usually
involves testing underlayment and floor/ceiling assemblies
together. When tested together, higher IIC and STC
scores are achieved - the higher the rating the better the
ASTM International provides standards for such testing.
You will usually see references to test their standards ASTM
E-492 or ASTM E-1007 (downloadable at www.astm.org) in
the literature that comes with the acoustical underlayment.
These standards explain the test conditions under which the
underlay achieved its IIC and STC ratings.
With this understood, addressing acoustical issues in
existing buildings by adding high density foam or mat
underlayment's is not a sure way to fix noise issues. In
fact, expectations are usually not met.
Yes, you can easily buy an acoustical underlayment that
claims a high (60+) IIC/STC rating, but can you be sure it
will perform to this level in your home/condo? How much
will noise be reduced? It is important to understand that
an acoustic rating can only be associated with a substrate
assembly, not a single product.
Therefore, before you make your purchase, ask two
1. Under what test conditions (ASTM) was the acoustical
underlay you're considering tested when it achieved its'
2. Do these test conditions (including floor ceiling
assembly) match my situation at home?
The bottom line: for an underlayment to provide its
acoustical rating in your home, your subfloor and ceiling
assembly must be the same as those present when the
underlay was tested.
For example, a 1/8-inch (3mm) high-density foam
underlay tested over an 8-inch slab will obtain a higher
IIC and STC rating than the same underlay tested over a
6-foot concrete slab. So, how thick is your concrete slab?
Add a drop ceiling and you further increase the acoustical
barrier and the IIC and STC ratings. If you have wood frame
construction, with no acoustical topping, and hope an
underlay with a high IIC and STC rating is what you need to
make your neighbor below happy, you are mistaken.
Know that each building is a little different and,
depending on the situation, some assemblies using
hard-surface flooring in combination with the right
membrane can provide a comfortable environment.
No acoustical barrier on the market place can arbitrarily
claim to provide a level of sound absorbency in all
scenarios. In fact, they don't. What they are claiming
though is that under very specific test situations the
underlay product and substrate together achieved the
advertised IIC/STC ratings. With the right combination of
assembly and underlay, comfort can be provided.
In short, there are no easy solutions to reduce noise
transfer in existing buildings. Faced with this reality many
home owners resort to placing area rugs through living areas
and adjust their lifestyle to become quieter neighbours.
NOVEMBER/DECEMBER 2018 | BCFCA NEWS | NEWS MAGAZINE
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