Corporate Office - Thorburn Associates
Corporate Office - Thorburn Associates
Corporate Office - Thorburn Associates
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THORBURN ASSOCIATES INC.<br />
Acoustic and Technology Consultants<br />
Newsletter<br />
Summer 1997<br />
Thank you to everyone who has responded to our request for e-mail addresses! For those of you who<br />
are “wired” but still receive our newsletter in the mail, send your electronic address to TA@TA-Inc.com.<br />
We’ll lighten your snail mail pile by sending future newsletters to your computer. Don’t worry, we won’t<br />
attach graphics to the file. Everyone knows it’s no fun sitting around waiting for a huge file to open! The<br />
graphics will be located on our website if you’re interested in having the picture that goes with the story.<br />
Fiberboard Facts<br />
By whatever name you call it: Fiberboard, Beaver board, sound-deadening board, Celotex TM , or<br />
Homasote TM , this material seems to be making a comeback with potential acoustical uses. But before<br />
you decide to add it to your next project, you should know that this compressed fiberboard does not add<br />
any positive acoustical effects in most constructions. We have found that, with a couple of exceptions,<br />
replacing the fiberboard with a gypsum board product or plywood usually results in a higher-rated<br />
acoustical construction.<br />
Testing the Walls<br />
Let's start out by examining wall assemblies. The original sound tests using fiberboard were done under<br />
a now-obsolete 1967 standard. In this test, the fiberboard and gypsum board were glued to the framing<br />
studs. An analysis of the test results shows that the fiberboard provided some (but not all) of the<br />
benefits resilient channels are known for.<br />
This installation method is the main weakness with that acoustic test. Most building inspectors in<br />
California will not allow you to glue fiberboard to the wall and then glue gypsum board over it. In fact,<br />
when was the last time you built a wall by simply gluing it together? Some type of mechanical<br />
connection is required to bond the layers, even when resilient channels are used. This is also important<br />
to consider from a longevity point of view. But as with resilient channels, mechanical connections need<br />
to be carefully installed to avoid compromising the acoustic benefits of the assembly (a topic covered in<br />
our Spring 1996 newsletter).<br />
When attaching the gypsum board to the resilient channel, any screws which accidentally connect with<br />
the framing members will short-circuit the assembly by locking the resilient channel in place. Once this<br />
happens, all flexibility is lost and the channel is worthless. Likewise, if we screw the gypsum board into<br />
the framing member behind the fiberboard layer, then the resiliency found in that original glue-up test<br />
will be lost. On the other hand, if you actually plan on driving fasteners through the board layers and<br />
into the framing, you would be much better off simply replacing the supporting fiberboard with another<br />
layer of gypsum product.<br />
<strong>Corporate</strong> <strong>Office</strong><br />
Regional <strong>Office</strong><br />
Regional <strong>Office</strong><br />
Castro Valley, California<br />
Burbank, California<br />
Morrisville, North Carolina<br />
Page 1<br />
Tel: 510-886-7826<br />
Tel: 818-569-0234<br />
Tel: 919-463-9995
Resilient Channel Assembly (with batt insulation) - STC 52<br />
Fiberboard Underfoot<br />
Fiberboard Assembly - STC 46 to 50<br />
A thicker version of a fiberboard panel is sometimes used for a subflooring system in wood frame<br />
constructions. While its fibrous composition might help reduce some footfall noise heard between<br />
stacked units, it is too lightweight to act as a barrier material in the same manner that a plywood subfloor<br />
Page 2<br />
<strong>Corporate</strong> <strong>Office</strong><br />
Regional <strong>Office</strong><br />
Regional <strong>Office</strong><br />
Castro Valley, California<br />
Burbank, California<br />
Morrisville, North Carolina<br />
Tel: 510-886-7826<br />
Tel: 818-569-0234<br />
Tel: 919-463-9995
with lightweight concrete or gypcrete would. In these cases, the advantage of using fiberboard is offset<br />
by the limited number of facilities where it will make a difference.<br />
Using fiberboard as a carpet underlayment also provides mixed results. We have found that applying<br />
fiberboard on top of a floor system provides no additional sound isolation from unit to unit. If the carpet<br />
is thick and well-padded, the footfall noise or impact isolation of a floor/ceiling assembly is not<br />
significantly affected. However, as an underlayment for thin or lightweight carpets without pads, the<br />
Homasote TM product would help reduce impact noise into the room below.<br />
The Care and Feeding of Fiberboard<br />
One important precaution to observe with fiberboard is keeping the material dry during construction. We<br />
were called upon to provide expert testimony for a project where a contractor had substituted (without<br />
the architect's permission) fiberboard for a floor design system of plywood and gypcrete. During a<br />
rainstorm the floor system was allowed to get wet, causing the fiberboard to expand and buckle.<br />
In the long run, the pending lawsuit claimed acoustical, structural, and numerous additional damages<br />
because the owner was not happy with the finished product. Needless to say, had the original design<br />
detail of a plywood subfloor with a gypcrete system been utilized, much of the unevenness caused by<br />
water damage could have been avoided. Also, certain acoustical problems in the facility might have been<br />
avoided as well.<br />
Don't get us wrong; as part of a construction crew during high school and college many of the first<br />
buildings we worked on in Michigan used fiberboard as an infill underneath the exterior sheeting. In this<br />
geographical location shear plywood is not required along the entire exterior wall -- only at the corner.<br />
While fiberboard can be useful for replacing plywood or gypsum board in some assemblies, we feel that<br />
its true acoustical values are extremely limited. This is basically because it is too rigid to act as a resilient<br />
connector, and not absorptive enough to substitute for an absorber such as batt insulation.<br />
TA Principal Wins ICIA Award<br />
We’re proud to announce that Steven J. <strong>Thorburn</strong> received the ’96-’97 ICIA Professional Education and<br />
Training Committee (PETC) award at the 10 th annual ICIA Achievement Awards Presentation.<br />
This year’s ICIA (International Communications Industries Association) awards ceremony was held during<br />
the recent InfoComm International trade show in Los Angeles. A note for anyone who attended that<br />
show: the Ultimate Digital Theatre, located upstairs in th econvention center, showcased not only the<br />
newest digital technologies, but some examples of Steve’s acoustical work as well.<br />
Walt Blackwell, ICIA’s Executive Director, told the crowd, “Steve has been instrumental in many ICIA<br />
training venues over the years. He and his company have also provided all of the audio and video<br />
system engineering for the ICIA Academy in Fairfax, Virginia.”<br />
Founded 58 years ago, the ICIA is an organization which has supported the audiovisual industry from the<br />
early days of film and slide to today’s computer and video industry. Their PETC award is given to<br />
recognize a person whose continued participation in education and training within the communications<br />
industries promotes the newest technologies and methods, provides methods to successfully compete in<br />
the global market, fosters professionalism within the trade, and promotes the industry as an exciting<br />
career opportunity.<br />
<strong>Corporate</strong> <strong>Office</strong><br />
Regional <strong>Office</strong><br />
Regional <strong>Office</strong><br />
Castro Valley, California<br />
Burbank, California<br />
Morrisville, North Carolina<br />
Page 3<br />
Tel: 510-886-7826<br />
Tel: 818-569-0234<br />
Tel: 919-463-9995
Going to ISTC or IAAPA?<br />
Meet some of the TA staff and learn about our recently completed large format theatre and themed<br />
entertainment projects during our annual trade show route at:<br />
• International Space Theatre Consortium<br />
Booth # 29, September 19 – 22 in Vancouver, Canada<br />
• International Association of Amusement Parks and Attractions<br />
Booth #531, November 17 – 22 in Orlando, Florida<br />
Copyright 1997<br />
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THORBURN ASSOCIATES INC.<br />
Acoustic and Technology Consultants<br />
<strong>Corporate</strong> <strong>Office</strong>: Castro Valley, California Tel: 510-886-7826<br />
Regional <strong>Office</strong>: Burbank, California Tel: 818-569-0234<br />
Regional <strong>Office</strong>: Morrisville, North Carolina Tel: 919-463-9995<br />
TA@TA-Inc.com<br />
www.TA-Inc.com<br />
eNews@TA-Inc.com<br />
General Information Email Address<br />
Web Site<br />
Newsletter Issue<br />
<strong>Corporate</strong> <strong>Office</strong><br />
Regional <strong>Office</strong><br />
Regional <strong>Office</strong><br />
Castro Valley, California<br />
Burbank, California<br />
Morrisville, North Carolina<br />
Page 4<br />
Tel: 510-886-7826<br />
Tel: 818-569-0234<br />
Tel: 919-463-9995
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