Mid-rise wood-framed buildings, traditionally rented as apartments, are now being sold as high-end condominiums. Residents of these buildings are losing patience due to the lack of code-mandated acoustic privacy, according to the PR Newswire.
In some cases, the condo owners of noisy buildings are suing developers, and a hard truth is coming to light: some long-accepted construction methods simply do not meet code.
Wood-Framed Buildings Can Be Loud
The acoustic performance referenced for building assemblies is often outdated.
“Many academic text and reference materials reflect acoustic performance data based on testing from 50 to 60 years ago,” says Alan Case, CIO of HushFrames. “For starters, today’s fast-growth framing lumber and the composition of current drywall panels test much differently.”
Building developers must take into account acoustic privacy when constructing or rehabilitating wood-framed structures.
“The days of turning a deaf ear to occupant complaints are ending,” says Case. “The smart strategy going forward is to educate the building designer with current testing data and insist on a comprehensive acoustic approach such as is done for thermal and moisture performance. After all, it’s what the code requires.”
Steel floor joists are non-combustible and resistant to extreme environmental and seismic loads making it one of the most resilient building materials available.
Cold-Formed Steel Floor Joists for Peace and Quiet
How can subfloors and floor joists be designed to better meet the acoustical demands of a building’s occupants? The answer is to use cold-formed steel (CFS) framing.
Use deep floor joists
A variety of CFS profiles, depths, widths, and thicknesses exist in the marketplace. The factor most relevant to sound attenuation is web depth.
“The deeper the joists, generally the better the sound insulation,” says Christoph Hoeller, research officer at the National Research Council of Canada (NRC). “Joist thickness bears little on noise impedance, so you should focus primarily on the joists’ depth and spacing.”
Place screws away from the web
In terms of fasteners, the subfloor should be screwed into the joist flange as far from the web as possible. Fastening the subfloor away from the stiff part of the joist allows the flange to act as a decoupling element, which can help attenuate some noise.
Other Sound Attenuation Factors
Other factors beyond the purview of the CFS flooring assembly are worth noting:
- Finish flooring. Heavy finish flooring adds mass. But a lighter material, such as carpeting, can soften the impact of footsteps and reduce the mechanical power injected into a floor.
- Sound mats. Resilient floor interlayers reduce impact noise. They can also reduce some airborne sound.
Recommended Resources
- Infographic: 5 Reasons to Use Cold-Formed Steel Floor Joists
- How to Engineer Subfloors and Cold-Formed Steel Floor Joists for a Little Peace and Quiet
- Cold-Formed Steel Design for Acoustic Code Compliance
- When Sound is “Green”