By Julie Fischer, INCE, LEED AP BD+C
When designing spaces that prioritize acoustic comfort, whether hospitals, schools, or office buildings, sound isolation is often a top concern. Although, one critical factor frequently overlooked is the stud gauge used in wall partitions. It’s not just a structural detail; it’s an acoustic performance driver.
The gauge of a stud is strongly tied to the overall sound isolation performance of a partition. Why? Because the stiffer the stud, the more sound can transmit through the wall assembly. In other words, a heavier gauge may seem like a win for structural support, but acoustically, it can work against you.
Most industry-standard STC (Sound Transmission Class) ratings are based on 25-gauge studs. These ratings inform specifications, compliance, and even certifications such as LEED, Facilities Guidelines Institute (FGI), or Collaboration for High Performance Schools (CHPS). However, in recent years, the industry has shifted toward using 20-gauge and 20-gauge equivalent studs more prevalently. This change, often driven by structural or cost considerations, can unintentionally lead to partitions underperforming in real-world conditions.
Consider a standard partition: two layers of drywall, full height, with batt insulation.
- With 25-gauge studs, this assembly typically achieves an STC of 45.
- Swap those for 20-gauge studs, and the STC drops to approximately 40.
- Go heavier—18 or 16 gauge studs—and performance declines even further.
That’s a significant difference, especially in environments where acoustic privacy is critical.
Here’s what those STC ratings mean in practice:
- STC 40: Normal voices in adjacent office space are audible and intelligible some of the time. Raised voices and speakerphones are mostly intelligible.
- STC 45: Normal voices in adjacent office space are audible but unintelligible most of the time. Raised voices and speakerphones are partially intelligible.
- STC 50: Normal voices in adjacent space are barely audible. Raised voices and speakerphones are audible but mostly unintelligible.
A decrease from STC 45 to STC 40 isn’t just a technical downgrade, it’s the difference between muffled privacy and overheard conversations.
If your design assumes STC ratings based on 25-gauge studs, but the contractor installs 20-gauge studs, the acoustic performance may fall short of expectations. This discrepancy can have serious implications, especially in environments where privacy, comfort, or regulatory compliance is non-negotiable.
Understanding the exact construction of a partition isn’t just a technicality; it’s essential for meeting project goals and standards. When certifications such as LEED or guidelines such as FGI and CHPS are in play, every detail counts. Stud gauge is one of those details that can make or break your acoustic strategy and could mean the difference between achieving your certification or failing.
Bottom Line: If sound isolation is a priority, don’t assume, verify. In today’s building landscape, where sustainability and occupant experience are paramount, precision in design and execution is the key to success. The NV5 Technology & Acoustics group’s qualified acousticians help guide owners and design teams through complex acoustic considerations that will impact overall project success.
Julie Fischer INCE, LEED AP BD+C is a Principal Consultant in the Washington DC office of NV5 Technology & Acoustics. Julie directs our acoustics practice and is a leader and mentor for our team of acoustical consultants across North America.