THE RULES
A standard between units
In Los Angeles, walls and floor-ceilings separating dwelling units are built to an STC rating of 50, and floors also to an IIC rating of 50, under building code section 1206.
Check a standardStart
SOUND INSULATION, EXPLAINED
Keep the noise
next door.
Sound finds the easiest way through.
A solid wall helps, but a gap around an outlet box or a rigid pipe through the floor can undo it. Sound-rated assemblies in US building codes come back to a few ideas: seal the air paths, isolate what touches both sides, and fill the cavity.
STC 50between apartments
Check a standardKeep in mind
- Seal every gap
- Isolate pipes and ducts
- Stagger the outlets
- Quiet is built, not bought
THE SHORT ANSWER
Sealed, isolated,
and insulated.
The same ideas apply to walls and floors between units.
Penetrations and joints matter as much as the wall itself.
AIR PATHS
Seal the gaps
Penetrations must be sealed, lined or insulated with a permanent resilient sealant, and outlet boxes on opposite faces of a wall must be offset by 24 inches.
Four principles
HOW WALLS WORK
Isolation and insulation
Rigid pipes, ducts and vents are isolated with resilient sleeves or mounts, and the cavity gets mineral fiber insulation of R-11 or more.
See the numbersA QUICK STANDARDS CHECK
What does the
code require?
Pick a wall or floor to see the standard in one US code, Los Angeles's. STC rates how well an assembly blocks airborne sound and IIC rates impact sound on floors; for both, a higher number is better. The bar shows how demanding the standard is.
From the Los Angeles Department of Building and Safety information bulletin on sound-rated assemblies (LABC 1206). Other cities set their own codes, so check your local building department.
TWO NUMBERS WORTH KNOWING
A rating,
and a gap.
Both figures from Los Angeles's
building code guidance.
STC 50
Rating for walls and floors between dwelling units
Assemblies built to the bulletin's diagrams are considered to have STC and IIC ratings of 50. The higher the figure, the better the wall or floor performs.
STANDARD · LABC 1206
24 in
Horizontal offset for back-to-back outlet boxes
Outlet boxes on opposite faces of a separation wall must be offset horizontally by 24 inches, sealed with resilient sealant and backed by at least 2 inches of mineral fiber insulation.
OUTLETS · LADBS
The bulletin also bans wall furnaces and electrical panels in sound-rated partitions, and calls for caulking around the perimeter with a non-hardening compound.
FOUR PRINCIPLES FROM THE CODE
How quiet
walls are built.
These come from Los Angeles's guidance on sound-rated assemblies. For your own project, check with your local building department.
Step 1
Seal the air paths
Seal, line or insulate every penetration with a permanent resilient sealant, and caulk the perimeter with a non-hardening compound.
Step 2
Isolate what crosses
Separate rigid conduits, ducts, pipes and vents from the structure with resilient sleeves or mounts, or at least 1/4 inch of resilient material.
Step 3
Fill the cavity
Use mineral fiber insulation of R-11 or more, and around pipes in floor joists extend it 12 inches beyond the pipe or duct.
Step 4
Stagger the outlets
Never put outlet boxes back to back: offset them 24 inches and seal and insulate behind them.
WHEN THE NOISE IS A NEIGHBOR
Talk first,
then the city.
The EPA says that in 1981 the federal government concluded noise issues were best handled at the state and local level, and primary responsibility moved to state and local governments. So neighbor noise rules are set by your city or county.
In New York City, for example, you report noise by calling 311 or filing online, and the Department of Environmental Protection and the NYPD share enforcement of the Noise Code. Check your own city's noise ordinance for quiet hours and how complaints are handled.
Questions
Questions on the way
What does STC mean?
Sound Transmission Class, a rating of how well a wall or floor-ceiling blocks airborne sound such as voices and music. Los Angeles requires STC 50 between dwelling units; the higher the number, the better.
What does IIC mean?
Impact Insulation Class, a rating of how well a floor-ceiling resists impact sound such as footsteps. Los Angeles requires IIC 50 for floors between units, and carpet with padding is one way to reach it.
Why do outlet boxes matter for soundproofing?
Outlet boxes create weak spots in a wall. Los Angeles's code guidance says boxes on opposite faces must be offset 24 inches, sealed and backed by mineral fiber insulation.
Who regulates noise in the US?
Mostly states and cities. The EPA says that in 1981 primary responsibility for noise issues was transferred to state and local governments.
Where do I complain about a noisy neighbor?
To your city or county. In New York City, for example, you call 311 or file online, and DEP and the NYPD share enforcement of the Noise Code.
Destination