Turning a garage into a living space is a smart way to add a bedroom, office, or studio to your Los Angeles home.
But if you do not plan for soundproofing from the start, traffic noise, neighbors, and even sounds from inside your own house can make the new room feel less like a retreat and more like an echo chamber.
Thoughtful sound control protects your investment and makes your converted garage feel truly finished, not just “good enough.”
Below, we break down how Sound Transmission Class (STC), insulation, and quiet design strategies work together so you can make informed decisions before drywall goes up.
Understanding the Basics of Soundproofing in Garage Conversions
Most garages were never designed as living space. Walls may be thin, doors usually leak sound and air, and the slab floor can carry vibration from vehicles, footsteps, and nearby streets. When you convert that shell into a bedroom, office, or media room, you need a different level of acoustic performance.
There are two main types of noise to think about:
- Airborne noise: Voices, TV, music, traffic, barking dogs.
- Impact noise: Footsteps above, doors slamming, heavy items dropping, vibration from mechanical systems.
Effective soundproofing in a garage conversion is built around four core principles:
- Mass
Heavier materials, like multiple layers of 5/8 inch drywall or concrete, make it harder for sound waves to pass through. - Decoupling
Separating layers of structure so vibrations do not transfer directly from one side of a wall or ceiling to the other. - Absorption
Filling cavities with insulation to reduce the energy of sound waves inside walls and ceilings. - Sealing
Closing gaps at outlets, around doors and windows, and at the floor and ceiling line so noise does not sneak through the weakest point.
Before you finalize design plans, decide how the space will be used. A guest room on a quiet street has different needs than a drum practice room or a home office next to a busy road. That use case will drive your STC targets and the level of construction detail you choose.
What is STC? Setting Sound Transmission Class Targets for Garage Conversions
Sound Transmission Class, or STC, is a rating that describes how well a building assembly blocks airborne sound. It is a single number that summarizes performance across a range of frequencies. Higher STC means better sound isolation.
Some useful reference points:
- A typical interior wall in an older home may be around STC 30 to 35, where normal speech is clearly understood from the next room.
- Around STC 40 to 45, speech is muffled but still audible.
- Around STC 50 and above, you generally cannot hear normal speech, and loud sounds are reduced to a faint murmur.
For multi family buildings, modern codes often require walls and floors between units to reach around STC 50, because that is the level where noise complaints drop significantly and most people feel adequately protected from neighbors.
For a garage conversion in a single family home, good practical targets are:
- Bedrooms or home offices: Aim for wall and ceiling assemblies around STC 50 or better where they separate the converted garage from loud areas like streets, driveways, or main living spaces.
- Studios or hobby rooms with louder activities: Target STC 55 or higher where possible, especially on shared walls with bedrooms or neighbors.
It is important to remember that the assembly is only as strong as its weakest link. If you design a wall at STC 55 but install a thin, hollow core door with poor seals, real world performance will be closer to that door’s rating. Doors, windows, and penetrations all need to support your STC goals.
The Role of Insulation in Achieving Effective Soundproofing
Insulation is one of the most cost effective tools in a soundproofing plan. While it does not block all noise on its own, it dramatically improves performance when combined with mass and decoupling.
Types of insulation for garage conversions
Common options for wall and ceiling cavities include:
- Fiberglass batts
Widely available and affordable. Standard fiberglass provides decent sound absorption and good thermal performance when properly installed and fitted tightly. - Mineral wool (rock or slag wool)
Denser and heavier than fiberglass, which helps dampen sound more effectively. It also offers high fire resistance and strong thermal performance. Many builders prefer mineral wool in sound sensitive partitions because of its combination of density and workability. - Dense pack cellulose
Blown-in cellulose creates a dense, continuous fill that absorbs sound energy and reduces air currents in wall cavities. Proper installation is made by trained crews and is often used in retrofits.
For garage conversions, the priority is usually to:
- Fill all stud and joist cavities fully
Gaps, voids, or compressed batts reduce both acoustical and thermal performance. - Prioritize noise sensitive boundaries
Use higher performance materials, such as mineral wool, on walls facing the main house, bedrooms, or neighboring properties, and on ceilings if there is living space above. - Combine insulation with mass and decoupling
Insulation works best when paired with heavier drywall and decoupled framing. On its own, it will not stop bass-heavy music or traffic rumble, but it significantly improves overall STC when used inside well designed assemblies.
Think of insulation as the absorber inside a soundproof “sandwich.” It is a key ingredient, but not the entire recipe.
Quiet Design Strategies: Walls, Ceilings, Doors, and Windows
Once you understand your STC targets and have chosen an insulation strategy, the next step is designing the wall and ceiling assemblies that will deliver real world performance.
Walls and ceilings
For many Los Angeles garage conversions, a good wall or ceiling system might include:
- Decoupled structure
Options include staggered studs, double stud walls, or resilient channels and sound isolation clips that separate the drywall from the framing. This decoupling breaks the direct path that vibrations would otherwise follow. - Cavity insulation
Fill the separated framing cavities with mineral wool or high density fiberglass. This absorbs sound energy and boosts STC. - Multiple layers of drywall
Using two layers of 5/8 inch drywall on the room side of the wall or ceiling increases mass and helps block noise. Some homeowners also choose to use a viscoelastic damping compound between layers for extra performance. - Airtight construction
Seal all seams, joints, and penetrations with acoustical sealant, including around electrical boxes, top and bottom plates, and any mechanical penetrations.
For ceilings under living space, this kind of assembly helps control both airborne noise from conversations and impact noise from footsteps or chairs moving above.
Doors
Doors are often the weakest link in a soundproofing plan, especially in garage conversions where the original door may have been a thin hollow core or an old exterior unit with poor seals.
For quiet performance, consider:
- Solid core doors rather than hollow core.
- Full perimeter seals and an adjustable threshold or door bottom to cut down on air gaps.
- Ensuring the door’s STC rating is close to or higher than the wall assembly so it does not become the dominant path for noise.
Even a great wall is only as quiet as the doorway that punches through it.
Windows
If your garage conversion adds or reuses windows, they need to support your acoustic goals:
- Double glazed or laminated glass units typically offer significantly better sound control than single pane windows.
- Higher performance double pane windows and specialized configurations can reach noticeably higher STC values than standard units.
- Proper installation and air sealing around the frames are as important as the glass itself. Small leaks can have an outsized effect on perceived noise.
Treatments, Finishes, and Budget: Getting the Most From Your Investment
Once the structure is sound, interior finishes and furnishings can fine tune how the room feels and sounds.
Acoustic treatments and finishes
Remember that soundproofing (keeping noise from entering or leaving) is different from acoustic treatment (making the room sound pleasant on the inside). Both matter.
You can improve room acoustics with:
- Area rugs and acoustic underlayments on top of the slab to reduce footfall noise and echo.
- Fabric covered acoustic panels on walls or ceilings, especially in offices and studios where clarity is important.
- Soft furnishings such as upholstered furniture, curtains, and bookcases filled with books and décor, which help break up reflections.
These treatments will not dramatically change STC ratings, but they make the space feel calmer and more controlled.
Planning your budget and phasing
Soundproofing decisions are most cost effective when they are made while the garage is still open and down to the studs. It is far more expensive to come back later to add resilient channel or extra drywall once finishes are installed.
As you plan your project:
- Invest first in the assemblies you cannot easily touch later: framing, insulation, clips, channels, and extra drywall layers.
- Match the level of sound control to the room’s purpose so you are not overspending where it is not needed, or underbuilding where privacy matters most.
- Coordinate soundproofing with other upgrades like HVAC, electrical runs, and lighting so penetrations are minimized and properly sealed.
Not sure how to budget for design fees? Check out our breakdown of how much an architect costs for a remodel in Los Angeles. Understanding your design and consulting costs up front makes it easier to decide how much of your overall budget you can dedicate to higher performance wall and ceiling assemblies.
When you work with an experienced garage conversion contractor, they can help you balance performance, cost, and constructability so you get real acoustic benefits without blowing the budget.
Transform Your Garage Conversion With Effective Soundproofing
A quiet, comfortable garage conversion does not happen by accident. It is the result of setting clear STC targets, choosing the right insulation, and designing walls, ceilings, doors, and windows that work together as a system. When you combine smart structure with thoughtful finishes, your new space feels private and serene, even in a busy Los Angeles neighborhood.
If you are planning a garage conversion and want to get the soundproofing right the first time, partnering with a team that understands both construction and acoustics will pay off every day you use the room.