For the basement apartment, the media room, and the bedroom under the kitchen. The step that has to happen before the drywall goes up.
Lehi Elite Insulation installs mineral wool and fiberglass sound insulation in basement ceilings and demising walls for homes across Lehi and Utah County, and coordinates with your finisher on the resilient channel and drywall details that turn insulation into actual soundproofing. Honest about what insulation does and does not do for noise. Free inspection, flat written price.
Takes about 30–45 minutes. No cost, no pressure.
Two kinds of noise come through a basement ceiling. Insulation is very good against one of them and only fair against the other.
Airborne sound is voices, the TV, music, the dishwasher. It travels through the air, hits the ceiling assembly, and vibrates it. Insulation in the joist bays absorbs a lot of that energy on the way through. An empty joist bay is a drum; a bay full of mineral wool is not. This is the improvement most people notice first and it is a big one.
Impact sound is footsteps, chairs scraping, kids jumping, things dropped. It goes straight into the floor and down through the joists into the ceiling drywall as vibration. Insulation in the bay barely touches it, because the sound is traveling through the wood, not the air. Stopping impact sound takes decoupling: resilient channel or isolation clips that hang the ceiling drywall off the joists so the vibration has no direct path. Adding a second layer of drywall adds mass and helps both kinds.
So the honest sequence for a basement ceiling is: insulation in every bay (our part), then decoupled drywall with added mass (your finisher's part), and sealed penetrations for can lights and ducts so sound does not leak around the whole assembly. Insulation alone gets you a quieter basement. Insulation plus decoupling gets you a basement apartment.
| Noise | Insulation alone | Insulation + decoupling + mass |
|---|---|---|
| Voices, TV, music | Noticeably quieter | Mostly gone |
| Footsteps, dropped objects | Slightly softer | Much reduced |
| Plumbing noise in the ceiling | Softer | Softer, plus pipe wrap |
| Bass from a home theater | Little change | Reduced, not eliminated |
General guidance. Results depend on the floor assembly, the finish, and how carefully penetrations are sealed.
| Factor | Mineral wool (stone wool) batts | Fiberglass batts |
|---|---|---|
| Sound absorption | Higher. Denser material absorbs more airborne sound per inch. | Good. A real improvement over an empty bay. |
| Fit | Rigid, friction-fits between joists and stays put without supports | Softer, needs wire supports or netting to stay against the subfloor |
| Fire | Non-combustible, high melting point. Often chosen for ADU separations. | Non-combustible glass, lower melting point than stone wool |
| Moisture | Water-repellent, does not hold moisture | Does not absorb, but holds water in the bay if wetted |
| Cost | Higher | Lower |
| Best fit | Basement apartments, bedrooms, any ceiling where privacy is the point | Rec rooms and offices where "quieter" is enough |
A basement apartment has at least one wall separating it from the rest of the house, usually at the stair or the shared hallway. That wall gets the same treatment as the ceiling: mineral wool in the cavities, and ideally a staggered-stud or double-stud frame from your framer so the two sides are not nailed to the same studs. We insulate whichever framing you build.
Recessed lights, duct boots, and plumbing all punch through the ceiling and leak sound around the insulation. Airtight can light covers and sealed duct boots are part of the job, and they are the same details we seal for air leakage in an attic.
Finishing a basement into a rental unit or a mother-in-law apartment is one of the most common projects in Lehi right now, in the newer subdivisions as much as the older grid. A legal unit has fire and sound separation requirements set by the building code and by Lehi City's accessory dwelling unit rules. Those are matters for your permit and your finisher, and we do not give code advice beyond that. What we do is install the insulation that those assemblies call for, in the right material, before the ceiling closes.
If the same project also needs the foundation walls and rim joist insulated, our basement insulation work gets quoted at the same visit as one job.
We look at the joist bays, what is running through them, the planned use of the room, and the finish schedule. We ask what noise you are trying to stop. About 30–45 minutes.
Ceiling bays, demising walls, material, penetration details, and any thermal work on the same visit. Flat, in writing, with notes for your finisher on decoupling and mass.
After rough electrical and plumbing, before drywall. Batts friction-fit or supported in every bay, penetrations boxed and sealed, walls filled.
Photos of every bay before it closes, so you have a record of what is behind the drywall.
Insulation in the joist bays cuts airborne sound, voices and TV, noticeably. It does much less for impact sound, footsteps and dropped objects, which travel through the framing itself. Real soundproofing is insulation plus decoupling, usually resilient channel or isolation clips under the drywall, plus mass, usually a second layer of drywall. Insulation alone is the cheapest step and the one that has to happen before the ceiling closes, so it is where every basement ceiling should start.
Mineral wool is denser and absorbs more sound per inch, and it is the usual choice for a basement ceiling where sound is the goal. Fiberglass batts are cheaper and still make a real difference for airborne noise. For a basement apartment where privacy matters, mineral wool. For a rec room where you just want the TV less loud upstairs, fiberglass is a reasonable budget choice.
Lehi City's accessory dwelling unit rules and the building code set the fire and sound separation requirements for a legal basement apartment, and those are a matter for your permit and your finisher, not something we give code advice on. What we can say is that insulated, decoupled ceilings are what make a basement unit livable for both households, and the insulation has to go in before the drywall.
Not without opening it. Insulation goes in the joist bays, and the bays are only accessible before the drywall goes up or after it comes down. If the ceiling is already closed, the options are adding mass and decoupling on top of the existing drywall, which is a finisher's job, or opening the ceiling. We will tell you which makes sense.
Between a basement and the floor above, both spaces are heated, so there is not much heat to stop. The thermal gain is small. Where the basement ceiling runs over an unheated garage or a crawl space, the same batts do real thermal work, and we spec them for both jobs at once.
We tell you what insulation will and will not do for your noise, spec the right material, and put it in writing. Flat priced.
Call (801) 348-3113Mon–Fri 7am–6pm. We'll call you back to schedule.