Interior walls · Bathrooms, bedrooms & shared walls
Most interior walls are hollow. That is why you hear the bathroom fan from the living room, the TV through the bedroom wall, and everything the people next door are doing in a condo, duplex, or townhome. Cozy Walls fills those hollow walls with injection foam from inside the room — small holes, patched the same day, no drywall comes down.
Most interior jobs are done in a day. Minimum job $1,000. Erik, the owner, does every estimate himself.
Sound travels through a hollow wall the way it travels through a drum: the drywall on one side vibrates, the empty air gap carries it, and the drywall on the other side plays it back. Fill the gap and the drum goes quiet. The walls people call us about most:
No demolition. No remodel. One visit.
Erik checks the wall construction first — stud spacing, blocking, plumbing, wiring, and whether a shared wall is a fire-rated assembly that needs a different approach.
One hole per stud bay, high on the wall, sized to the injection nozzle. On a shared wall we only drill your side.
The foam goes in as a liquid and expands to fill the cavity top to bottom, around pipes and wiring, then cures in place. It doesn’t settle and it doesn’t shrink back.
Every hole is plugged and patched the same day, ready for a coat of paint. Most rooms are back to normal by dinner.
Drilled and filled from inside, then patched. These are real Cozy Walls jobs from this month.


One small hole per stud bay. This is as invasive as it gets.


Each cavity filled top to bottom around whatever is inside the wall.


Ready for paint the same day.
Filling a hollow wall adds mass and closes the air path that carries sound, and the difference is immediate: voices drop to a murmur, the bathroom fan stops being a house-wide event, and the neighbors become background instead of company. It will not make a wall silent. Sound also travels through doors, outlets, ductwork, floors, and ceilings, and a filled wall does nothing about those. If you want a recording studio, that is a different project. If you want to stop hearing every word through the wall, this is the fastest, cleanest fix there is — and it adds a little insulation value to the wall as a bonus.
Interior walls are not eligible for the Focus on Energy rebate (that program is for exterior walls), so we will never pretend otherwise. What you get is a firm written price from Erik at the estimate, a lifetime warranty on the foam that transfers when you sell, and no pressure to sign on the spot.
Shared walls are our most common interior request, and they come with a few specifics:
“The noise reduction was the first thing I noticed. I couldn’t believe the difference.”
Shawn F. · Google review
Interior walls are priced by the square foot of wall we fill. Our minimum job is $1,000; a single bathroom or bedroom wall usually sits near that minimum, and the price climbs with the number of walls. Erik measures at the estimate and gives you a firm written number that is good for 30 days. Many customers do the interior walls in the same visit as their exterior walls — ask and we will price both together.
Serving Southern Wisconsin. Erik, the owner, comes out himself.
Name, phone, best time to call — and tell Erik which wall is driving you crazy when he calls.