A shared wall is rarely a sealed wall

In a typical attached garage, the wall and ceiling between the garage and the house contain gaps around wiring, plumbing and ducts. Warm indoor air tends to rise and escape upward while cooler garage air is drawn in at lower levels, so a smell in the garage can easily show up in a bedroom above it or in a hallway next to the door.

At turnover the garage is often the last place anyone looks. A tenant may have left stored boxes, damp cardboard, old paint cans or items that were kept in the space through a wet season. Even when nothing is obviously spoiled, the concrete floor can hold stains and smell from years of use.

The aim is to find out whether the source is in the garage, whether the pathway into the house is open, and which of those two to fix first.

When a smell in the house is traced to the garage, resist the urge to use the living space as the place to deal with it. Fix the source first, then close the gaps, and only then judge whether the rooms next to the garage still need attention.

Checking the pathway

  1. Start in the garage

    Remove everything that does not belong, bag damp cardboard, and sweep the floor to see what is underneath.

  2. Check the house door

    Look at the weatherstripping and the threshold. A worn seal lets air move freely between the spaces.

  3. Look for penetrations

    Check where pipes, wires and ducts pass through the shared wall or ceiling and note any visible gaps.

  4. Inspect any ductwork in the garage

    A return or supply duct that runs through the garage can pull garage air into the whole house.

  5. Close and recheck

    After cleaning, seal what can be reached and smell the adjoining rooms the next day.

Places smell tends to enter

House door
Worn weatherstripping and gaps beneath the door
Ceiling above the garage
Light fixtures, access hatches and wiring openings
Plumbing walls
Gaps around pipes that run between the spaces
Ductwork
Leaky seams on runs that cross the garage

Common questions

Does sealing gaps require a contractor?

Small gaps can often be closed by a handy person using materials made for the purpose. Gaps near ducts or fire-rated walls deserve more care, and a qualified tradesperson can advise.

General information for Aurora, not a quote or professional advice. In an emergency, call 911.