Why bathrooms and kitchens are the usual entry points
Wood-frame garden and mid-rise buildings in the south metro typically run plumbing in walls that line up floor to floor. Each time a plumber or installer opens a wall or replaces a vanity, they cut holes for pipes. Those holes are often larger than the pipe, and the gap is hidden by the cabinet back or a trim ring.
An exhaust fan in a bathroom or a range hood that vents outside lowers the pressure in that room slightly. Air then comes from wherever it can, and an open chase is an easy path. The result is that the unit running its fan most often is the one that smells the neighbors.
Common gaps and how they are usually closed
| Location | Typical gap | Common fix |
|---|---|---|
| Under kitchen and bath sinks | Oversized holes around drains and supplies | Fire-rated sealant or foam suited to the wall, plus escutcheons |
| Behind toilets | Gap around the supply line and at the wall base | Escutcheon and sealant around the line |
| Tub and shower walls | Open access panel or loose trim around the valve | Gasketed access panel, sealed valve trim |
| Washer box | Open back of the recessed box | Seal the box perimeter and any open knockouts |
| Electrical outlets on shared walls | Box edges and cable entries | Foam gaskets behind cover plates |
| Bath fan housing | Gap between housing and ceiling drywall | Seal the housing flange to the ceiling |
Working through a stack
Map the stack
Identify every unit that shares the chase, above and below. Odor can skip a floor.
Open and look
Pull vanity contents, toe kicks and access panels in each unit and photograph what you find.
Seal from the source side first
Seal the smoking or cooking unit where possible, then the complaining unit, then the units in between.
Retest with the fan running
Ask the resident to run the bath fan for twenty minutes in the evening and report back for a week.
Common questions
Do we need entry to every unit in the stack?
Usually yes, with proper notice under the lease and Colorado law. Plan the work as a single project so residents get one notice and one visit.
Will sealing fix it completely?
It often reduces it a great deal. Heavy indoor smoking on the other side of a wall can still be noticed, which is why smoking policy and sealing work together.
General information for Centennial, not a quote or professional advice. In an emergency, call 911.