Mold in the Garage

Why Garages Are Different From the Rest of the House

A garage is not air conditioned, so it does not get the continuous dehumidification the rest of the home receives. In a Katy summer, garage humidity closely tracks outdoor humidity.

It also has the largest and leakiest opening in the house. Every time the door goes up, humid outdoor air replaces whatever was inside, and it condenses on cooler surfaces like the slab and the shared wall with the house.

Where the Water Comes From

Stored Belongings Are Usually the Real Problem

The mold people find in garages is frequently not on the building — it is on what is stored there. Cardboard boxes, paper, fabric, holiday decorations, and upholstered furniture are all excellent growth substrates, and they sit directly on a slab that sweats.

Anything stored in a Katy garage should be in sealed plastic bins raised off the floor. Cardboard on concrete is the single most reliable way to grow mold in a garage.

Mold on Garage Walls and Ceilings

Growth on the drywall of the shared wall usually means either a plumbing leak inside that wall or condensation on the cool side of a poorly insulated assembly.

Ceiling growth in an attached garage often traces to the attic above — a roof leak, or a bathroom fan discharging into that space.

Practical Prevention

Replace the door bottom seal when it hardens. Extend downspouts away from the garage side of the house. Get belongings off the slab and into sealed bins. Add a dehumidifier if the space is chronically damp, and keep the door closed on humid days rather than open.

If the garage floor itself is persistently damp, the issue may be slab moisture rather than air, which is a different fix.