My garage floor is sweating or covered with condensation. Who do I call?
Usually, start with
HVAC / building-performance professional
If moisture forms broadly on the garage floor during warm or humid conditions, an HVAC or building-performance professional commonly evaluates temperature, humidity, ventilation, and condensation conditions in the space.
Change course if
The moisture appears after rain rather than humid weather
Drainage or waterproofing expertise may be relevant when exterior water conditions appear connected.
The wetness is localized near plumbing or equipment
A plumber may be relevant when a leak source is plausible.
The slab stays damp even when indoor humidity is low
A concrete or moisture-testing professional may be relevant to evaluate moisture associated with the slab.
Who handles what
HVAC / building performance
Evaluates humidity, surface temperature, ventilation, and conditions that can produce condensation.
Drainage / waterproofing
Evaluates exterior water entry when the pattern is connected to rain or site water.
Concrete / moisture testing
Evaluates moisture conditions associated with the slab when surface condensation does not explain the pattern.
What might be happening
Condensation can form when warm, moisture-laden air contacts a surface cool enough for water to condense. A garage slab can remain cooler than the surrounding air, particularly during weather transitions. Similar-looking dampness can also have other sources, so the pattern matters.
Useful things to notice
Weather when it happens
Warm humid days following cooler conditions are useful to note.
Whether the whole slab is affected
Broad surface moisture can look different from a localized leak or entry point.
Whether metal objects or other cool surfaces also collect moisture
Condensation elsewhere in the garage can provide useful context.
Before you call
Note outdoor weather, indoor garage temperature if known, and whether doors were open or closed. Photograph the distribution of moisture across the floor.
Before you fix the visible symptom
Do not assume a floor coating or surface sealer will address the cause of recurring moisture. Establishing whether the water is condensation or another moisture source is useful before changing the floor finish.
References
U.S. Environmental Protection Agency. Moisture Control Guidance for Building Design, Construction and Maintenance.
U.S. Environmental Protection Agency. Mold Course, Chapter 9: Prevention.
Door & Access Systems Manufacturers Association. Technical Data Sheet 195, Garage Doors and Condensation.