Spotting Water Leaks & Moisture

The camera can’t see water — it sees what water does to temperature. Damp drywall cools itself by evaporation the same way sweat cools you, and wet material holds temperature longer than dry material as the room changes. The result is usually an irregular cool blotch with soft, feathered edges, often spreading from a plumbing line, a ceiling below a bathroom, or a roof penetration.

Shape is your diagnostic. Water follows gravity and soaks outward, so moisture patterns are organic — amoebas, trails, and rings. Compare that with the crisp rectangles of insulation gaps and the directional streaks of air leaks, and you can usually tell the three apart at a glance.

Work the high-probability zones: ceilings directly below bathrooms and laundry rooms, around skylights and chimneys, under window sills, inside sink cabinets, behind the fridge and dishwasher, along the bottom edges of exterior walls, and any ceiling stain that "dried up years ago."

Timing multiplies your odds. Scan ceilings within a day of rain or active snowmelt to catch roof and flashing leaks in the act. For supply-line and drain leaks, run showers and fixtures for ten minutes, then scan the ceiling below — an active drip blooms on the thermal while you watch.

After a snow, the roof itself becomes a diagnostic: from outside in early morning, bare warm streaks through an otherwise snowy roof reveal exactly where heat is escaping the attic (and where ice dams will form later). Uneven melt lines along the eaves point to insulation gaps at the top plate of the walls below.

On siding, vertical dark trails below windows after rain mark where water is getting past the sill flashing — worth a look long before it ever shows up on an interior wall.

The same physics makes the camera the perfect tool for in-floor heat: run the system for thirty minutes and every loop paints itself across the floor. Even heating means a healthy system; a dark serpentine gap means a blocked or airlocked loop. It’s also the civilized way to find hot-water pipe runs before you drill into a slab or wall.