Homes · Strata · Commercial roofs
The skylight gets blamed. We find out if it's guilty.
Stains around a skylight have four possible authors: the flashing, the curb connection, the unit itself — or condensation impersonating a leak entirely. Replacing the skylight on a guess is the most expensive way to learn which one you had. Thermal imaging plus layer-by-layer water testing produces the verdict first, so the repair is the right one, once.
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The usual suspects
- Flashing laps and counter-flashing at the curb
- Curb-to-membrane connection aging out
- Unit frame corners and weep-path seal failures
- Uphill roof defects draining down to exit at the skylight
- Condensation from interior humidity, impersonating a leak
- Original installation details that never met the spec
How the verdict gets reached
- 1
History & timing
When it shows — which storms, which seasons, which conditions — usually rules half the suspects out before testing begins. Condensation and leaks keep different calendars.
- 2
Interior survey
Thermal imaging and moisture mapping bound the wet zone and trace it to its arrival point at the assembly — which is not always the skylight everyone's staring at.
- 3
Controlled water testing
Calibrated spray isolates one layer at a time — flashing, curb, unit — from the bottom up, with the interior monitored. The layer that reproduces the leak is the layer that's guilty.
- 4
Verdict report
Entry point, path, and evidence — scoped for the right trade: roofer for flashing, glazier for unit seals, or a ventilation conversation if condensation was the author all along.
Owners ask
Is it a skylight leak or just condensation?
The most important question, and the one that wastes the most money when guessed. Condensation appears on cold clear nights and heating-season mornings, tracks interior humidity, and shows on the glass and frame's room side. A true leak tracks rain and wind events and arrives from the assembly. Thermal imaging, moisture mapping, and timing analysis separate them definitively — and roughly half of 'leaking skylights' turn out to be condensation problems with a ventilation fix, not a roofing one.
Where do skylights actually leak from?
Rarely through the glass. The real entry points, in order: flashing laps and counter-flashing at the curb, the curb-to-roof membrane connection, the unit's own seals at frame corners and weep paths, and — frequently — uphill roof defects whose water travels down to exit at the skylight, framing it for someone else's crime. Controlled water testing isolates each layer in sequence, so the repair targets the actual entry.
The roofer resealed it twice and it still leaks. Why?
Because resealing treats every suspect at once and proves none of them — and if the true entry is an uphill membrane lap or a frame corner the caulking never reached, the leak survives every tube of sealant. Step-tested water isolation finds the layer that actually fails; the third repair is the one based on evidence, which is why it's usually the last.
Can you test skylights that are hard to reach?
Yes — testing rigs and access methods cover most residential and low/mid-rise commercial skylights, and for large arrays or difficult roofs our drone thermal capability surveys from above first, flagging which units and flashings deserve hands-on testing. Interior-side thermal and moisture work needs only a ladder and the room below.
Roof leak detection·Window & door leaks·Attic water damage·Envelope leak detection
Verdict before repair. Every time.
Free phone consult — your stain's timing usually tells us half the story on the call.