Long-form guide · 8-minute read
Roof leaks. Located at the source, not the ceiling stain.
Where water shows up on your ceiling is almost never where it entered the roof. Water travels along framing, decking, and insulation before it drips. We find the actual entry point — flashing failure, cracked tile, membrane puncture, ice-dam path — using thermal imaging, drone-based aerial inspection, and infrared moisture mapping.
What is roof leak detection?
A roof leak is any water entry through the roof envelope — shingles, tile, membrane, flashing, vents, skylights, or transitions. The leak point is often metres away from where the water becomes visible inside, because water follows the path of least resistance along framing, decking, and insulation before it drips through.
On residential pitched roofs, the most common entry points are failed flashing (around chimneys, vents, valleys, and skylights), cracked or missing shingles/tiles, and ice-dam back-up at the eaves. On commercial flat roofs, it's most often membrane punctures, failed seams, or ponding water at low spots.
Detection uses thermal imaging from inside (looking up at the ceiling/roof structure for wet areas) and from outside (looking at the roof for thermal patterns indicating saturated insulation). Drones with thermal payloads have transformed commercial and high-rise detection — no scaffolding, no rope access, full-property survey in 30 minutes.
When you need roof leak detection
If you're seeing any of these signs, professional detection is warranted:
- Water stain or drip on the ceiling, especially after rain or thaw
- Mold or discoloration in the attic on the underside of the roof deck
- Wet insulation in the attic or ceiling cavity
- Cracked, missing, or curling shingles (visible from ground)
- Granule loss in gutters (sign of failing asphalt shingles)
- Ponding water on a flat commercial roof 24+ hours after rain
- Daylight visible through the roof deck from the attic
- Ice dams forming at the eaves in winter
Roof leaks compound — insulation, drywall, framing
A small roof leak that drips into insulation saturates 4–10x its visible area. Wet insulation loses its R-value, attracts mold, and rots the roof deck from below. By the time the ceiling stains visibly, you may already be looking at insulation replacement, drywall repair, and sometimes structural repair. Early detection means a flashing repair, not a re-roof.
How we detect it
- 1
Free phone consult
Describe the stain location, when it appeared, and weather conditions when it shows. Often we can predict the entry zone before we arrive.
- 2
Interior thermal survey
Thermal imaging of attic and affected ceiling area — maps the wet pathway from drip point back toward entry.
- 3
Exterior visual + thermal
Survey of the roof from outside — visual inspection of flashing, shingles, vents, skylights. Thermal scan in the morning/evening when the roof retains different heat than dry areas.
- 4
Drone aerial inspection (if applicable)
For commercial flat roofs, high-rise pitched roofs, or large residential acreage — drone-based 4K visible + thermal payload surveys the full roof in 30 minutes.
- 5
Water test (final confirmation)
If detection is inconclusive, controlled water test — spraying suspect areas while a second technician watches inside with thermal — confirms the exact entry point.
- 6
Report for roofer or adjuster
Written report with annotated photos, thermal imagery, entry-point location, and recommended scope of repair. Most roofs need a $400 flashing fix, not a $15,000 re-roof.
Detection technologies we use
Thermal Imaging
Interior and exterior thermal scans map moisture pathways and saturated insulation.
Learn moreDrone Thermal
Aerial 4K + thermal payload for commercial flat roofs, high-rise pitched roofs, and acreage properties. No scaffolding required.
Learn moreMoisture Meter
Confirms wet attic insulation and decking with quantitative readings.
Water Test
Controlled spray test as final confirmation. Two-tech coordination — one outside spraying, one inside with thermal.
Common scenarios
Single-family pitched roof
Living room ceiling stained near the fireplace. Source: chimney flashing failure 3 metres uphill from the stain. Repair: one flashing replacement ($380), interior repaint. No re-roof needed.
Commercial flat roof (warehouse)
Recurring water at a tenant's office. Drone thermal survey of the 8,000 sq ft roof identified three saturated zones — all related to a single membrane seam failure. One targeted repair instead of full re-roof.
High-rise condo (28 storeys)
Top-floor water damage. Drone thermal + visible-light survey of the parapet identified façade infiltration at a window head flashing — not the roof itself. Saved a misdiagnosed (and unnecessary) roof inspection.
Typical pricing
Typical range. Final price quoted on the free phone consult.
- Residential roof leak detection typically $300–$500.
- Commercial flat roof + drone survey typically $600–$900.
- High-rise façade investigation priced by scope (often combined with roof).
- Insurance commonly reimburses detection costs when active damage is present.
Frequently asked questions
Why is the ceiling stain not where the actual leak is?
Water that enters through the roof envelope (flashing, shingle, vent) travels along the underside of the roof deck and along framing members before it drips through the ceiling drywall. The drip point can be 2–10 metres downhill from the actual entry. Locating the entry — not the drip — is essential for a correct repair.
Can you find a roof leak without going on the roof?
Often yes — interior thermal imaging often identifies the wet pathway and the likely entry zone. For commercial and high-rise roofs, drones eliminate the need to access the roof at all. Direct roof inspection is only required when visual confirmation of the entry point is needed.
Do you do drone roof inspections?
Yes. Our drone team (drone.leak.ca) provides Transport Canada-certified pilots, 4K visible + thermal payloads, and full-roof surveys in 30–60 minutes. Standard service for commercial flat roofs, high-rise pitched roofs, and acreage properties.
Will you also fix the leak?
No — we locate and document. Repairs are done by a roofer. This separation guarantees an unbiased diagnosis (no incentive to find a leak that isn't there, or to over-scope the repair). We can recommend trusted BC roofers if you don't have one.
What's the cost difference between flashing repair and re-roof?
A flashing repair is typically $200–$800. A re-roof is $8,000–$40,000+. Most roofs we inspect have a localized issue (a single flashing failure, one cracked tile, one membrane seam) that can be repaired without re-roofing. The detection alone is often the cheapest part of the entire project.
Can you detect leaks under snow or rain?
Detection is best when the roof is dry and the conditions are stable. Light rain is workable; heavy active rain interferes with thermal. We schedule around weather conditions for best results.
Do you support insurance claims for roof leaks?
Yes — our reports are formatted for BC home and commercial insurers. We include the entry point, the path of water travel, the saturated insulation/drywall area, and the recommended scope of repair.
How do ice dams cause roof leaks?
Ice dams form when heat escaping from the attic melts snow on the roof; the melt water re-freezes at the colder eaves. Subsequent meltwater backs up behind the dam and forces under the shingles. Thermal imaging from inside the attic can identify the heat-loss patterns causing the dam — often the real long-term fix is insulation, not roofing.
Can drones see leaks through a flat roof membrane?
Drone thermal sees temperature differentials caused by saturated insulation beneath the membrane — wet insulation cools differently than dry. Patterns appear as distinct thermal anomalies. We typically survey in the early morning or evening when contrast is highest.
How long does roof leak detection take?
Residential interior + exterior survey: 60–90 minutes. Commercial flat roof drone survey: 30–60 minutes plus 1 hour analysis. Written report within 24 hours.
Related guides & services
Drone Inspection Services
Hidden Water Leak Guide
Commercial Leak Detection Guide
Thermal Imaging Technology
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Ready to talk to an expert?
Free phone consult — no pressure, no obligation. A Leak.ca technician will tell you whether you actually need detection.