Leak Detection
Professional Roof Leak Detection — Downey, CA
You have a leak, but you don’t know where it’s coming from. That’s the most common way this search starts, and it’s exactly what this page is about — not selling you a product, but finding your actual leak.
Why the Stain and the Leak Are Often Not the Same Spot
On a flat roof, water doesn’t fall straight down through the deck the way it does through a wall. It runs along the underside of the membrane, follows the seams and the decking, and shows up wherever it finds the lowest point or the nearest gap. We’ve opened up roofs where the actual failure was 15–20 feet from where the ceiling stain appeared, because a corrugated metal deck underneath channeled the water sideways before it ever dripped through.
That’s the difference between a roofer who patches the wet spot and one who finds the leak. Below is how we do the second one.
Our Detection Methods
How Water Travels Beneath a Membrane
Why the visible drip and the actual entry point are often 15-20 feet apart.
Read More →Moisture Scanning for Flat Roofs
Non-invasive scanning that finds trapped moisture without cutting into the roof.
Read More →Infrared Roof Leak Inspection
Thermal imaging to spot temperature differences caused by trapped water.
Read More →Roof Water Testing (Hose Test)
A controlled test to reproduce and confirm a leak when the source isn’t obvious.
Read More →Roof Water Damage Assessment
What we check inside the building once a leak is confirmed.
Read More →Full Leak Repair Service
Once we’ve found it, here’s how we fix it.
Read More →Where We Look First
The overwhelming majority of flat roof leaks originate at a transition, not in the open field of the membrane — parapet walls, flashing, termination bars, pipe boots, skylights, HVAC curbs, and seams. See common leak causes →
Why Guessing at a Leak Source Almost Always Backfires
It’s tempting to just look at where the ceiling stain is and assume that’s roughly where the roof failed, then patch that spot and hope for the best. The problem is that a patch applied to the wrong location doesn’t just fail to fix the leak — it can actually make future diagnosis harder, since now there’s a repair attempt on the roof that has nothing to do with the actual source, and anyone inspecting later has to account for it.
This is especially true on roofs that have had more than one owner or more than one prior repair. We regularly find two or three old patch attempts on a roof before we locate the real, currently-active leak source, each one presumably made in good faith at the time but aimed at the wrong spot. Proper detection isn’t extra hassle — it’s what prevents your repair from becoming patch number four.
Detection Methods We Choose Between (and Why)
Not every leak needs every tool. A visually obvious flashing gap right above an active stain doesn’t need infrared imaging — we can often confirm that on sight. But a leak with no obvious surface cause, or one that’s been active for a while with water having spread under the membrane, benefits from moisture scanning or infrared to map the full extent before we start cutting into anything.
We pick the method (or combination of methods) based on what the situation calls for, not a one-size-fits-all checklist. For straightforward cases, a careful visual inspection paired with interior tracing is often enough. For more complex or ambiguous ones, scanning and testing earn their cost by preventing a wrong guess.
What You Can Check Yourself Before Calling
You don’t need special equipment to gather useful information before we arrive. Note exactly where the interior stain or damp spot is, relative to two walls or another fixed reference. Note when you first noticed it and whether it’s grown since. If you can safely see the roof from a window or ladder without walking on it, note any obvious ponding water, visible cracks, or debris buildup around drains — but don’t walk the roof yourself if it’s wet or you’re not experienced doing so safely.
This information doesn’t replace a proper inspection, but it does help us prioritize what to check first once we’re there, which can speed up the whole process.
Leak Detection Questions
Can you find a leak without cutting into my roof?
In most cases, yes. Visual inspection, moisture scanning, and infrared imaging are all non-invasive. We only cut into the membrane once we’ve confirmed the location and are ready to make the actual repair.
How long does a leak detection inspection take?
A straightforward case with an obvious cause can be assessed in under an hour. More complex situations involving scanning or a water test can take longer, especially on a larger roof. We’ll give you a time estimate based on what we find during the initial walk-through.
What if you can’t find the leak on the first visit?
This happens occasionally with genuinely difficult cases — intermittent leaks that only occur under specific wind and rain conditions, for example. If that happens, we’ll be upfront about it and discuss next steps, which might include monitoring during the next rain event or additional testing, rather than guessing and charging you for an unconfirmed repair.
Is moisture scanning accurate on an old, multi-layer built-up roof?
Yes, though older BUR roofs with multiple historical layers can sometimes show broader moisture readings since water may have spread between layers over time. We factor that into how we interpret the scan rather than assuming the scan alone gives a pinpoint answer on every roof type.
Do you charge extra for using infrared or moisture scanning?
The inspection itself, including whichever detection methods the situation calls for, is part of our free inspection. You’re not charged extra for us using the right tool to find your leak accurately.
Have an Active Leak?
We prioritize same-day inspections. See our emergency service →