How to Find a Roof Leak Without Going on the Roof
Most of the work of finding a roof leak can be done without going on the roof. Note exactly when it leaks, trace the water in the attic back uphill to the highest wet spot, and compare that spot with the roof's usual weak points: the flashings at walls, chimneys and skylights, the boots around pipes and vents, the valleys, and any mounts through the roof. Water often doesn't drip straight below where it gets in; it runs along the underlayment, the deck or a rafter first. And some leaks aren't the roof at all: attic condensation and plumbing or air-conditioning lines leave the same stains. The last step, testing the suspect spot with water, or with electronic or infrared methods on a flat roof, is a roofer's job on a dry roof.
This page covers pitched and flat roofs on Los Angeles houses. Tile roofs have their own detail, in why a tile roof leaks when the tiles look fine. If it's leaking right now, start with what to do when the roof leaks in a storm.
Stay off the roof
The asphalt roofing industry's manual puts safety first in its chapter on roof care: inspect the roof from the ground or through upstairs windows, with binoculars, and never climb onto a wet roof (Asphalt Roofing Manufacturers Association, ARMA). A leaking roof may also have loose or broken material on it. The job of walking it, lifting shingles or tiles and running water over it belongs to a roofer, on a dry day.
Step 1: Write down when it leaks
When a roof leaks says a lot about where. Before anyone climbs anything, note whether it leaks in every rain or only some, how long into the rain it starts, which way the wind was blowing, and whether it ever drips on a dry day. A leak that shows only in storms is covered in more detail in why a roof leaks only in heavy rain.
| When it leaks | What it usually points to | Where to look first |
|---|---|---|
| In every rain, even a light one | An opening any rain reaches: a missing or lifted shingle, a cracked or rusted flashing, a failed boot around a pipe or vent, a hole | Directly uphill of the stain |
| Only in heavy, wind-driven rain | Water pushed sideways or up under laps: flashings at walls and chimneys, skylights, the ridge and hips | The slopes and walls that faced the wind |
| Only after it has rained for a while | Water that backs up: a clogged valley or gutter, an overflowing eave, a flat-roof drain or a low spot that ponds | Valleys, gutters, eaves and drains |
| On dry days, or long after the rain | Usually not the roof: a plumbing line, the air conditioner's condensate line, or condensation in the attic | Pipes and ducts above the ceiling, and the attic's ventilation |
Two notes on the last row. Water soaked into insulation, or held on the deck, can keep dripping for a day or two after a storm, so a drip the morning after isn't proof of plumbing. And ARMA's manual warns that stains in the attic can come from condensation when the attic isn't ventilated well enough; a leak that shows up in cold weather with no rain points that way.
Step 2: Trace it in the attic
If there's an attic you can get into safely, it's the best place to find a leak, because you see the underside of the roof itself. IKO, a shingle manufacturer, sets out the precautions: walk only on the joists or trusses, never on the ceiling between them, which may not hold you, especially if it's been wet; wear gloves, goggles and a mask if the insulation is fiberglass; and don't go in at all if the insulation might contain asbestos. Take a strong flashlight.
- Start above the stain. Look at the underside of the deck, the rafters and the insulation right above it for dark or wet spots, mold, a musty smell, stains and condensation on nails.
- Follow the wet uphill. Water runs down the slope before it drips, so trace the trail up the rafters or the deck to the highest point that's wet or stained. That point is nearest to where the water gets in.
- Check the weak points nearby. ARMA's manual singles out penetrations and intersections as the places most vulnerable to water; IKO adds corners and the spots under skylights, valleys and chimneys.
- Use the light both ways. A flashlight makes wet wood shine or look darker. Then switch it off: daylight coming through the roof anywhere other than a vent marks a gap.
- Mark it for the roofer. If the spot isn't next to something easy to find from above, such as a chimney or a vent, measure its distance from the edge of the roof, as IKO suggests, so the roofer can find it on top.
- Catch the water safely. If you leave a bucket in the attic, IKO's advice is to set it on a board laid across two joists, not on the ceiling.
The best time to look is during the rain or right after it, while the trail is wet. On a 2022 job in Echo Park, the owner's photo of the kitchen ceiling bubbling in a line under a low-slope section pointed to the spot; a ceiling photographed while it's wet tells a roofer much more than the same ceiling dry.
No attic, such as a cathedral ceiling or most flat roofs? Then the timing, the ground check and the roofer's tests carry the search.
Step 3: Look from the ground
From the yard, a neighbor's driveway or an upstairs window, with binoculars, as ARMA suggests, look uphill of the stain for:
- shingles that are missing, lifted, cracked or curled, and tiles that are cracked or have slipped;
- flashing at walls and around chimneys that is rusted, bent, loose or sealed with old caulk;
- the boots or flashings around pipes and vents, and anything mounted through the roof, such as solar racking or a satellite dish;
- valleys and gutters full of leaves, and gutters spilling over the edge;
- a downspout from an upper roof emptying straight onto a lower one, which ARMA's manual says should never happen.
Photograph what you see. A picture of a stain and a picture of the roof above it, side by side, is a good start for the roofer.
Where roofs usually leak
California's residential code lists where flashing has to go, and those are the places to suspect first: where the roof meets a wall, wherever the slope or direction of the roof changes, such as valleys, and around every opening (CRC R903.2.1). The same section also calls for a flashing that turns water away where the eave of a sloped roof runs into a side wall, known as a kickout flashing, and the next one for a cricket or saddle on the uphill side of a chimney or other penetration more than 30 inches wide (R903.2.2). On a roof that doesn't drain over its edges, the code requires a drain at each low point (R903.4).
In practice, that makes the usual suspects:
- Walls. The step or continuous flashing where a roof runs along a wall, the counterflashing over it, and the kickout at the bottom. On a 2023 tile repair in Burbank, the wall junction was rebuilt with a membrane carried up under the wall flashing.
- Chimneys and skylights. The flashing on all four sides, and the cricket behind a wide chimney; a chimney in more detail is in why a roof leaks around the chimney.
- Pipes, vents and other penetrations. The boot or flashing around each one, including old ones nobody remembers; what to look for is in how pipe boots and vent flashing leak.
- Valleys. Debris that dams the water, and valley linings that are rusted or worn.
- Edges. The drip edge, and clogged gutters that spill water back behind the fascia.
- Solar mounts. Each one is a hole in the roof with its own flashing, covered in how a solar mount is sealed.
- Flat sections. Seams, drains, the base of parapet walls and the joint where a flat roof meets a pitched one, covered in flat roof repair, coating or replacement.
A leak near a solar array isn't automatically the array. On a 2023 job in Granada Hills, the owner reported a leak 18 months after the panels went on and blamed them; on the roof two days later, the water turned out to be coming through an older penetration that had nothing to do with the mounts. It was sealed on that visit, and the finding was written down for the owner. Who answers for a leak under panels is in roof warranty vs solar warranty.
What the roofer does
With the clues in hand, a roofer confirms the entry point on a dry roof:
- A close look. Lifting shingles or tiles at and uphill of the suspect spot, and checking the flashings and the underlayment under them.
- A water test. Running water over one small area at a time, starting below the suspect spot and moving up, while someone inside watches for the drip. The water runs down the roof the way rain does; spraying up under the laps can make a leak that rain wouldn't.
- Instruments on flat roofs. Electronic leak detection, which uses electrical conductance to locate leaks in a roofing membrane (ASTM D7877), and infrared imaging at night, which locates wet insulation in roofs that have insulation above the deck (ASTM C1153).
- Opening it up. When a leak has run through a season, the deck under it may be wet or soft, and only opening the roof shows it. On the Echo Park job, the section was taken off so the deck could be inspected, then rebuilt rather than patched.
How the fix is chosen, a repair at one spot or something bigger, is in repair or replace a roof. If the roof is new and leaking, start with new roof leaking after the first rain.
Frequently asked
Why isn't the ceiling stain right under the leak?
Should I go up on the roof with a hose to find the leak?
How do I find a roof leak if I don't have an attic?
Is it the roof, the plumbing or the air conditioner?
Can solar panels cause a roof leak?
When is the best time to look for a roof leak?
Related reading
Sources & methodology
Code sections, rules and figures on this page come from the primary sources below. Codes, local requirements and product terms change; each was verified October 8, 2026.
- Asphalt Roofing Manufacturers Association, Residential Asphalt Roofing Manual: Design and Application Methods, 2014 edition (Chapter 10, Flashing;…
- California Residential Code 2025, Chapter 9, Roof Assemblies (R903.2, R903.2.1, R903.2.2, R903.4)
- IKO, How to Find a Roof Leak (updated June 2, 2026)
- ASTM D7877, Standard Guide for Electronic Methods for Detecting and Locating Leaks in Roofing and Waterproofing Membranes
- ASTM C1153, Standard Practice for Location of Wet Insulation in Roofing Systems Using Infrared Imaging
We trace the leak from the attic and the roof, then fix that spot
Call (323) 844-7777. We look in the attic and on the roof, trace where the water actually gets in and repair that section, or tell you plainly if it isn't the roof at all. Have ready when it leaks and which way the wind was blowing, where it shows inside, your photos and any marks you made in the attic.
Prepared by Cali Energy, October 8, 2026. This article is for general educational purposes only and is not legal, tax, financial, engineering, or utility advice. Rates, incentives, codes, permit requirements, equipment specifications, prices, and program terms may change; figures and timelines are estimates, not guarantees. Confirm current requirements with the applicable utility, AHJ, program administrator, manufacturer, or a licensed professional. See our Content Disclaimer. Cali Energy · 19201 Parthenia St, Unit E, Northridge, CA 91324 · CSLB #1032379 (B, C-10, C-39)