A ceiling stain tells you water is getting in, but rarely where. The opening in the roof is often several feet up-slope, on the other side of a rafter, or above a different room.
This guide shows how to find a roof leak step by step, from the room to the attic to the roof. When a step requires walking on the roof, hand it to a roofer.
What to Do Right Now When Water Is Coming In
Limit the damage and keep everyone safe before you look for the source.
- Catch the water. Set a bucket under the drip, move furniture and electronics away, and cover what you cannot move with plastic.
- Watch for a ceiling bulge. Water pooling on drywall makes the ceiling sag, and a soaked ceiling can fall. Keep everyone out from under it, and if the sag grows, close off the room and tell the roofer when you call.
- Treat wet light fixtures as live. Do not touch a wet light, fan, or switch. Turn off that circuit at the breaker if you can reach the panel without standing in water, and have an electrician check it.
- Stay off the roof. Wet roofing is slippery, and tile breaks underfoot.
- Document the damage. Photograph the stain and any damage with the date. If you plan to contact your insurer, read your policy and call them.
If water is coming in faster than you can catch it, call for emergency roof leak repair. A roofer can protect the area with temporary tarping and sealing until it can be fixed.
Why the Stain Is Rarely Under the Hole
Water that gets past the shingles or tile usually does not fall straight down. It runs along the roof deck, a rafter, or a pipe until it reaches a low point, then drips onto the drywall and comes through at a seam or a light fixture. That is why a patch placed directly above a stain often fails. To locate a roof leak, follow the path the water took, which almost always starts higher on the roof.
Six Signs of a Hidden Roof Leak
- Stain rings on the ceiling that grow after each storm
- Peeling paint where the ceiling meets an outside wall
- A musty smell in an upstairs room after rain
- Dark stains or mold on the underside of the roof deck
- Damp or matted insulation in one part of the attic
- Daylight around a vent pipe or chimney, seen from the attic
Step 1: Write Down When and Where It Leaks
A roof leak investigation starts with notes. Measure the stain’s position from two walls so you can find the same spot in the attic, and photograph it after each storm. Then note when it leaks, since the timing is the quickest way to identify a roof leak’s likely source:
- Every rain: an open path, such as a cracked pipe boot, a missing shingle, a broken tile, or failed flashing.
- Only wind-driven rain: walls and edges, including step flashing, chimney flashing, windows, and stucco.
- Only long or heavy storms: slow saturation, such as worn underlayment under tile, an overloaded valley, or ponding water on a flat roof.
- No rain at all: probably plumbing or the AC, not the roof (see Step 5).
Step 2: Check the Attic During or Right After Rain
The trail is easiest to follow while the water is still there. Bring a bright flashlight. Step only on the joists, never on the drywall between them, and watch for roofing nails poking through the deck.
- Find the area above the stain, using your measurements.
- Look for wet or darkened wood, drips, and damp insulation.
- Follow the trail up-slope. The entry point is at or above the highest wet spot, not the lowest.
- Check vent pipes, fan ducts, the chimney, and skylight framing near the trail. In daylight, switch off the flashlight and look for light coming through.
- Mark the highest wet point with a nail tapped into the rafter beside it, and measure from there to something visible outside, such as a vent pipe or the chimney.
If there is no attic above the stain, as with a vaulted ceiling, go on to Steps 3 and 4.
Step 3: Check Where Leaks Usually Start on Your Type of Roof
Check from the ground with binoculars or from a ladder at the roof edge, starting above your attic marks.
Asphalt Shingle Roofs
- Pipe boots: the rubber collar around a plumbing vent cracks in the sun and pulls away from the pipe.
- Flashing: the metal at walls, chimneys, and skylights can rust, loosen, or lose its sealant.
- Valleys: two slopes drain into one channel, and debris there holds water against the shingles.
- Nail pops: a nail that backs out lifts the shingle above it and can wear a hole through it.
Clay and Concrete Tile Roofs
Tile roofs are common in Los Angeles, and they leak differently. The tile sheds most of the rain, but some water gets under it, and the underlayment beneath keeps that water out of the house. A cracked or slipped tile is easy to spot, but on an older roof the leak usually comes from worn underlayment near valleys, chimneys, and pipes. That is why replacing a broken tile does not always stop the leak; the usual tile roof repair is to lift the tile, replace the underlayment, and reset the tile.
Flat and Low-Slope Roofs
- Ponding water: water left sitting after a storm wears the surface and finds weak seams.
- Drains and scuppers: when debris blocks them, water backs up above the flashing.
- Seams: lapped seams in torch-down, modified bitumen, or TPO can open with age and heat.
- Parapet walls and coping: water enters through open coping joints and parapet cracks, then runs down inside the wall (see our guide to parapets and coping on LA commercial buildings).
Step 4: Run a Controlled Hose Test, Safely
If the attic did not show a clear source, a hose test is the next way to find a leak in your roof. On a dry day, one person runs a garden hose from a ladder or a low-pitched shingle roof while the other watches from the attic or the room below.
- Start below the suspected spot so the lower areas are ruled out first.
- Soak one small area for several minutes with a gentle flow and no spray nozzle, letting the water run down the roof as rain does. Spraying up under shingles or tile forces water where rain would not go.
- The person inside calls out as soon as water appears.
- If nothing shows, move up-slope to the next area. Test each side of a chimney or skylight separately.
- When water appears, the last area you soaked is the likely entry point.
Water can take a while to reach the spot where it shows, so be patient.
Where to stop: nobody should walk on a tile roof, a steep roof, or any wet roof. Tile cracks underfoot and loose pieces can slide. If the test requires any of these, call a roofer.
Step 5: Rule Out Leaks That Aren't the Roof
Not every ceiling stain comes from the roof, especially one that appears on a dry day. Check these:
- AC condensate line or drain pan: if the air handler sits in the attic, a clogged condensate line can overflow the pan when the AC runs.
- Plumbing: a supply line, drain line, toilet seal, or shower pan on the floor above.
- Windows: failed flashing or sealant around an upper window lets water run down inside the wall.
- Stucco walls: cracks let wind-driven rain get behind the stucco and into the wall.
- Chimney masonry: brick and mortar absorb water, and a cracked crown or missing cap lets it in from the top, which can look like a flashing leak.
Where the Water Shows Up and Where It Often Starts
This table will not diagnose a roof leak by itself, but it tells you where to look first.
| Where the water shows up | Where it often starts |
|---|---|
| Ceiling near an exterior wall | Step flashing, a clogged gutter, or a window above |
| Around a ceiling light or bath fan | A pipe boot or vent up-slope, or a dripping fan duct |
| Next to the chimney | Chimney flashing, the crown, or porous masonry |
| Around a skylight | Skylight flashing or the skylight’s own seal |
| Ceiling below a roof valley | Valley flashing, debris, or worn underlayment under tile |
| Top of a wall under a flat roof | Parapet coping, wall flashing, or a blocked scupper |
| Ceiling stain on a dry day | AC condensate line or drain pan, or plumbing |
When to Call a Roofer, and What We Do on a Leak Call
Call a roofer if the attic does not show the source, if finding it means walking on tile or a steep or wet roof, if the ceiling is sagging or water is near electrical fixtures, or if a repaired spot leaks again.
When you call Overhead Roofing for roof leak repair in Los Angeles, we:
- Find the source by tracing the water from inside, checking the roof, and water-testing where needed.
- Protect the house with a temporary tarp or seal if rain arrives before the repair.
- Estimate the permanent repair in writing, free, with photos you can send to your insurer. We can also meet the adjuster at the property if you ask.
Our emergency line is open 24/7 at (877) 557-7778. We offer a fast response, with same-day visits when crews are available. We are licensed, bonded, and insured (CSLB #1119699, C-39 Roofing), and our team brings 25+ years of roofing experience.
Downtown Los Angeles averages about 14 inches of rain a year, and about 12 of those inches fall from November through March, according to National Weather Service climate normals. The first storms after the dry summer are when cracked pipe boots and clogged valleys start to leak, so a roof inspection in early fall is the simplest way to catch them before November.
Questions About Finding a Roof Leak
Can I find a roof leak myself without going on the roof?
Often, yes. Measure the stain’s position from two walls, then check the attic during or right after rain and follow the wet trail up-slope to the highest wet spot. Add a look from the ground with binoculars, and many leaks can be narrowed down to one area. Go on the roof only if it is dry, low-pitched, and shingled. Nobody should walk on tile, a steep roof, or a wet roof.
Why does my roof leak only when it's windy or raining hard?
Wind pushes rain sideways and up, under shingle and tile edges and behind the flashing at walls and chimneys. Long, heavy storms keep water on the roof long enough to soak through worn underlayment, overload a valley, or pond on a flat section. Check the walls, flashing, and valleys first.
Why is my ceiling leaking when it hasn't rained?
A leak on a dry day is usually not the roof. Common causes are a clogged AC condensate line that overflows its drain pan in the attic, a plumbing leak from a bathroom above, and condensation from a bath fan duct. Check the attic unit and its drain line first, then the plumbing.
Is there a roof leak finder tool that can locate the leak for me?
Not one that replaces the basic steps. Some roofers use tools such as infrared scans or electronic leak detection on large flat roofs. On a typical house, roof leak detection comes down to tracing the water in the attic, checking the usual leak points, and running a controlled hose test.
