How to Find a Roof Leak From Inside the House
Water does not fall straight down from a hole in the roof. It hits the underside of the decking, runs along a rafter, follows the top of the ceiling drywall and drops wherever it finds a seam or a light fixture, which can be ten feet from where it came in. That is why the stain over the hallway is so often from a pipe boot over the bathroom. If you can get into the attic, you can usually find the source yourself, or at least narrow it down enough to save an hour of a roofer's time.
What you need
A good flashlight, a phone for photos, a tape measure, a dust mask, and a board or two to kneel on if the attic has no floor. In most Schaumburg ranches and split-levels the attic hatch is in a hallway or bedroom closet, and the attic is a crawl — 3 to 4 feet at the ridge. Go in daylight, and ideally during or just after a rain.
Step one: find the wet spot from below
Before you go up, measure from the stain to two walls of the room and note it. In the attic, find that spot on the underside of the deck. The insulation there will be wet or matted, the joists stained. Now look up and uphill.
Step two: trace it uphill
Water runs down. Follow the stain on the underside of the roof deck or along the rafter uphill until it stops. That top point is within a foot or two of where the water is getting in. Look for daylight, a nail with a rust ring around it, a dark trail down from a penetration, or a plywood seam that is delaminating.
What it usually is, in order
Pipe boots. The rubber collar around the plumbing vent over the bathroom or kitchen. After 10–15 winters it cracks where it meets the pipe. In the attic, it is the vertical pipe with a water trail down it. About $300–$450 to replace.
Chimney flashing. The most common leak on the 1960s–70s brick-chimney houses in Weathersfield and the Hoffman Estates parcels. Water trail on the framing around the chimney chase, worst on the uphill side, where snow piles against the brick with no cricket to divert it.
Valleys. Where two roof planes meet. Look for a stain running along the valley rafter. Closed-cut valleys without ice-and-water shield leak from the bottom third up, usually after an ice dam sat in them.
Skylights. A stain around all four sides of the skylight shaft means the curb flashing; a stain at one bottom corner often means the unit's seal or condensation. The skylight and chimney flashing work is standard repair territory.
Ice dam damage. A stain right at the eave line, above the exterior wall, and nowhere else — and it only shows up in February. That is water backing up under the shingles behind an ice dam. It is not a hole; there is nothing to find uphill.
Nail pops and exposed nails. A single rusty nail with a drip ring around it. Cheap fix, easy to miss.
Wall and dormer step flashing. On split-levels where the upper roof meets the wall of the upper level, and on any dormer. Stains down the wall framing on the inside.
The flat-to-pitched transition. On a split-level, water on the ceiling of the family room or garage with a stain at the exact line where the low-slope roof meets the shingled one. See flat roofs.
A quick attic checklist for Schaumburg houses
- Wet or stained spot on the deck: measure and photograph.
- Trace uphill to the highest point of the stain.
- Nearest penetration: pipe, chimney, skylight, exhaust fan cap, satellite mount.
- Nearest valley or wall.
- Daylight anywhere, especially at the ridge and gable ends.
- Rusty nail points: a few is normal; a cluster is a leak or condensation.
- Frost or drips on the nails in January with no rain: that is condensation from a warm, humid attic, not a roof leak. Bath fans venting into the attic cause most of it.
- Insulation depth and whether the soffit vents are blocked. Not a leak, but the reason the ice dams form.
Staying safe in the attic
- Step only on the joists or on boards laid across them. The drywall between joists will not hold your weight.
- Roofing nails come through the deck overhead; wear a hat and move slowly near the eaves.
- Keep clear of wiring and junction boxes, and don't pull insulation off them.
- Don't stay up long on a warm day. Attics heat up fast, even in September.
- If the insulation is gray-brown and pebbly, it may be vermiculite, which can contain asbestos. Don't disturb it; have it tested first.
A hose test, with a helper
If the attic does not show an obvious source, a hose test can narrow it down. One person stays in the attic with a flashlight. The other runs a garden hose on the roof from a ladder at the eave — never by walking a steep or wet roof. Start low and work up, soaking one area for several minutes before moving: the bottom of a valley, then the downhill side of the chimney, then its sides, then the uphill side, then a pipe boot. When water shows up inside, the last area soaked is the likely source. It is slow, and it only works above freezing. If you can't reach safely from a ladder, leave it for the roofer, who can do the same test from the roof.
Slow leaks that are easy to miss
- Insulation that is darker or flattened in one spot.
- A musty smell in a closet under the roof.
- Paint bubbling at the top of an exterior wall.
- Mold spots on the underside of the deck near one penetration.
- Water marks or rust on the trim of a ceiling light.
When it is not the roof
Three things get mistaken for roof leaks. A bath fan ducted into the attic instead of outside, dripping condensation back through the ceiling in January. A plumbing vent or supply line running through the ceiling. And on second-floor ceilings under a flat-roof section, an AC condensate line. If the stain grows in dry weather, it is plumbing or condensation.
What to do with what you found
Photograph the attic stain and the top point of the trail, note the nearest penetration, and tell the roofer that when you call. Add when it shows up — every rain, only wind-driven rain, or only with snow on the roof — and the roof's age and layers if you know them. That is often enough for the right parts to come on the first visit. Roof leak repair in Schaumburg is priced by what the fix is, and knowing it is the pipe boot over the second bathroom versus "somewhere on the back" is the difference between a same-visit $350 fix and a diagnostic visit first. If you cannot get into the attic, or the roof is icy, do not go on the roof; call. The roof repair page covers each of the fixes above and what they cost, and if the roof is over 20 years old the repair-or-replace guide is the next thing to read.
Common questions
Can a roof leak show up in only one room? Yes, and most do. One failed boot, one flashing or one valley usually shows up as one stain, often a few feet from where the water got in.
Why does the stain appear days after the rain? Water can soak into insulation and decking and travel along the framing before it reaches drywall. A late stain is still a leak; trace it the same way.
Should I cut into the ceiling to find it? Usually not. The attic shows far more. Only open a ceiling to drain a bulge, with a bucket underneath.
Need roof work in Schaumburg?
Call for a free estimate. Mon–Sat 7am–7pm.