How to Find a Roof Leak From Inside the House
The stain on the ceiling is the end of the story, not the beginning. On a 10/12 roof in Windward, water that gets in at a pipe boot near the ridge can run twelve feet down a rafter before it soaks through the drywall, so the wet spot in the hallway tells you almost nothing about where the roof is open. The attic does. Here's how to look, what you're looking for, and what each finding usually means.
Before you go up
Wait for a rainy day or the morning after one — in summer that means the afternoon after a thunderstorm. A dry attic in a dry week hides most leaks. Take a bright flashlight, a phone, and a tape measure. Wear shoes with grip and step only on the ceiling joists or the walkway, never the drywall between them.
If you have a bonus room over the garage, the attic is usually split into sections with kneewall access doors; the leak is often in the small triangular attic behind the kneewall, which nobody has looked in since the house was built.
What you're looking for
Water stains on the underside of the decking. Dark rings or streaks on the OSB. Fresh ones are dark and damp; old ones are pale brown with a dark edge. Follow a streak uphill — it will lead to the rafter it ran down, and from there up to the entry point.
Wet or rusted nail tips. Thousands of shingle nails poke through the decking. If a cluster of them is rusty or dripping and the wood around them isn't stained, that's often condensation rather than a leak — more on that below.
Daylight. Turn the flashlight off and let your eyes adjust. Pinholes of light around a pipe or at the ridge are open holes.
Wet or compacted insulation. Blown insulation that has settled into a dark dish is where water has been landing.
Mold or a musty smell. Long-running leak, or a ventilation problem.
The six places Alpharetta roofs leak
Once you have a location in the attic, measure from a landmark — the chimney, a gable end, the ridge — so you can find the same spot on the roof. Then think about what's above it.
- Pipe boots. A rubber collar around each plumbing vent. In Georgia sun they crack around year 10–15. Look for the stain directly around a vent pipe near a bathroom. Cost to fix: $250–$450.
- Chimney flashing. Stain on the uphill side of the chimney, where water piles up. On the 1990s brick homes here the flashing was often a single strip caulked to the brick. Cost: $600–$1,500 to rebuild with step and counter-flashing.
- Valleys. A long stain running down where two roof planes meet. Pine needles collect in valleys and hold water against the shingles. Cost: $500–$1,200 to re-lay with membrane.
- Skylights. Stain on the downhill corners of the skylight well. Usually the flashing kit, not the glass. Cost: $400–$900.
- Wall and dormer step flashing. A stain along the line where a dormer or a second-story wall meets the roof below. On hardcoat stucco homes, check the bottom corner of the wall — a missing kick-out flashing sends water into the wall cavity. Cost: $450–$1,100.
- Ridge and ridge vent. Water at the very peak, especially after a windy storm. The ridge cap shingles or the vent were lifted. Cost: $350–$900.
If the stain is in the middle of a slope with nothing above it, look for a nail pop — a nail that has backed out and lifted a shingle — or a shingle that cracked. Small and cheap to fix, and hard to find without walking the roof.
When it isn't a leak
Two things get mistaken for roof leaks in Alpharetta every winter.
Condensation. Warm, humid house air gets into the attic through recessed lights, the attic hatch, and unsealed bath fans, hits the cold underside of the decking on a January night, and drips. Rusty nail tips everywhere, frost on the decking on the coldest mornings, and damp insulation with no stain trail. The fix is air sealing, venting bath fans outside instead of into the attic, and proper ridge and soffit ventilation. A roofer who quotes shingle work for this is guessing.
HVAC and plumbing. Most Alpharetta two-stories have the air handler in the attic. A clogged condensate line or a sweating refrigerant line drips onto the drywall and looks exactly like a roof leak, except it happens on hot dry days. A stain that appears in August drought is the air handler, not the roof.
What to do with what you found
Photograph the stain, the wet spot, and anything you can see above it. Note the weather when it happened. Then call a roofer. One who gets that information can walk straight to the problem instead of hunting, and you can often get a repair price the same visit. The roof repair page explains how a roofer confirms it from the roof side — usually with a hose test if the attic didn't settle it — and the inspection page covers what gets checked if you'd rather have the whole roof looked at while someone is up there.
Staying safe up there
Attics in Alpharetta two-stories are often hot, cramped and full of things that can hurt you. A few rules:
- Go up in the morning in summer. By afternoon an attic under a dark roof can be dangerously hot.
- Step only on joists or a walkway board. A foot through the drywall is a costly repair and a bad fall.
- Watch for roofing nails poking through the decking overhead. A hat helps.
- Don't touch wiring, and stay clear of junction boxes near wet spots.
- Tell someone you're going up, and bring your phone.
If the access is a pull-down ladder in a closet ceiling and the attic is packed with insulation, it may be smarter to let a roofer do this part.
Keep a leak log
Leaks that come and go are the hardest to find. A simple log makes them easier. Each time you see water, write down the date, how long it rained, how hard, and which way the wind was blowing. Note where the drip showed up and photograph it. After three or four entries a pattern usually appears. A leak that only shows in a west wind points to the west-facing flashing. One that only shows after hours of steady rain points to a valley or a worn spot that slowly soaks through. Hand the log to the roofer; it can save an hour of searching.
How to find a roof leak with a hose
If the attic didn't settle it, a hose test usually does. It takes two people: one on the roof with a garden hose, one in the attic or the room below. Start low on the roof, below the suspected spot, and run water on one small area for several minutes. Move uphill a few feet at a time. When the person inside sees water, you've found the section. On a steep roof the person on top should be a roofer with fall protection, not a homeowner.
Common questions
Why does my roof leak only sometimes?
Usually wind. Rain driven sideways gets under flashing and lifted shingles that shed straight-down rain just fine. A leak log will show it.
Should I cut into the ceiling to look?
Usually not. The attic shows more and costs nothing to fix afterward. Only open drywall if it's sagging with water, and then just a small drain hole over a bucket.
Can a roof leak far from where the stain is?
Yes. Water runs along rafters and the top of the drywall before it soaks through. Ten feet or more is common on a steep roof.
One more thing: don't put a bucket under it and wait for spring. The November-to-March rain in Georgia is the wettest stretch of the year, and a $400 boot leak in October is a $1,500 decking and drywall job by February.
Need roof work in Alpharetta?
Call for a free estimate. Mon–Sat 7am–7pm.