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 who gets that information can walk straight to the problem instead of hunting, and you'll get a repair price the same visit. Our roof repair page explains how we confirm it from the roof side — usually with a hose test if the attic didn't settle it — and the inspection page covers what we check if you'd rather have the whole roof looked at while we're up there.
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.