How can I tell if my roof is leaking?
Short answer. Check the attic first, during or right after a rain if you can: look with a flashlight for wet or darkened decking, damp insulation, water trails on rafters, rusty nail tips and pinpoints of daylight. Inside the house, ceiling stains, bubbling paint and musty smells near exterior walls are the usual giveaways, and outside you look for missing shingles, cracked boots and loose flashing.
A 15 minute attic check
- Go up during a steady rain or within a few hours after one. Step only on joists.
- Turn off the attic light, let your eyes adjust, and look for daylight through the decking, especially around vents, chimneys and the ridge.
- Shine a flashlight along the underside of the decking around every pipe, chimney, skylight shaft and valley. Fresh leaks look dark and shiny; old ones leave dried rings.
- Press on the insulation under any stain. Wet insulation is matted and cold.
- Look at nail tips poking through the decking. Rust around many of them across the attic points to condensation; rust at a few in one spot points to a leak.
Inside the house
Look for yellow-brown rings on ceilings, paint bubbling at the top of walls, swollen drywall tape, and a musty smell in closets along exterior walls. Check ceilings under bathrooms and attic HVAC units too, since those can mimic roof leaks.
From the ground
With binoculars, look for missing or creased shingles, cracked rubber collars on pipe boots, flashing pulled away from the chimney, and piles of granules at downspout outlets. Water stains on fascia or soffit may point to the eaves or gutters instead.
Confirming a stubborn one
Professionals use a controlled hose test: wet one small area of the roof at a time, starting low and working uphill for 10 to 15 minutes per zone, while someone watches in the attic. Starting at the top would wet everything below and hide the source.