How to Find Where a Roof Leak Is Coming From Inside

Go into the attic on a dry day if possible. Bring a flashlight and look for water stains, dark streaks, or wet insulation. These marks often point to the leak's origin. Follow the trail of water up the roof slope, because water travels along rafters or sheathing before it drips down.

Check for daylight coming through the roofline. A pinprick of light means a hole or gap. Also inspect around vents, chimneys, and skylights, as these are common leak spots. If you see mold or rot, the leak has been active for a while, and you should act quickly.

• Check for dark stains on the wood decking
• Look for wet or compressed insulation
• Inspect around vent pipes and chimney flashing
• Search for rusted nails or fasteners
• Note any musty smell, which signals moisture

Most roof leaks happen where the roof meets something else. That includes chimneys, skylights, roof valleys, and where a dormer wall meets the roofline. Flashing, the metal or rubber strip that seals these joints, can crack or pull away over time.

Also inspect the roof penetrations like plumbing vents and exhaust fans. The rubber boot around each pipe can split. And look at the shingles or tiles themselves. A single cracked or missing shingle can let water in, especially during heavy rain or snowmelt.

• Cracked or lifted flashing at the chimney
• Missing or broken shingles near the ridge
• Damaged rubber boots around vent pipes
• Clogged or crushed gutters that back water up under the edge
• Ice dams along the eaves in winter

Some leaks are simple to fix, like replacing a single shingle or resealing a vent boot. But if the leak has been going on for a while, the roof decking or rafters may be rotted. Hidden water damage can weaken the structure and lead to mold growth.

If you cannot find the source or the leak is widespread, contact local water damage pros. They have tools like moisture meters to locate hidden dampness. They can also dry out the structure and repair the damage. For roof repairs, a roofer may be needed. Your insurance company may help, but policies vary, and your insurer decides what is covered.