How To Repair a Leaky Open Roof Valley and Metal Flashing

You've checked your shakes or shingles, looked for pooled water, and your roof is still leaking. It might be time to inspect other areas on your roof that often cause leaks -- open roof valleys and flashing.

­Open Roof Valleys

What You'll Need
Open valleys are relatively easy to fix with just a few simple tools like these:
  • Sheet metal
  • Wire brush
  • Metal shears
  • Roof cement
  • Trowel­

T­o repair an open valley: ­

Step 1: Inspect valley for holes all along joint. You can patch small holes with the same type of sheet metal valley is made of. Most valleys use either aluminum or copper. Using different metal to patch valley will cause corrosion.

Step 2: Clean surface of valley with wire brush.

Step 3: Cut sheet metal patch about 2 inches bigger all around than hole.

Step 4: Spread thick coating of roof cement on damaged area and press patch into place, bending it to shape of valley. Spread more roof cement over edges of patch to seal out water.

Metal Flashing

What You'll Need
Here are some tools that may come in handy for fixing metal flashing around a chimney:
  • Hammer
  • Chisel
  • Safety goggles
  • Wire brush
  • Paintbrush
  • Water
  • Cement mortar
  • Small trowel
  • Butyl rubber caulk­

Metal flashing is used to seal out water around the chimney, at vent pipes, along the valleys where two roof pitches meet, and sometimes over exposed windows. To prevent leaks at
the flashing, inspect it every spring. If you see thin spots or gaps along a flashing joint, spread roof cement over the entire joint, applying it generously with a trowel. The flashing edge should be covered completely.

At the chimney, examine the flashing carefully. Chimney flashing is installed in two parts: the base, which covers the bottom of the chimney and extends onto the roof; and the cap, which is mortared into the chimney bricks. If the mortar holding the cap flashing is crumbling or if the flashing has pulled loose, you'll have to resecure the flashing.

To resecure the flashing around a chimney:

Step 1: Pull lip of cap flashing out of mortar joint, only as far as it comes easily. Do not yank entire flashing out or pull it completely away from chimney. The less you have to separate it, the easier it will be to fix.

Roof­
An open roof valley can be fixed without professional assistance.

­Step 2: With flashing out of mortar joint, clean out old mortar with hammer and chisel, wearing safety goggles to protect your eyes. Then, being careful not to damage flashing, use wire brush on joint to clean out debris.

Step 3: Wet joint with paintbrush dipped in water. With small trowel, fill joint firmly with cement mortar.

Step 4: When joint is full, press lip of flashing into mortar, in same position it was in before. Press flashing in firmly, but don't push too far or it may pop back out and you'll have to start all over again. Let mortar dry as directed.

Step 5: When joint is completely cured, caulk around joint and over lip of cap flashing with butyl rubber caulk.

At vent pipes or metal chimneys, make sure the joint at the base of the pipe or chimney is sealed. If you can see gaps at the roof line, caulk around the base of the pipe or chimney with roof cement in a caulking gun. Vent pipes on pitched roofs usually have a protective collar; if the collar is loose, tap it back into place, and then caulk the collar base joint with roof caulk.

Learn even more about flashing -- specifically the type used around a roof's vent pipes -- in the next section.