Repairing Flashing

If you can't find obvious damage to your roof, such as missing shingles or shakes, you can usually trace leaks to flashings or valleys.

Roof Valleys
Leaks in valley flashing usually occur where water backs up in the valley due to obstructions. The water flows over the edges of the flashing and runs under the rooding material. Fix this by clearing the valley of debris, which can act like a dam to back up water.

Next make sure that the roofing material in the valley is cut in a smooth, straight line.
If any of the material such as underlayment or a shingle, sticks out of the valley and under the shingles. To ensure against valley leaks, carefully raise composition shingles where they meet the valley flashing and coat the area with roofing cement. Then run a bead of caulk down the valley flashing right net to the shingles. On wood shingles or shakes, just run a bead of caulk along the edges where they extend onto the valley flashing.

A break in the metal flashing itself can cause a leak. If you find a break, repair it with aluminum patching tape and roofing cement. Cut off a length of tape to amply cover the hole, peel off the backing stick the tape in place and cover it with roofing cement.

Vents
Leaks occur around vent pipes when the caulk or roofing cement has shrunk or cracked. A new bead of cailk is the cure.


Inspect for damage to the roofing surface around and above the vent pipe before beginning.  A crack in a shingle or tile will let water run under the metal flashing and down the vent pipe. Slightlu raise the roofing cement under it.

Also see if the roofing material around the flashing is cut smoothly. If part of a composition shingle, wood shingle, or shake protrudes slightly t may divert water under the flashing. Trim the problem shingle with aviation snips or heavy-duty shears, then caulk.

On tile roofs, check the concrete grout around vents. you can seal cracks temporarily with caulk, but the mortar should be chiseled out and replaced with a new coat. 


Chimney Flashings
Flashing around a chimney consists of base and cap parts. Leaks frequently start where the cap flashing sets into mortar between the bricks. If there appear to be only one or two spots of loose mortar between the bricks. If there appear to be only one or two spots of loose mortar, scrape it out and fill the gap with vinyl rubber caulk, which adheres well to masonry.

If the mortar is in poor condition, break it all out with a chisel and remove the cap flashing. For the patching material, use premixed mortar or make your own with 1 part cement and 3 parts sand. When the flashing has been reinstalled, coat the seams with vinyl rubber caulk.