How to Repair Valleys on a Roof

Use a broom to brush away debris such as fallen leaves, needles, seeds or branches at least twice a year. This not only helps prevent damage caused as these items break down or sprout, it allows you to check for any damage or needed repairs beneath the debris.

Wait for a week when dry weather is expected, and wait to begin working until the roof has dried from any morning dew. Inspect the valleys, looking for gaps, shrinkage of the materials, cracked shingles and other spots that may potentially leak.

Use a putty knife to apply sealant or roof pitch to any holes or cracks. Replace any damaged or missing individual shingles. Apply roofing tar along the edge of a shingle-to-flashing joint in a continuous bead, sealing the edges of the valley.

Apply roofing cement beneath the shingles to secure them, if necessary. To prevent leaks, do not use nails to secure shingles within 6 inches of the valley seam. The shingles around the valleys are purposefully not nailed down in order to prevent "shingle strain." Usually only high winds or extremely heavy rain will cause a problem with these shingles; but in some cases, shingle movement can loosen the flashing nails. Avoid trying to nail the flashing down further, even if it is being loosened by wind or appears to have been left unattached.

Weave new shingles beneath the existing shingles to create a simulation of a closed valley system if necessary. Also, consider switching to closed valleys if you replace your roof. Replace the flashing if you must replace a portion of the roofing.