Valleys that have been coated with roof cement are a sure sign of previous water entry problems. Roof cement, however, is only a temporary solution to those past problems.

Copper valleys tend to develop wear holes after 40 - 60 years of service, however, many slates last in excess of 150 years. Notice how the hole forms at the edge of the slate. Roof cement patches do not work because the holes often form under the slate.

Two courses of slate on either side must be removed in order for the valley to be properly replaced.

A freshly completed valley replacement project on a historic, good quality slate roof.