Previous roofers have tried to repair a large tear in the lead on the valley using a thin coat of hot bitumen tar. Being very brittle in it’s nature this has cracked with the tear as the lead has continued to sag due to excess moisture on the board underneath. Broken slates have made things worse. we have replaced the damaged slates & re-fixed any that were loose or had slipped. Then, after fully drying out the valley, we applied a solvent based glass fibre reinforced acrylic membrane in conjunction with glass fibre chopped strand mat to give the repair lasting strength.