Fixing Leaky Valleys

Q: How can I stop the roof valley leaks in my 1960s bungalow? This has always been a problem, despite having the roof reshingled and repaired in the past. The leaks don’t happen all the time, usually just during heavy rains.

A: Valleys are a weak spot in many roofs, and I suppose that offers some small consolation. The best once-and-for-all solution to the plague of leaky valleys that I’ve seen involves a system of shingling called a “closed, woven valley”. Installed over metal flashing or a flexible sheet material generically known as ice and water shield, closed valleys will perform every bit as reliably as the rest of the roof. Trouble is, few roofers like to do this work because it’s not traditional in most parts of the country. That means it might take a bit longer to get the job done. Short of having your roof stripped and reshingled with closed, woven valleys, there is a stopgap approach you can consider. Valleys like yours that leak most during hard rains usually have defective sealing where the shingles meet the open valley flashing. Sealing these areas with polyurethane caulking is the best option I know of for repair. It lasts longer than roofing tar and is available in several colours, one of which might match your roof. Sometimes it's also possible to retrofit a roof from an open to a closed valley, depending on design and age.