Four Steps to Flash a Dormer
This leak-free approach begins with an impenetrable corner detail.
Synopsis: While the gold standard for roof flashing is soldered copper, the fact is that for economic reasons, the vast majority of roof flashing is done with aluminum. In this article, veteran remodeler Mike Guertin shows how to flash a dormer with bombproof details.
Photo: Mike Guertin
Roof flashing is critical to keeping a house dry, but people often get it wrong. Most roof leaks I’ve investigated are due to either undersize or improperly installed flashing. To keep out water, flashing has to be fabricated from durable materials, sized to keep out wind-driven rain, and installed in a weather-lapped fashion—that is, with the upper layers overlaying the lower layers. Also, it doesn’t hurt to design flashing to be visually appealing.
Because their front and side walls meet the roof in different ways, dormers require several techniques to integrate the flashing with the roofing material as well as…