Dormer Roof Lead Flashing

Damaged or improperly installed roof flashing especially around the chimney or dormer is one of the most common causes of roof leaks.

Dormer roof lead flashing.

Shed dormers require a continuous strip of flashing along the top of the lower roof plane where it meets the steeper roof plane. Ideally this custom flashing will have soldered corners but if not carefully notch the metal at the dormer corners and wrap the vertical leg around the corner onto the side wall. Use taller pieces of step flashing towards the top so the pieces can be bent over the dormer roof to help keep out snow and wind blown rain. Proper installation of flashing and counter flashing at the intersection of a vertical wall with a roof surface is required to avoid roof leaks.

Dormer to roof junction this detail illustrates the first method described above using individual copper flashing squares woven between the shingles tile or slate. 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 with the house s water resistive barrier wrb of housewrap or felt paper. Also they require sidewall flashings. The joint between the copper apron and base flashing is soldered.

The flashing extends at least 4 onto the roof and 8 up the wall. According to the federal emergency management agency fema improper roof flashing could lead to wood rot and even deck collapse. Lay a bead of roofing cement along the shingles just below the dormer and bed the metal base flashing into it. A critical juncture that often fails is where these two flashings meet.