Flashings and Copings:
Roof Penetrations

Description: Roof penetrations can be categorized by whether the roof is sloped or flat. The preferred method of flashing penetrations through flat roofs involves the construction of a curb around the opening. Small penetrations often do not require curbs.

With sloped roofs, the general approach is to attach the flashing before the roofing is installed. The shingles, slate or tile are placed over the flashing on the upper and two sides and slipped under the lower edge of the flashing. This approach is similar to the chimney flashing in Detail C. A concern with penetrations in sloped roofs is ensuring that no pockets are created where water can collect. If the shape of the flashing is such that water does not flow freely, a cricket is constructed on the high side of the flashing, similar to the one in Detail D.

The minimum weight for copper sheets used in flashing roof penetrations is 16 oz.

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A. Ventilator Flashing This detail illustrates a method of flashing a ventilator on a sloped roof. The base flashing extends onto the roof a minimum of 4" and is soldered to the ventilator. The lower edge is hemmed for stiffness. Large flashings are formed with a hook edge on the top and sides and cleated to the sheathing at 12" O.C. maximum.

Straps may be attached inside the stack section of the ventilator and to the structural framing for additional support.

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B. Long Pipe Flashing This detail is used for pipes that continue above the roof, and cannot be flashed as shown in Detail D. The copper base flashing extends a maximum of 4" onto the roof. The horizontal portion is nailed to wood blocking or to a nailable deck. It extends up at least 9", and is lapped at least 4" by the counterflashing. The cap flashing is attached to the pipe with a draw band. The cap flashing is sealed at its top edge where it meets the pipe.

C. Vent Pipe Flashing - Copper Roof The copper base flashing extends a minimum of 6" onto the roof in all directions. The upper edge is held by at least 2 cleats and is locked into the roof pans. Any batten or standing seams that are interrupted at the upper joint, are to be continued below the lower joint.

A copper sleeve is soldered to the base flashing. This sleeve runs up to the top of the vent pipe. A copper cap is placed over the exposed edges and is soldered to the sleeve.

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D. Vent Pipe Flashing Methods - Flat Roof Two methods of dealing with this condition are shown. The one on the right uses a separate copper cap flashing, the one on the left uses a single sheet of copper for the base and cap flashing.

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E. Skylight Head Flashing Detail This detail shows the head of an aluminum skylight with a wood curb installed in a standing seam copper roof. The 20 oz., minimum, copper flashing is formed into a water diverter as shown. Effective separation of the aluminum and the copper is provided with the use of butyl tape. This tape is formed into an "L" shape, and applied over the flashing on all four sides of the curb, to fully cover any copper.

The roof edge of the flashing is locked and soldered into a copper apron. The apron is cleated at its upper edge and is joined to the copper roof pans with a transverse seam. Any standing seams that are interrupted at the upper joint, are to be continued below the skylight.

The sides of the skylight are flashed similarly, except that a water diverter is not used. The edge of the copper flashing is brought over the top of the curb.

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F. Pipe Penetration with Wood Curb This detail shows a penetration with a wood curb. The composition flashing is brought up the cant strip and blocking, at least 8". Copper flashing laps over the composition flashing a minimum of 4". The top edge of the copper is held by a draw band tightened around the pipe. The exposed copper edge is then sealed.

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