9.11. Eave Snow Flashing

Description: In areas where snow remains on the roof for extended periods, the snow over heated spaces thaws first. When the run-off reaches the exposed eave overhang, it freezes and forms an ice dam. As this ice dam collects more melting snow, the water backs up under the roofing material causing a leak.

Eave snow flashing is designed to prevent roof leaks under these conditions. It does this by providing a waterproof layer around the perimeter of the roof. The flashing extends at least 18" beyond the face of the exterior wall, and is lapped by the roofing a minimum of 6".

The flashing described in the details is formed with 1/2" steps running horizontally, spaced no more than 8" apart, for rigidity. Standing seam roofing is also suitable.

The minimum weight of copper used for eave snow flashing is 16 oz.

9.11A. Gable Detail

Vertical steps, 1/2" high, are formed and installed approximately 8" apart. These steps provide sheet rigidity as well as creating the horizontal lines simulating the shingle butt line. This detail shows that the 1/2" steps are malleted down within 2" of the gable end. The flashing is hooked over a continuous edge strip into a loose lock, 3/4" wide.

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9.11B. Typical Sections

These sections show that the upper edge of the flashing is folded over and cleated at 12" O.C. A cant strip is used to elevate slate or wood shingles at the edge. The eave detail shows how the flashing is hooked over the continuous edge strip to form a drip.

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9.11C. Valley Detail

At the valley, the valley sheet is installed first. The flashing is cut to lap 1-1/2" over the valley sheet. After the 1/2" steps are flattened, the valley and flashing sheets are joined together by a lapped, riveted and soldered seam.

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9.11D. Sections

The alternate cant detail shows a different copper shape that can be used for elevating slate and wood shingles. The expansion joint uses a clevis seam filled with sealant to make it waterproof.

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DWG iconDownload CAD File technical detail

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