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5thWall Building Diagnostics Consultants Government Services Annex <br /> District Attorney Office <br /> Roof Replacement <br /> November 2009 <br /> D . Verify installation of all appropriate baseflashings prior to installation of sheet metal . <br /> 3 . 02 Installation-General <br /> A . Dissimilar metals shall be kept separated to prevent galvanic action . Preventive measures <br /> shall include separation by suitable bituminous paint . <br /> B . Where bituminous materials are to be applied to sheet metal , the flanges shall first be <br /> primed with an asphaltic primer . The primer shall be interrupted where caulking is to be <br /> applied . <br /> co All metal flanges shall be installed on top of membrane and set in a full bed of sealant . <br /> D . Flanges of edge metal shall terminate 1 /2 inch from roof-side edge of nailer . <br /> E . All exposed edges of sheet metal shall be folded back, or " hemmed " , on concealed <br /> surfaces . <br /> F . Finish all sheet metal watertight and weathertight . <br /> G . Where lap seams do not have a j oint cover, lap according to pitch, but in no case less than <br /> three inches . Make all lap seams in the direction of water flow . <br /> 3 . 04 Edge Metal and Trim <br /> A . Provide and install edge metal and trim at all gables , rakes , and eaves . Fabricate edge <br /> metal and trim from copper metal . <br /> Be Secure metal to substrate with fasteners at 12 inches o . c . Set flanges of metal in a full <br /> bed of flashing cement prior to securing with fasteners . <br /> C . Place eave and rake metal tight with fascia board . Lap joints 2 inches and seal with <br /> flashing cement . <br /> 3 . 05 Step Flashing <br /> A . Provide and install step flashing at vertical walls and interfaces with shingle roof systems . <br /> Be Step flashing shall be L - shaped with horizontal leg 5 inches in lengths vertical leg shall <br /> be of sufficient length to extend under counterflashing a minimum of 4 inches at the <br /> upslope side of the step flashing . Width of step flashing shall match that of the shingle . <br /> C . Install step flashing in conjunction with shingle installation . <br /> 3 . 06 Counterflashing <br /> A . Install counterflashing at chimneys , walls , and other vertical surfaces intersecting or <br /> abutting shingle roof areas . <br /> Be Fabricate counterflashing with vertical face dimension of five inches unless otherwise <br /> shown . Provide a stiffening break approximately one third of the vertical dimension from <br /> the top of the counterflashing . Provide 5 / 8 inch hem at bottom of vertical face . <br /> 09 -26 Sheet Metal Flashing and Trim <br /> 076200 - 5 <br />