Use of Aluminum sheet flashing for gutters and other parts of the house

dezignhome.blogspot.com In house construction, the sheet metal work normally consists of flashing. gutter. and downspouts, and sometimes attic ventilators. Flashing  often provided to present wicking action by jonts between moisture.absorhent rnaterials. It might also be used to provide protection from wind.driven rain or from action of melting snows. For instance, damage from ice dams is often the result of inadequste flashing. Thus. proper installation of these materials is important, as well as their selection and location.

Gutters are installed at the cornice line of a pitched roof house to carry the rain or melted snow to the downspouts and away from the foundation area. They are especially needed for houses with narrow roof overhangs. Where positive rain disposal cannot he assured, downspouts should be connected with storm sewers or other drains. Poor drainage away from the wall is often the cause of wet basements and other moisture problems.

Materials
Materials most commonly used for sheet-metal work are galvanized metal, aluminum, copper, and stainless steel. Near the seacoast, where the salt in the air may corrode galvanized sheet metal, copper or stainless steel is preferred for gutters, downspouts. and flashings. Molded wood gutters, cut from solid pieces of DougIas-fir or redwood. are also used in coastal areas because they are not affected by the corrosive atmosphere. Wood gutters can be attractive in appearance and are preferred by some builders.

Galvanized (zinc coated)  sheet metal is used in two weights of zinc coatings: 1.25 and 1.50 ounces per square foot (total weight of coating on both sides). When the lightly coated 1.25ounce sheet is used for exposed flashing and for gutters and downspouts. 26- gage metal is required. With the heavier 1.50-ounce coating, a 28-gage metal is satisfactory for most metal work. except that gutters should be 26.gage.

Aluminum flashing should have a minimum thickness of 0.019 inch, the same as for roof valleys. Gutters should be made from 0.027-inch-thick metal and downspouis from 0.020-inch thickness. Copper for flashing and similar uses should have a minimum thickness of 0020 inch (16 oz.). Aluminum is not normally used when it comes in contact with concrete or stucco unless it i protected with a coat of asphal. turn or other protection against reaction with the alkali in the cement.

The types of metal fastenings, such a nails and screws. and the hangers and clips used with the various metals, are important to prevent corrosion or deterioration when unlike metals are used together. For aluminum, only aluminum or stainless steel fasteners should be usrd. For ropper flashing, use copper nails and fitting. Galvanized sheet metal or terneplate shouId be fastened with galvanized or stainless-steel fasteners.

Flashing
Flashing should be used at the junction of a roof and a wood or masonry wall, at chimneys, over exposed doors and windows, at siding rnafrrial changes, in roof valleys, and other areas where rain or melted snow may penetrate into the house.

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