Is It OK to Put Flashing on Top of the Shingles on a Roof?

Flashing Material

• Flashing is commonly delivered in rolls of flat metal. Copper, galvanized and stainless steel, and aluminum flashing are all available. Thicknesses vary but are commonly at least 0.05 inches thick. The width of rolls varies depending on the application of the flashing. Some flashing material is painted to match the shingles, and all are treated to prevent corrosion.

Placing Flashings

• Seams between two segments of the roof, which involves bending the flashing in some situations, can be covered by flashing. For example, a flashing between the exterior wall and roof would be bent at a right angle with one leg extending up the wall and the other across the roof sheathing. Use the same configuration around a chimney or vent. The flashing is held in place with galvanized roofing nails.

Sealing Flashing

• Apply roofing tar along the edge of the flashing and over the top of the nails used to hold the flashing in place, and place the shingles over the flashing. Do not drive nails through the shingles and flashing; instead fasten the shingles to the flashing using roofing tar. Seal the edges of the shingles over the flashing.

Multiple Pieces of Flashing

• Some larger roof projects require multiple pieces of flashing on the same segment. Start at the bottom of the roof with the flashing, and add the additional pieces as you work your way up the roof. Overlap the top piece of flashing over the lower pieces of flashing, and seal all the edges with roofing tar.