Builtup Roofs

Built-up roof coverings are installed by roofing firms that specialize in this work. Roofs of this type may have three or more layers of roofing felt. Each layer is mopped down with tar or asphalt, the final surface being coated with the same material. The surface is then covered with gravel (embedded in the asphalt or tar) or with a cap sheet. This covering provides ballast and protection from the sun's ultraviolet radiation. It is important to note that coal tar products and asphalt products are not compatible and must not be used together.

The eave line of projecting roofs is usually finished with metal edging or flashing. A gravel stop or cant strip is used in conjunction with the flashing at the eaves when the roof is covered with gravel (Fig. 76A). Where built-up roofing is finished against another wall (except a masonry-clad wall), the roofing is mopped to the cant strip and turned up the wall at least 6 in. (150 mm). The wall sheathing paper and siding is then applied over the roof membrane. (Fig. 76B).

Built-up roof: (A) eave flashing and drip; (B) junction of built-up roof and wall covered with siding.

o siding sheathing membrane 2" (50 mm) minimum lap membrane flashing cant strip roof sheathing built-up roofing metal gravel stop fascia board

Built-up roof: (A) eave flashing and drip; (B) junction of built-up roof and wall covered with siding.

siding fascia board

Where a built-up roof intersects a masonry-clad wall, the roof membrane is similarly returned up the face of the masonry. Counter-flashing is then added. This counter-flashing should be embedded into the mortar joints at least i in. (25 mm), extending down the wall about 6 in. (150 mm) and lapping over the flashing at least 4 in. (100 mm).

Single-ply membranes can also be used for flat roofs. They consist of

Details of sheet metal roofing.

nailing strips for sheet metal roofing

Details of sheet metal roofing.

nailing strips for sheet metal roofing eave starter

end wall flashing

Dk eave starter end wall flashing

side wall flashing

various synthetic materials that are resistant to freeze-thaw cycling, ozone attack and ultraviolet degradation. They are relatively simple to lay, but are not often used on the small roofs that are typically part of wood-frame construction.

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