Figure 6-43-A typical building paper and felt on five-ply built-up roof.
three standard lengths: 16, 18, and 24 in. The
16-in. length is perhaps the most popular. Wood
shakes are applied in much the same manner as
wood shingles.
On flat roofs, the roof covering is usually built
up. BUILT-UP ROOFING consists of several
layers (plies) of felt, set in a hot binder of melted
pitch or asphalt. Built-up roofs are always
designated by the number of plies they contain.
A five-ply built-up roof is shown in figure 6-43,
Notice that aggregate surfacing materials,
such as gravel, slag, marble, and other suitable
materials,
are used in built-up roofing to
provide a good weathering surface and protect
the bitumens from sunlight and external heat.
Exterior Trim
Before the installation of the roof sheathing
is completed, the exterior finish at and just below
the eaves of the roof, called CORNICE, can be
constructed. The practical purpose of a cornice
is to seal the joint between wall and roof
against weather penetration. Purely ornamental
parts of a cornice are called trim. Figure 6-44
shows a simple type of cornice, used on a roof
with no rafter overhang. A roof with a rafter
overhang may have the “open” cornice shown in
Figure 6-44.-Simple cornice.
6-29
