Flat roofs, with an incline of about ½ inch to the foot, should be
covered with the flat-seam roof. The standing seam may be used on roofs
with a pitch not less than 2 inches to the foot. The tin is laid upon
the sheathing-boards without an intermediate layer of building-paper;
in fact, tar paper should never be used. In cities building codes often
require that tin roofs should be laid upon roofing felt ¹/₁₆ inch
thick, placed over the sheathing-boards, but this is a fire precaution
against burning brands which may drop upon the roof, for this felt
cushion gives an air insulation, preventing the quick ignition of the
decking below the tin.
[Illustration: Tin Roofs]
In laying the flat-seam roof a number of sheets are fastened together
to form a long strip of tin. The edges are bent over ½ inch, so that
they can be interlocked with the next strip. The tin is fastened to the
roof with tin cleats that lock into the seams of the sheets and are
fastened at the other end with two 1-inch barbed-wire nails. These
cleats are spaced about 8 inches apart. All the seams are flattened
down, and solder well sweated into them, rosin being the only flux used.
Tin, approximately in thickness 30-gauge, U. S. Standard, is called IC,
and recommended for the roof proper, while valleys and gutters should
be lined with IX tin, approximately 27-gauge. It should be painted on
both sides, before laying, with pure linseed-oil and red lead, or red
oxide, Venetian red, or metallic brown. Two coats should be given to
the exposed side and a third coat about a year later. Before the second
coat is applied the first should have dried for at least two weeks.
The construction of the standing seam roof is shown in the drawings
to consist of long strips of tin, made of standard sheets fastened
together with the flat and soldered seam, but the edges of the strips
fastened to the next strip with the so-called standing seam, which must
run parallel to the pitch of the roof. Cleats, spaced a foot apart, are
used to fasten the tin to the sheathing-boards. One edge of the next
strip is turned up 1½ inches, and then over the top of the edge of the
other strip. The cleat is locked in between the two. The upstanding
seam is then turned down again upon itself, tightly locking the strips
together.
_Copper and Zinc Roofs_
For a while, during the high prices created by the war, the thought
of building a copper roof or a zinc roof on the small house would have
been received with a doubtful shake of the head. This is no longer the
case, however, for the prices of these materials have come down to
within reason, and there is no doubt as to their durability. No one has
questioned the weathering qualities of copper or zinc. The copper roofs
which have shown such practical durability on large buildings have
usually been laid about the same as that described for standing seam
tin roofs. Cold-rolled or soft copper sheets, usually 20 inches wide,
are used for this roof covering, weighing not less than 16 ounces to
the square foot.
This type of roof is rather expensive for the small house, even with
the reduced cost of copper, and for this reason a lighter grade has
been made, and offered for use in the form of pressed-metal shingles of
very flat design. These copper shingles have been treated so that other
colors than the copper shades can be secured.
The zinc manufacturers have also placed on the market zinc shingles of
special interlocking flat design for use on small houses.
It has always been a debated question as to whether pressed-metal
shingles were architecturally permissible. Certainly there are
some forms which imitate the clay tile shingle that are decidedly
inartistic, but the more natural flat patterns are less subject to this
criticism.