Previous to the granting of a patent to John Walter, in 1882, there were
no tin shingles manufactured for the trade in the United States, with the
exception of those which covered more than two-thirds of their surface
to get one-third exposed to the weather; the same is commonly done with
wood shingles. This made them too expensive for general use. The Walter’s
patent made it practical to expose five-sixths of the surface and only
conceal one-sixth of the shingle. This great saving at once reduced the
cost of metal shingles over one-half, and enabled the National Sheet
Metal Roofing Co., which controls this patent, to put on the market the
best metal roofing in the world, at prices that compete with ordinary
wood shingles. (See “Comparative Cost,” pages 26 and 27.)
How this was done is best expressed in the claim granted the patentee,
copied from the United States Official Gazette:
“A metal roofing plate having a gutter formed by corrugations
at one side, and a perforated flange at the side of the gutter,
whereby it shall be nailed to the roof of a house; a broad
corrugation at the other side adapted to form a seam with the
adjoining edge of a corresponding plate, substantially as shown
and described.”
[Illustration]
The advantage of this lock is that it makes a water-tight seam without
soldering or hammering down. The plates are joined as easy as crossing
two sticks, with ample provision for expansion and contraction. This lock
is the perfection of simplicity; there is no exposed seam where water is
liable to lodge and cause rust; no cleats are used, and no tin springs
are necessary to hold the side edges of connecting plates to prevent
water seeping through.