Verwandte Artikel zu Elementary building construction and drawing
Inhaltsangabe
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1891 edition. Excerpt: ...by increasing their weight. The following sizes of slates are in common use:--There are two methods of nailing slates--viz. (1) near the head, (2) near the centre. The respective advantages of these systems will be described presently. When slate boarding is used, it is often covered with asphalted felt before the slates are laid. This material keeps the roof timbers dry when leakage occurs through defects in the slating. It is, besides, an excellent non-conductor of heat. For the sake of appearance and soundness, the slates to be used for a roof should be sorted into three divisions according to their thickness, which varies. The thickest must be laid at the bottom of the roof slope, and the thinnest at the top near the ridge. The following terms are applied to the different parts of a slate:--. (1) Bed.,-the under surface. (2) Back... the upper surface. (3) Tail... the lower edge. (4) Head.. the upper edge. (5) Margin.. the portion of each slate exposed to view on the outside of the roof. Slates may be secured to roof boarding or battens. In every case two nails should be used to fasten each slate. These are preferably of copper, and about inch long. Zinc and iron are sometimes used; when of the latter material, the nails should be well galvanized or dipped in boiled oil to prevent corrosion. 100. Lap.--This term is applied, in the case of slates nailed at the head, to the distance which the tail of one course of slates overlaps the nail holes of the course next but one below it. Thus in fig. 191, which illustrates the arrangement of slates 16 inches long and 8 inches broad (ladies), the lap is given at 3 inches. In fig. 190 the slates (countesses) are large, being 20 inches long and 10 inches wide. These are preferably nailed near the...
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