lbs. per square foot.

Aprons and Flashings

5

Thicker if much exposed.

Roofs

6 to 8

Flats

Gutters

Hips and Ridges

6 or 7

Lead Pipes of very large diameter may be made out of sheet lead, but smaller ones should be drawn.

Zinc is obtained from ores of the metal. It is easily fusible, malleable when pure, soon destroyed by air containing acid.

It is used by the builder for roof coverings, gutters, cisterns, chimney pots, slate nails, ornaments, and for covering iron (galvanising) to keep it from rusting.

Good sheet zinc is of uniform colour, tough, easily bent backwards and forwards without cracking. The gauges used for roofs are mentioned at p. 62.

Tin is used for lining lead pipes and for small gas tubing. It is very soft, weak, and malleable, and more easily fusible than any other metal.