The Slate used for roofs is an altered form of clay, possessing a laminated structure. The ease with which it splits along the planes, renders it peculiarly suitable for this purpose. The Welsh slates are considered the best.
Terra-cotta is made from certain kinds of clay, mixed with glass, pottery or sand; then ground up, strained, and kneaded; and lastly thrown into moulds and baked in a kiln.
Iron and Wood have occasionally been employed alone in building houses. The former, owing to its good conducting powers for heat, is cold in winter and hot in summer; while the latter becomes rotten from exposure to wet, and is also very combustible. Corrugated iron buildings lined with wood are also employed, but are not very satisfactory.
For roofs, slates or tiles are the materials most frequently employed; but occasionally lead and corrugated iron are used, also thatch in country places, and tarred felt for temporary buildings.
Lead is the most suitable metallic covering for roofs, as it is durable and easily worked. It is, however, heavy and demands considerable strength in the timbers by which it is supported. Galvanized iron has also been largely used. It is cheaper and lighter than lead. Both lead and zinc require very careful laying if they are to be weather-tight.
Thatch protects the interior of a house well from extremes of heat and cold.
[CHAPTER XXXII.]
CONSTRUCTION OF THE HOUSE.
In preparing to build a house, or in entering into a house already built, the following requisites should each receive careful attention:—
1. The site of the house should be healthy, and its relation to surrounding objects in accordance with the laws of health. (See page [201]).