The joists are covered with a waterproof material such as asphalt, lead, zinc or copper, the three last materials being usually laid upon boarding, which stiffens the structure and forms a good surface to fix the weatherproof covering upon.
" Lean-to," " shed," or " pent " roofs are practically developments of the flat roof, one end of the joists (which are now called " rafters ") being tipped up to form a decided slope, which enables slates, tiles, corrugated iron and other materials to be employed which cannot be used upon a " flat " roof.
Among the ancients it was in request for poles, rafters, joists, and for the construction of winepresses, tables and musical instruments; and on that account was so valuable that a plantation of cypresses was considered a sufficient dowry for a daughter.
The larger trees are sawn up into planks and battens, much used for the purposes of the builder, especially for flooring, joists and rafters.
First, he made a number of leathern tubes the ends of which he contrived to fix among the joists and flooring of a fine upper-room in which Zeno entertained his friends, and then subjected it to a miniature earthquake by sending steam through the tubes.