Stairs.

Stairs are made in stone, concrete, ferroconcrete, brick, iron, and timber; all but the latter two have been already treated. Buildings should be designed for and provided with convenient staircases, and the planning of the stairs considered as of primary, and of secondary importance. Timber stairs or steps consist of a number of wooden blocks or casings fitted into, or resting upon inclined beams called strings and carriages, which distribute the load upon the main members of adjacent floors. A rectangular landing extending across the widths of two flights and against one edge, of which both flights abut, and on which a half turn is made. An imaginary line parallel to the strings and tangential to the nosings. Vertical members between the handrail and strings to stiffen the handrail and prevent persons falling through. Wooden steps are usually built up of a number of comparatively thin casings, dressed only on the seen faces.