Stairs in houses are generally of wood, framed together, but occasionally solid steps of oak are used after the manner of stone steps. Solid wood steps are more durable and offer greater resistance to fire than do the ordinary framed wood steps. Stone steps are cold to the touch, and apt to snap or disintegrate under the action of fire. The same remarks apply to concrete steps, although the fire-resistance of these may be improved by using a suitable aggregate, and by bedding in the concrete a meshwork of iron or steel in the form of rods, bars, expanded metal, etc. The height of the riser should be proportioned to the breadth of the tread, the following being a good rule: - Breadth of tread + twice the height of riser = 2 feet. It Is not customary, however, to have risers less thau five inches or more than nine inches. Turnstepe or winders are a source of danger; so also are odd steps in unexpected places. Dark staircases are very objectionable.