This section is from the book "A Treatise On Architecture And Building Construction Vol3: Stair Building, Ornamental Ironwork, Roofing, Sheet-Metal Work, Electric-Light Wiring And Bellwork", by The Colliery Engineer Co.. Also available from Amazon: A Treatise On Architecture And Building Construction.
Where the stairways of a building are of considerable length, and are straight in plan, it is best to break the flight by a platform. Such a platform may be projected from the side wall, as shown in Fig. 12. In a brick wall, the lookouts a, a should be set in at least 8 inches with slip keys tightly wedged between the bricks and the top of the timbers. The braces b, b should be well fitted and spiked to the lookouts; these braces serve to keep the platform square and enable it to resist distortion by stress brought to bear on the carriage timbers c, and should be made of thoroughly seasoned wood. A flight terminating in a platform should not contain more than 12 steps. A perspective sketch of the platform is shown in Fig. 13.