additional step. The platform, however, is one riser lower, making it 6 feet 8 inches; but if the total depth of the platform can be made 6 inches, thus reducing its depth 4 inches, the height to the soffit of the platform will be 7 feet.
27. Winding Treads. — In Fig. 22Fig. 22. An enclosed stairway. is shown an enclosed stairway, illustrating the method of f laying out the wall stringer, easement curves, etc. The widths of the winding treads at the wall are projected down from the plan by lines k l, m n, etc. Then the wall stringer a b, at right angles to the main wall stringer a e, is revolved as shown, parallel to the main wall stringer and laid out in a similar manner; a’ b’ c\' d’ shows the stringer a b in elevation. The stringer e f is treated in a similar manner. The story rod is shown at the left, and the steps are projected from it and from the plan, as shown at step 4. Where the treads are wide, as in steps 1, 2, and 3, the line of the nosings makes an angle with the horizontal different from that made by the line of the nosings in the body of the stairway. This is because the uprights, or risers, remain the same, while the horizontals, or treads, vary in width.
28. Easement Curves. — At the angles, easement curves are necessary, or, at least, advisable. At h is shown a method of drawing an easement curve. From the vertex h lay off equal distances in both directions, as 1, 2, 3, 4, etc. Draw lines from 5 to 6, 4 to 7, etc. Through the points of intersection of these lines, draw a curved line by means of a spline. Otherwise, if the angle at h is sharp, perpendiculars may be drawn until they intersect, as at o; the curve can then be drawn with a compass.
29. Items of Detail. — Both wall and front stringers are to be mortised, or housed; for the steps, the treads and risers are to be glued together, wedged and back nailed, as before explained, in order to secure good, solid work. The front stringer has a vertical strip 4 inches wide spliced and glued to it so as to receive the winders. The well hole must be framed wide enough to include, beside the figured width of the stairway, the thickness of the enclosing lining.