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.
In Fig. 25 is shown the plan of the top winders of a stairway similar to that in Fig. 23, a, b, and c being the principal timbers in position. The timber a is set in place after the stringers are put up, nailed to the floorbeam at d, and fastened to the wall at e. A piece of furring strip held in the direction ed, together with a straightedge tried along the line of the risers, will indicate the best position for this timber.
The bottom of the flight, as shown in Fig. 26 (a), may be timbered by securely placing a level piece f k extending from the front stringer into the wall, and then the two timbers g h and l m at a steeper pitch than the main timbers n and o. To do this may require the insertion across the well hole of the floorbeamy j i; this is shown by the elevation at (b), where l m and g h of the plan are seen at, and lettered, g' h', and n and o at n'. Or, instead of timbering in this manner, omit the level piece k f and place a diagonal timber i k, as at the top, and continue the principal timbers n and o to meet it. The remaining timbers are filled in as required for furring, which must be done so as to allow the lath to be nailed on in the direction of the risers. In order to obtain a smooth, curved surface on the soffit - which will be more or less warped - care must be taken to aline the blocking by means of a guide lath. In lathing so placed, care must be taken that space has been allowed at all points, for the rivet of the plaster under stairways is subjected, at times, to heavy-jarring which is likely to loosen the plaster unless it is well keyed or riveted.