In the construction of wooden stairs two distinct methods are employed, the advocates of each claiming that theirs is the best. Each method naturally possesses some advantage over the other, and while in most cases either method will give satisfactory results, there are often particular conditions under which one or the other is better adapted.
As there are no well-recognized terms for designating the different methods, it is necessary to describe in the specifications the particular manner in which the stairs are to be built.
By the first method, which might be designated as the Boston method, as it is the principal method used in that vicinity, the carriages and other supports for the finished stairs are put up by the stair-builder before the building is lathed, temporary treads being nailed to the carriages for the convenience of the workmen. The carriages are accurately cut from pine or spruce planks to fit the treads and risers and made to line perfectly true, level and square. As they carry the weight of the stairs and the loads which come upon them they should be securely fastened in place and the timber on which the bottom of the carriages rest should be of sufficient strength to carry the entire weight of the flight above it. For first-class work the carriages should be spaced 12 inches on centres, and in long flights a false riser should be spiked to the rise of the carriages every four or five steps, as shown in Fig. 308, the step being cut back to allow for the thickness of the board.
When a straight flight of stairs, with a platform, like that shown in Fig. 296, is to be built it is desirable to extend the platform posts to the floor timbers below, but if this cannot conveniently be done, and there is no partition under the outer carriage, the carriages may be supported or strengthened at the platform by pieces of flat iron, screwed or bolted to each carriage, as shown in Fig. 297. Stairs for public buildings, factories, etc., however, should invariably have the platform posts carried down to a solid support.
After the plastering is dry, and while the other interior finish is being put up, the stair-builder puts in place the finished portions of the stairs one piece at a time. The treads and risers are all " got out " at the shop, the under sides of the treads being grooved to receive fig. 299. - Open String.
a tongue worked on the upper edge of the riser and the bottom of the riser grooved to receive a tongue on the back edge of the tread, as shown in Fig. 298. The risers are first nailed to the carriages, commencing at the top, and then the treads are fitted into them and nailed. The wall string or base is roughly scribed to the profile of the stairs and the edge cut away at the back to form a tongue, which is then driven into a groove cut in the ends of the treads and risers, as shown in the figure, the nosing being cut off so as to butt against the base. This permits of shrinkage in the base, without leaving an open joint at the intersection. Considerable care has to be exercised in cutting the groove for the base to get it at exactly the right distance from the wall line.
Fig. 300.- Closed or Curb.
Second on line
The outer face of the stair may be finished either as shown in Fig. 299 or as in Fig. 300. The former is called an open string and the latter a closed or curb string; the open string in this method of construction being the cheaper.
In " open string " stairs a plain board, cut to the profile of the stairs and mitred against the ends of the risers, is first nailed to the carriage or blocked out from it so as to cover the plaster, and the nosing is continued across the end of the tread by means of a solid moulding worked to the shape of the nosing and mitring with it, as shown by the detail drawing, Fig. 303, the other end of the moulding being returned on itself. Before this moulding is fastened in place the balusters are dovetailed into the ends of the treads as shown at F. If the stairs are to be finished with a " closed string " the string in this method of construction is made hollow, as shown by the section
Fig. 301, the inner part being tongued into the treads and risers in the same way as the wall string. The outer string is then put up, being generally nailed to furring blocks, and the top member being next fastened in place to complete the string; the balusters being either mortised into it or simply cut on a bevel and nailed. As the string must be quite wide it is generally paneled to prevent excessive shrinking. Fig. 302 shows another method of capping a curb string, which the author prefers to that shown in Fig. 301. The piece B is cut between the balusters and holds them in place.
Open string stairs are often ornamented by planting thin brackets of wood on the face of the string before the nosing is put on, as in Cand D, Fig. 299. They should be mitred with the end of the riser. In very ornamental work these brackets are usually carved, as shown in Fig. 304.
Stairs are sometimes finished as in Fig. 305, the back and under side of the steps being paneled to appear like solid steps.
The newel and angle posts, which are generally built up out of thin stuff, are put up before the string and the latter is housed into them.
Stair-builders will sometimes try to convince the architect that to secure a strong stair it is necessary to build in the angle posts when the carriages are put up, but if the stair-builder thoroughly understands his work the framework can be as solidly constructed without the posts, which may then be put up with the other finish work and thus escape being subjected to the dampness invariably produced by the wet plastering. In inferior pine stairs the posts may be built in with the carriages and boxed to prevent being injured. 187. In the second method of construction, which may be called the English method*, the finished portion of the stairs is all put together at the shop and carried bodily to the building and set in place on the carriages, which are often made as in Fig. 306. When built in this way the treads and risers are generally tongued together as before described, except that sometimes
• The author is informed that this method is used almost exclusively in California, and 10 a the moulding under the nosing is also ploughed into the tread, and all glued together.
The connection of the treads and risers with the base (called in this construction the " wall string "), however, is made in an entirely different manner; the profile of the stair, including the nosing, is carefully traced on the string, which is then cut out as at A, Fig. 307, so that the ends of the treads and risers may be "housed" into it at least ½ inch, and then wedged and glued, as shown at B.
The treads and risers should also be blocked and glued together, as shown in Fig. 306.
The outer string is then put on and glued, and if a curb or close string the treads and risers are housed into it, as with the wall string, a single string 1 ¾ inches thick often being used in that case.
When this method of construction is used the base or wall string should be at least 1 1/3 inches thick, and it is better to have a curb string on the outside, the inside face being worked in the same way as the wall string. For the inferior stairs in dwellings this makes the cheapest construction, and if well housed, blocked and glued, they will have sufficient strength without carriages, when not over 3 feet wide, and the string on each side is solidly nailed to a partition. It is customary in such stairs, however, to put up 2x4 joist under the stairs to help support them and also to receive the lathing underneath.
When the stairs are put together in the shop the only way in which they can be accurately fitted to the carriages is by wedges driven from below, and this obviously can not be done after the soffit or under side of the stairs is plastered, so that the plastering, if there is any, must be done after the stairs are finished.
This is a very serious objection to the English method of construction, as no plastering should ever be done in a building after the finished work is in place, especially if the wood is to be varnished. If the stairs are put up without wedging they are pretty sure to squeak.
The author, therefore, in his own practice always specifies the Boston method of construction for all but inferior pine staircases, unless the stairs are to be paneled underneath, in which case a better job can usually be obtained by the English method of construction. Where plastering is necessary after the woodwork is completed, some kind of plaster board should be used for the ground, and then only a thin white coat will be required to finish it.
The treads in stairs for public buildings, if of wood, should be of oak (Georgia pine or Oregon pine will answer very well) and never less than 1 1/8 inches thick, and 1 ¾-inch treads are often used.
When more than 1 1/8 inches thick, however, it is a good idea to groove them on the bottom, as at A, Fig. 309, so that they will not warp.
There is still another method of stair building much used in Pennsylvania, which is a combination of the two methods above described. In this
■ method the carriages or horses are cut to fit the steps, as shown in Fig. 308, and put up to line perfectly. To the wall, a 3x4 or 3x6 joist, called the "wall bearer," is nailed or spiked, so that the top will be about ¾ inch below the back edge of the risers.
In long flights a false riser is nailed to every fifth or sixth riser of the carriages (the treads being cut short for the purpose) and fastened securely to the wall, the inner end being thrown a little higher than level. This braces and stiffens the work very much. After the plastering is dry the wall string is set and nailed to the wall, having been previously housed out for the steps as in the English method.
The risers and treads are then driven into the wall string, commencing at the bottom, and nailed to the carriages
Wedges are also driven in and glued on top of the wall bearer to give additional support to the back edge of the steps, as shown in Fig. 309.
The inside of face string (if a curb string) is then tongued into a groove cut in the treads and risers, as in the Boston method. This method differs from the Boston method only in the wall bearer and string and in having the wedges on top of the wall bearer, and in this respect is probably superior to the first method described.
For the finest grades of work the material should all be painted on the back and filled and shellaced on the face before taking to the building, which should be thoroughly dried out beforehand.