This section is from the book "A Treatise On Architecture And Building Construction Vol2: Masonry. Carpentry. Joinery", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
Dados And Wainscots. In some rooms where there is likelihood of much changing of the position of the furniture, such as the dining room, kitchen, library, etc., as well as in the bath room, halls, staircase walls, etc., it is sometimes desirable to affix a broad band or molding against the wall, about 3 feet from the floor and parallel to the skirting, to prevent the backs of the chairs from marring the plaster, and at the same time to form a cap to the dado or wainscot if such is desirable. This chair rail is affixed to a narrow ground, and should, of course, cover the joint between the ground and the plaster. The interval between the chair rail and the skirting is called the dado, or wainscot. It may be paneled in wood, covered with narrow lining, or simply left plain in plaster.
27. In a paneled wainscot, such as is shown in Fig. 15, great care is necessary in fitting all the joints, and due consideration must be given to the subject of shrinkage, so that the subsequent drying out of the material will not cause unsightly cracks or open joints. The vertical pieces a, and the horizontal members b, b\ and b", dividing the surface of the wainscot into panels, called stiles and rails, respectively, are framed and glued together. The panels c are left free to shrink or swell to a greater or less extent, without disturbing the surrounding members. The end stiles a' extend from the floor to the top of the top rail b, and are mortised to receive the tenons of the rails b, b', b", as shown at e, e', and e". The rails are also mortised, and receive the tenons of the short stiles, or muntins a, a", as shown at f.
In the edge of each stile and rail a groove is worked to the depth of the molding g, and the edges of the panels c are beveled off or hollowed out and inserted in this groove, as shown at h. The moldings g when small may be worked on the edges of the stiles and rails, but when large and heavy they must be worked from separate stock and fitted in position afterwards.
The panels are thus practically separate from the surrounding frame, and are free to shrink without danger of splitting. At the same time, since the amount of cross-grain in the extent of the wainscot is equal only to the sum of all widths of the stiles in one direction and to all the widths of the rails in the other direction, the shrinkable material is reduced to a minimum, so that the wainscot, when constructed with well seasoned material, will give good results.
28. Where the face of the wainscot is to be a plain impaneled surface of wood, still further precautions must be taken to guard against the effects of shrinkage. Two general methods are recognized as satisfactory for the purpose of securing these large surfaces of work against the effects of warping and shrinking. One is to make the wainscot of narrow boards, not more than three times their thickness in width, and with the grain reversed in every second piece - that is, to have the heart side of the material show on each side at every second board. After being tongued-and-grooved and glued together, the boards are secured against warping by means of keys inserted as described in Art. 18.
Another method is to build the wainscot with several thicknesses of thin stock, reversing the grain in each piece. This method is the better one for long, unbroken surfaces, as its shrinkage is prevented almost entirely; but, when the design of the wainscot will permit the building of a stile or pilaster every 6 or 8 feet, the narrow, keyed boards will be found to serve very satisfactorily, if a 1/2-inch space between the ends under the pilasters is left to provide room for expansion and contraction. These keyed sections, if the grain runs vertically, should be secured to the wall only in the center of their lengths, and left loose the rest of the way to come and go with atmospheric changes. If the grain runs lengthwise of the wainscot, no stiles or pilasters will be required to cover the joints, as the wainscot can be built up of one continuous piece; but the shrinkage must be provided for between the base and the coping, or surbase, and the wainscot secured only in the center of its height, so as to allow the top and bottom to come and go.
29. After the paneling of the wainscot is completed, it is secured to the grounds, shown at j, Fig. 15, which were set in place to receive it, before the plastering was applied. Every possible precaution must be taken to insure the drying of the plaster, as the presence of the slightest moisture is fatal to permanent joiners' work. Under the most favorable conditions, there should be allowed at least a week to dry each of the first two coats of plaster, and the hardwood trim should not be applied for two weeks after the finished coat is spread. In damp or rainy weather much more time should be allowed. The patent prepared plasters and wall cements take less time than this to dry, and a deduction can be made when these are used, according to the rapidity of their drying, as described in Masonry.
30. When the wainscot is secured horizontally through its center, and allowed to shrink at the top and bottom, a horizontal ground must be provided to nail it to, and additional grounds must be provided at top and bottom to secure the coping and the base, as well as to form a backing for the upper and lower edges of the dado.
When the wainscot is secured along vertical lines every 8 or 10 feet of its length, vertical grounds must be provided, in addition to the grounds at top and bottom, as above described.
31. In laying out and spacing the stiles, rails, and panels of a wainscot, it is first necessary to prepare a long measuring rod, about 2 inches wide, through the center of which a line is drawn, as shown at a b in Fig. 16. The rod is then divided into a number of spaces, corresponding with the widths of the stiles and panels on one side of the line, and with the width of the rails and length of the panels on the other side. That is, the divisions in Fig. 16 which are above the line a b, ascd, lm, l' m', etc., show the location and widths of the stiles a in Fig. 15, while the large divisions, as dl, ml', etc., show the width of the panels c.
The divisions ef, gh, and ik below the line ab mark the widths of the rails b, b', and b" in Fig. 15, and the spaces fg and h i show the width and length of the panels.
The three rails b, b', b" are clamped together with hand screws, and the rod is then used to lay out the width of, and spacing between, the stiles; these divisions are then squared across the three rails with a square, and marked with a scratch awl or the point of a knife. The stiles are then marked in the same way, three or four at a time, and an allowance is made for the length of the tenons on the ends. In laying out the measuring rods for the spacing of the stiles and panels, it must be remembered that a stile must exist on each end of the wainscot; and to determine the number of panels required, the width of one stile and twice the thickness of the wainscot must be subtracted from the length of the room, if the wainscot returns on two interior angles, and the remainder is divided by the sum of the widths of one panel and one stile. If, however, the wainscot returns around one exterior and one interior angle, as at A and B in Fig. 15, the width of one stile only should be deducted.
32. In Fig. 15, the length of the wall along which the wainscot is built is 3 feet 11 inches and the panels are each 4 1/2 inches wide; the stiles are all 3 inches wide, except the end one A, which is 3 1/2- inches wide. If we now subtract 3 1/2 inches, the width of the end stile, from 3 feet 11 inches, the length of the wall, we have 3 feet 7 1/2 inches of wainscot to be divided into six equal panels and six equal stiles. The combined width of a panel and stile is, therefore, 43 1/2| in. ÷ 6 = 7 1/4 inches. Since the stiles are to be 3 inches wide, then 7 1/4 - 3 = 4 1/4 inches is the width of each panel opening. If the wall at A had returned on an interior angle, like the wall at B, we would have the end stile at A of the same width as the stile at B, and we would then have deducted 3 inches, the width of one stile, + 2 1/4 inches, twice the thickness of the wainscot, from 3 feet 11 inches, which would give us about 6 3/3 1/2 inches as the width of each panel and stile combined; and, allowing 3 inches for the stiles, each panel opening would be 3 3/3 1/2 inches in width. The panels themselves, however, will be wider than that, as a proper allowance must be made all around for their insertion in the groove, as shown at h.
33. After all the mortises and tenons are cut and fitted, and each has been marked so that it can be returned to the same place to which it was fitted, the pieces of wainscot are taken apart and laid in a pile preparatory to gluing. Only the shoulders and faces of the mortises and the shoulder ends of the tenons receive the glue, and the stiles are forced into the rails as soon after the glue is applied as possible. The lower stiles are glued in the bottom rail first, then their upper tenons are covered with glue in the same manner, and the middle rail b' is forced over them. The upper stiles are then glued into the middle rail; and finally the top rail b is glued in place, and the whole form is drawn together with bench clamps until the glue is thoroughly dry.
34. In all joiners' work, framed together with mortise and tenon, care must be taken to clean out the mortises thoroughly, and dust off the tenons before gluing; each tenon must be tried in the mortise to which it belongs and any unevenness removed, to insure its proper fit. All framed work should have its parts heated thoroughly before being clamped and glued together. If, when a piece of work is being clamped up, any rail or stile has a tendency to warp, then that rail or stile must be clamped in place with a bench screw under a piece of thick plank, and must so remain until the glue is dry. Care must always be taken that an extreme pressure of the clamps does not cause the work to deflect or wind, as it is exceedingly important in all kinds of paneled work that the whole face of the frame be kept in place, out of wind, until the glue is thoroughly set or dry.