All joints in carpentry should be made in such a manner that the timbers are weakened as little as possible by loss of wood; and wherever one bearing timber has to support others it is of great advantage, if possible, to nail fillets on to the sides of the timber, and notch the others over it (as figs. 274 and 275), to avoid weakening the one by the mortises to take the tenons of the other. The weaker method is shown on the right, and the preferable and stronger method on the left Wall-plates, when not of sufficient length to go the whole length of the wall, are connected by scarfs (fig. 276), a wedge-shaped piece being cut out of each end, so as to fit one another when connected; and where they return at angles the connection is then made by halving, or bevelled halving, the two ends, as shown in fig. 277.
The halving process consists of cutting a piece off the end of each plate, across their entire width, and to half their depth; while in the bevelled halving the remaining parts are bevelled alternately, to fit one another and prevent any displacement of the joint.
The dove-tailed notch is made by cutting halfway into each plate, with one side of each plate left straight and the other dovetailed, to prevent its being drawn out, as fig. 278.
The joists are generally spiked on to the wall-plates, or they are notched and nailed on to the plates (fig. 279).
Another method of attaining the same object is by cogging - though it is seldom used except for beams - when a "notch" is made in the underside of the beam, which fits on to a piece left on the wall-plate, which is similar to the cog of a wheel; whence the method is called "cogging " (fig. 280).
The joint between the trimmer and the trimming joists is called a tusk tenon, and illustrated by fig. 281, where it will be seen that the tenon, T, with the horn, H, and tusk, K, are cut out on the trimmer and let into a similar mortise, with the bearing or shoulder, S, on the trimming joist After they have been tightened up together, in situ, a pin, P, is driven through a mortise in the tenon, T, as shown on the plan, fig. 282.
The trimmed joists are framed into the trimmer by means of a joint similar to the last, only without the tenon being pinned, as shown in Single naked flooring can be made quite strong enough for ordinary purposes over spans up to 16 feet, the strength of the floor depending chiefly on the depth of the joists, the safe strength and depth of which cm be ascertained by "halving the span in feet, calling the quotient inches, and adding 2, which gives the depth required in inches." For example: the span being 10 feet, 10 feet ö2 = 5 inches; 5 inches + 2 = 7 inches; therefore the depth must be no less than 7 inches, and the width 2 1/2 or 3 inches, according to circumstances; although little depends on the width, which is usually either 2, 2 1/2, or 3 inches. Trimmers and trimming joists of course need to be stronger, and it is usual to add 1 inch in thickness for them, or 1/8th of an inch for every trimmed joist which need only be the same as the common or bridging joists.