273. Partitions, in carpentry, are frames of timber used for dividing the internal parts of a house into rooms: they are usually lathed and plastered, and sometimes the spaces between the timbers are filled in with brickwork.
In modern carpentry there is no part of a building so much neglected as the partitions. A square of partitioning is of considerable weight, seldom less than half a ton, and often much more; therefore a partition should have adequate support: instead of which it is often suffered to rest on the floor, which of course settles under a weight it was never intended to bear, and the partition breaks from the ceiling above.
If it be necessary to support a partition by other means than a direct bearing on the walls, it should rather be strapped to the floor or roof above it, than be suffered to bear upon the floor below; because in that case the cracks along the cornice would be avoided; but the timbers of the floor or roof must be made stronger. A partition ought to be made capable of at least supporting its own weight, for even when doorways are so placed that it cannot be trussed the whole depth, it is almost always possible to truss over the heads of the doors.
274. Partitions that have a solid bearing throughout their length do not require braces, indeed they are better without them, as they are easily stiffened by means of struts between the uprights, and the shrinking and cross strains occasioned by braces are thus avoided. When braces are introduced in a partition, they should be disposed so as to throw the weight upon points which are sufficiently supported from below, otherwise they do more harm than good.
Though "it be often practicable to give a partition a solid-bearing throughout, it is better not to do so, as fractures would be caused by the settling of the walls; the partition should therefore be supported only by the walls to which it is connected, so that both may settle together.
Also, when a partition is supported at one end by the wall of a high part of the building, and by the wall of a lower part at the other end, it will generally crack either close by he walls, or diagonally across; but much will depend on the state of the foundations; if they do not fail, the settlement in the walls, owing to unequal heights, will be very small.
In a trussed partition the rule is that the truss should lave good supports, either at the ends or other convenient
)laces, and the framing should be designed so that the weight may not act on any other points than those originally intended to bear it. The best points of support are the walls which the plastering of the partition joins.
275. Partitions are made of different thicknesses, according to the extent of bearing: for common purposes, where the bearing does not exceed 20 feet, 4 inches is sufficient; or, generally, the principal timbers may be made
4 inches by 3 inches for a bearing not exceeding 20 feet.
The filling-in pieces, which are called " quarterings" or " studs " when long, and " puncheons " when short, need not be thicker than about 2 inches, or just sufficient to nail the laths to.
When these filling-in pieces are in long lengths, that is, when they exceed 3 or 4 feet, they should he stiffened by short struts or horizontal pieces inserted between them, or, which is better, a continued rail notched across the uprights and nailed to each. In a brick-nogged partition these horizontal pieces, which are called " nogging pieces," are essential. They are usually much thinner than in a lath-and-plaster partition, being seldom more than three-quarters of an inch thick, and the same width as the struts, and placed at about every third or fourth course of the brickwork in height.
It should be borne in mind in all cases that useless timber is an additional load upon the framing, and only increases the risk of failure at a considerable expense.
The thicknesses above mentioned apply only to partitions that have no other than their own weight to bear. When a partition is intended to support a floor, it must be prepared for that purpose. It would, however, be impossible to lay down rules for such cases, as the design will vary according to the circumstances of each, which may differ materially.
The quarterings or filling-in timbers for a lath-and-plaster partition should be spaced at from 12 to 18 inches from middle to middle, according to the length and strength of the laths. In a brick-nogged partition the quarterings should be either 18 inches, 2 feet 3 inches, or 3 feet apart, being a multiple of 9 inches, or the length of a brick.
The arrises of all timbers exceeding 3 inches in thickness should be taken off as shown by Fig. 85, to admit of a sufficient key for the plastering.
276. The pressure in the direction of any of the pieces may be found by applying the principles given in Sect. I., and the scantlings of the timbers that would be sufficient to sustain such pressures may be found by the rules for the stiffness of materials in Sect. II. The following data will assist in forming an estimate of the pressure on the framing of partitions: -
The weight of a square of partitioning may be taken at ........
The weight of a square of single joisted flooring, without counter-flooring.. .. ..
The weight of a square of framed flooring, with counter-flooring.. .. ..
As great nicety is not required in calculating the scantlings, the highest numbers may be taken for long bearings, and the lowest for short ones; one gives the weight in large mansions, the other that in ordinary houses.
The shrinkage of timbers, and still more frequently imperfect joints, cause considerable settlements to take place in partitions, and consequently cracks in the plastering; it is therefore essential that the timber should be well seasoned, and also that the work should be well framed, as even a slight degree of settlement in a partition is attended with worse consequences than in any other piece of framing.
277. Fig. 1, Plate XXXII., shows a design for a trussed partition with a doorway in the middle; the tie or sill is intended to pass between the joisting under the flooring boards. The strongest position for the inclined pieces of the truss is shown by the figure, as the truss would have been much weaker with the same quantity of material if these pieces had been placed in the positions shown by the dotted lines. The inclination of the trussing-pieces should never greatly differ from an angle of 40° with the horizon. The horizontal pieces a a are intended to be notched into the uprights, and nailed: in partitions for principal rooms, one on each side might be used.
278. When a doorway is placed near to the side of a room, which is often necessary, in order to render the room either convenient or comfortable, the partition should be trussed over the top of the door, as shown in Fig. 2. The posts A, B, should he strapped to the truss, and braces may be inserted in the lower part of the truss in. the ordinary way; but it would be better to halve them into the uprights, which would have the effect of binding the whole together.
In order to save straps, the posts A, B, are often halved to the inter-tie C D; which, in that case, should be made a little deeper; and perhaps this is the best method, as the tie may always be made strong enough to admit of halving.
Partitions should always be put up some time before they are plastered, so that any imperfection in the joinings caused by the warping or shrinking of the timbers may be seen and rectified in time. This precaution is not so necessary where timber has been a considerable time cut to the proper scantlings, or otherwise well seasoned.