Fig. 56 represents a partition having a door in the middle. Its construction is simple but effective. Fig. 57 shows the manner of constructing a partition having doors near the ends. The truss is formed above the door-heads, and the lower parts are suspended from it. The posts a and b are halved, and nailed to the tie c d and the sill ef. The braces in a trussed partition should be placed so as to form, as near as possible, an angle of 40 degrees with the horizon. The braces in a partition should be so placed as to discharge the weight upon the points of support. All oblique pieces that fail to do this should be omitted.

Fig 57.

Fig 57.

201 Examples Of Partitions 87

Fig. 58.

When the principal timbers of a partition require to be large for the purpose of greater strength, it is a good plan to omit the upright filling-in pieces, and in their stead to place a few horizontal pieces, as in Fig. 58, in order that upon these and the principal timbers upright battens may be nailed at the proper distances for lathing. A partition thus constructed requires a little more space than others; but it has the advantage of insuring greater stability to the plastering, and also of preventing to a good degree the conversation of one room from being overheard in the adjoining one. Ordinary partitions are constructed with 3x4, 3x5, or 4x6 inch joists, for the principal pieces, and with 2x4, 2x5, or 2x6 filling-in studs, well strutted at intervals of about 5 feet. When a partition is required to support, in addition to its own weight, that of a floor or some other burden resting upon it, the dimensions of the timbers should be ascertained, by applying the principles which regulate the laws of pressure and those of the resistance of timber, as explained in the first part of this section, and in Arts. 196 to 199 for framed girders. The following data may assist in calculating the amount of pressure upon partitions:

Weight Upon Partitions

White-pine timber weighs from 22 to 32 pounds per cubic loot, varying in accordance with the amount of seasoning it has had. Assuming it to weigh 30 pounds, the weight of the beams and floor-plank in every superficial foot of the flooring will be -

6 pounds when the beams are 3x8 inches, and placed 20 inches from centres

7 1/2

"

"

"

3

x

10

"

"

18

"

"

9

"

"

"

3

x

12

"

"

16

"

"

11

"

"

"

3

x

12

"

"

12

"

"

13

"

"

"

4

x

12

"

"

12

"

"

13

"'

"

"

4

x

14

"

"

14

"

"

In addition to the beams and plank, there is generally the plastering of the ceiling of the apartments beneath, and sometimes the deafening. Plastering may be assumed to weigh 9 pounds per superficial foot, and deafening 11 pounds.

Hemlock weighs about the same as white pine. A partition of 3x4 joists of hemlock, set 12 inches from centres, therefore, will weigh about 2 1/2 pounds per foot superficial and when plastered on both sides, 20 1/2 pounds.

Roofs