CAR
88
CAR
may be placed 12 or 14 inches distant, their scantling 3 and4, or 3-Jr and 5, their bearing being only from binding-joistto joist, which is 3 feet, or 3 feet 6 inches, and these arelaid even with the top of the girder, to receive the boarding.We come now to speak of girders; and first, for theirscantling, take these proportions :
ft. long
Scantling ininches.
B. D.
10
8 by 10
12
8J by 10
14
9 by 104
16
94 by loj
18
10 by 11
20
11 by 12
22
114 by 13
24
12 by 14
“ And observe, that as every freight, added to the weightof the timber in the floor, in itself occasions it to settle, thegirders should be cut camber; if a 10 feet bearing, half aninch camber; if 20 feet bearing, an inch camber, &c., in pro-portion to the length of the bearing.
! “ And farther to strengthen the girder, and prevent its
j sagging, as it is called among workmen, that is, its bendingI downwards, I have given you several ways of trussing gir-I ders, which have been most of them practised.
“ The manner of trussing these girders, is, first, to sawthe girder down the middle, the deepest way; then take twopieces of dry oak, about 41 or 5 inches wide, and 4 inchesthick; let half the piece be let into one side of the girder andhalf, into the other.
“ Another way, which is by cutting the girder through,and driving a wedge against the ends of the trusses. Whenthese are thus prepared, bolt them together with iron boltsand keys; or much rather, a screw at the end of the bolt.
“ Some carpenters cut their girders down the middle, andbolt them together, without trussing, only changing the endsdifferent from what they grew, whereby the grain of the woodis crossed, and it becomes much stronger than if it had con-tinued without sawing down the middle, hnd thus putting ittogether. ,
“ Some, in trussing girders, make use of other trusses.
“ The girder being thus trussed and put together, proceed■ in framing the joists, as in common floors. The strongest wayI | being double-tenanting and tusking, as is shown in the bind-j ing-joists. Before I leave this part of floors, I shall observe| to you, that the best and most workmanlike manner of
I framing floors, is to plane the upper edge of your joists
I straight; for the straighter and truer your joists lie, the trueryour boarding will lie, which is a great ornament to a mag-nificent room; but if you frame without binding-joists, andlay on bridgings, plane the bridgings, and lay them verystraight and level; this care taken will save a great deal oftrouble in laying down the boarding, which you are oftenforced to chip and fur up, to make them lie even, and thosej furrings are not only troublesome, but are apt to give way,
■ and occasion the creeking of the boards as you walk on them.
| It would be a good way to turn arches of brick over the endsI of the girders of the floors, because if any alteration happens,
| they are easily taken out.
“ I come now to partitions of timber, with their mannerI of framing. Timber partitions have these properties attend-! | ing them; they take up less room, and are cheaper than thosej : of brick.
" As to roofs, there is a plate to go round a building, which
may or may not be deemed a part of the roof; it may bedeemed the foundation and tie of the roof and walls; or itmay be taken as only that on which the roof lieth. Theseplates are to be dovetailed at the angles, and tenanted toge-ther in their length, several ways. The beams of the roof,which serve as girders to the ceiling-floors, (and into whichall the principal rafters of the roof are tenanted) are dove-tailed, or what by workmen is termed cogged down, to theplate, which prevents its flying out from the foot of therafter, whose hutment is against it; and in the angles of *building, pieces dovetailed across the angles of the plate,serve to keep it from spreading, and is the foot of the hip.
“ The common pitch of roofs is to have the rafter’s length,if it span the building at once, to be three-fourths of thebreadth of the building. Some make them flatter, as a pedi-ment pitch; and the old Gothic way was to make them thewhole breadth.
“ The common pitch is not only unpleasing to the eye, butis attended with this inconvenience; if there is a gutterround the building, the steepness of the roof occasions therain to come with so sudden a velocity into the pipes whichare to convey the water from the gutters, that they fill thegutter; and sometimes so fast, that the water runneth overthe covering of the roof, and does great injury to the tim-ber, &c., of the building; and the steeper the roof is, thelonger the rafters, and the greater quantity of timber mus 4be used in the roof, as well as the more weight from the gre® 4quantity of timber, and the weakening the principal timbers,by adding more to its own weight.
“ And the pediment pitch is inconvenient, in lying toeflat, for those climates so frequently subject to rain, aimheavy snows, which last would press and vastly incomrnod®the building, and would lie much longer on the roof, l4 jdeclivity being so small; besides, in keen winds, attendewith rain, the rain would drive in under the covering of sla 4eor tiles, and create much decay in the timber.
“ Proportion of beams whose bearing varieth ; take 441following rule:
Scaiitling ininches.
12
6
by
8
16
6 i
by
8 £
20
64
by
9
24
7
by
94
28
H
by
9J
32
8
by
10
36
84
by
104
40
8i
by
11
44
9
by
12
S i
I
I
I
“ The principal rafter should be nearly as thick at ofbottom as the beam, and diminish in its length one-fi* 4 ,one-sixth of its breadth ; the king-posts should be as 4 ’ ^as the top of the.principal rafter, and the breadth accor j
to the bigness of the struts you intend to let into them, ^ j
middle part being left something broader than the thickn“ Struts may diminish, as the rafters do, one-fifth or 0sixth of their length. In placing struts and collar-beams, ^dividing the rafter into as many equal parts as you proP^.jj jbearings, is the rule, because every part of the principalhave its equal distant bearings. c ie x, j
“ Purlins are of the same thickness as the principal ra |and the proportion of the breadth is six to eight; that 1 ’ g jthe rafter be six inches thick, let, the purlins be six m i
thick, and eight inches broad; if it be nine inches thick, !
breadth of the purlins is twelve inches broad, &c.