=42. Carpentry= should include general framing, roofs, floor joists,
partitions, sheathing, flooring, furring, and plastering grounds.
=43. Board Measure.=—The rough lumber used in framing is measured by
the =board foot=, which means a piece 12 inches square and 1 inch
thick. Lumber is always sold on a basis of a thousand feet =board
measure=. The customary abbreviation for the latter term is B. M.; that
for _thousand_ is M. Thus, 500 feet board measure, costing $27 per
thousand, would be written: 500 ft. B. M., at $27 per M.
To obtain the number of board feet in any piece of timber, the length,
in inches, should be multiplied by the end area, in square inches, and
the result divided by 144. For example, the number of feet B. M. in a
floor joist 20 feet long, 3 inches thick, and 10 inches deep is 240
inches (=20 feet × 12) multiplied by 30 square inches (the end area)
divided by 144, or 50.
The following rule is used by most contractors and lumber dealers:
_Multiply the length in feet by the thickness and width in inches, and
divide the product by 12._ Thus, a scantling 26 feet long, 2 inches
thick, and 6 inches wide contains
26 × 2 × 6
---------- = 26 feet B. M.
12
This rule, expressed in a slightly different manner, is more convenient
for mental computation: _Divide the product of the width and thickness
in inches by 12, and multiply the quotient by the length in feet._
Thus, a 2" × 10" plank, 18 feet long, contains
2 × 10
------- = 30 feet B. M.
12 × 18
=44. Prices of Lumber.=—Owing to the continual variation in the prices
and grades of lumber, it is impossible to give prices here that will
not vary from day to day. The architect before starting to estimate
should first be sure that he has the latest lumber prices obtainable.
These prices can always be secured from the local lumber dealer.
=45. Studs.=—To calculate the number of =studs=—set on 16-inch
centers—the following rule may be used: _From the length of the
partition, in feet, deduct one-fourth, and to this result add 1. Count
the number of returns, or corners, on the plan, where double studding
is required, and add 2 studs for each such return._ (The reason for
adding 1 is to include the stud at the end, which would otherwise
be omitted.) The sills, plates, and double studs must be measured
separately.
[Illustration: FIG. 4]
For example, the number of studs required for partitions only, shown on
the plan, Fig. 4, is computed in the following manner.
30 ft. 6 in.
10 ft. 6 in.
9 ft. 6 in.
5 ft. 0 in.
4 ft. 6 in.
------------
60 ft. 0 in.
Deducting one-quarter from 60 feet,
the remainder is 45 feet; adding
1 stud, the result is 46 feet. As
there are 4 returns, with 2 studs
for each, as shown at _a a_, the
total number is
46 + (4 × 2) = 54 studs.
As a general rule, when (as is customary) the studs are set at
_16-inch_ centers, _1 stud for each foot_ in length of partition will
be a sufficient allowance to include sills, plates, and double studs.
Thus, if the total length of partitions is 75 feet, 75 studs will
be sufficient for sills, double studs, etc. If the studs are set at
_12-inch_ centers, the number required will be equal to the _number
of feet in length of partition plus one-fourth_. Thus, if the length
of partitions is 72 feet, 72 + 18, or 90, studs will include those
required for sills, plates, etc.
The same rules may be used for calculating the number of joists,
rafters, tie-beams, etc.
A good way to estimate bridging is to allow 3 cents apiece, or 6 cents
per pair; this will be sufficient to furnish and set a pair made of 2"
× 3" spruce or hemlock stuff.
=46. Sheathing.=—To calculate =sheathing= or =rough flooring= (not
matched), find the number of feet B. M. required to cover the
surface, making no deductions for door or window openings, because
what is gained in openings is lost in waste. If the sheathing is laid
horizontally, only the actual measurement is necessary; but if it is
laid diagonally, add 8 or 10 per cent. to the actual area.
=47. Flooring.=—In estimating =matched flooring=, a square foot of
⅞-inch stuff is considered to be 1 foot B. M. If the flooring is 3
inches or more in width, add one-quarter to the actual number of board
feet, to allow for waste of material in forming the tongue and groove;
if less than 3 inches wide, add one-third. Flooring of 1⅛-inch finished
thickness is considered to be 1¼ inches thick, and for calculating it
the following rule may be used: _Increase the surface measure 50 per
cent._ (This consists of 25 per cent. for extra thickness over I inch,
and 25 per cent. for waste in tonguing and grooving.) To this amount
add 5 per cent. for waste in handling and fitting.
In figuring the area of floors, openings for stairs, fireplaces, etc.
should be deducted.
=48. Weather Boarding, or Siding.=—In measuring =weather boarding=,
or =siding=, the superficial, or square, foot is usually employed. No
deduction should be made for ordinary window or door openings, as these
usually balance the waste in cutting and fitting. Careful attention
must be given to the allowance for lap. If 6-inch, nominal width
(actual width, 5⅝ inches), siding, laid with 1-inch lap, is used, add
one-quarter to the actual area of the space to be covered, in order to
obtain the number of square feet of siding required. If 4-inch stuff is
used, add one-third to the actual area. When, as previously noted, no
allowance is made for openings, the corner and baseboards need not be
figured separately.
=49. Cornices.=—As a general rule, cornices are measured by the running
foot, the molded and plain members being taken separately. A good
method of figuring cornices is as follows: _Measure the girth, or
outline, and allow 1½ cents for each inch of girth, per linear foot._
This price will pay for material and for setting, the cost of the mill
work being estimated at 50 per cent.
=50. Cost per Square Foot.=—For all classes of materials that enter
into the general framing and covering of a building, a close estimate
may be made by analyzing the cost per square foot of surface; that is,
the cost of labor and materials—studs and sheathing in walls, joists
and flooring in floors, etc.—required for a definite area should be
closely determined, and this cost divided by the area considered, will
give the price per square foot. If the corresponding whole area is
multiplied by the figure thus obtained, the result will, of course,
be the cost of that portion of the work. While the usual custom is to
adopt a uniform rate for the various grades of work, a careful analysis
will show that roof sheathing, where the roof is much cut up, costs
more in place than wall sheathing, owing to its position; also that the
studs in walls and partitions cost more than floor joists, as they are
lighter and require more handling.
The following example shows how to determine the cost per square foot
of flooring and indicates the general method to be pursued in similar
cases. The area used in the calculation is a square, or 100 square
feet. The cost of labor is estimated at 40 per cent. of that of the
materials, as it has been shown by experience that this allowance is a
very close approximation to the actual cost of general carpenter work.
COST OF FINISHED FLOOR PER SQUARE
Joists, hemlock, 8 pieces, 3" × 10" × 10',
200 feet B. M., at $27 per M. $ 5.40
Bridging, hemlock, 7 sets, 2" × 3" × 1' 4",
9 feet B. M., at $27 per M. .24
Rough flooring, hemlock, ⅛ inch thick, laid
diagonally, 100 ft. + 25 ft. + 10 ft.,
135 feet B. M., at $25 per M. 3.38
Finished flooring, No. 2, white pine, ⅞ inch
thick, 125 feet B. M., at $45 per M. 5.63
Nails, eightpenny (about) 3 pounds, at $2.50
per 100 pounds .08
Labor, 40 per cent. of cost of materials 5.89
------
Total cost for 100 square feet $20.62
Cost per square foot, $20.62 ÷ 100 = 21 cents.
A similar method may be followed in estimating the cost of interior
finish, paneling, doors, etc.
=51. Work of a Carpenter per Day.=—The quantity of material that a
workman can put in place in a day is very uncertain, as it depends on
the skill of the man and the ease or difficulty of the work, both being
somewhat modified by circumstances. The figures given in Table VI,
while founded on information gained by many years of experience, are
only intended to give an idea of the relative quantities and are not a
standard to be adhered to in all cases. The estimates are based on an
8-hour day and wages at $3.20 per day. If the hours or pay are less or
greater in various localities than the prices given, the results will
be correspondingly diminished or increased.