Fig. 162 shows the forms for the columns. The planks for each side of the column arc held together by the 1 by 4-inch strip, and, when erected in place, are clamped by the 2 by 4-inch strip. A large opening is left at the bottom of each column, so that all shavings and sawdust can be removed. This opening is closed just before the concrete is dc posi ted.
355. Cost of Forms for Buildings. An analysis of the cost of forms for an eight-story build ing is given by R. E. Lamb (Con crete Engineering, December, 1907). The basis of his estimate is made on using .A-inch by 6-inch tongued-and-grooved lumber for slab forms; l ;-inch dressed plank for the sides and bottom of the beams and girders; posts 4 by 4-inch spaced 6 feet center to center; and on the fact that it cost $20.00 per thousand feet of lumber to make and set one floor of forms; that it cost $15.00 per thousand feet to strip the forms and reset them on the next floor; and that it cost about $8.00 per thousand feet to strip the forms and lower them to the ground.
With the size of the beams and girders as shown in Fig. 163, Mr. Lamb states that it will take an average of 4 feet, board measure, to erect each square foot of floor area. The basis of his esti mate is as fol lows: that 1.5 board feet of lumber per square foot of floor is required for the slab; that for every square foot of beam sur face, including the bottom, 3.2 board feet per square foot is re quired; and that for each square foot of girder, including the bottom, 3.6 board feet of lumber is required. Taking these figures, for the panel shown, the slab will require 1.5 board feet per square foot; the beams, which are S by 18-ineh, will have 3 feet S inches of surface per linear foot; and multiplying this by 3.2 board feet per square foot, and dividing by 7.5 feet, the distance center to center of beams, we find that 1.56 board feet per square foot of floor face is required. Taking the girder in the same way, with 4 feet S inches of surface, plied by 3.6 board feet, and divided by 18 feet, the distance center to center of girders, we find that .94 board foot per square foot of floor is required. The total of the lumber required, then, is 1.5 board feet for the slab, 1.56 board feet for the beam, and .94 board foot for the girders—a total of 4 board feet per square foot of floor area.
In this estimate for an eight-story building, three sets of forms were used: Roof: Stripping the sixth floor, resetting, altering to form valleys, and finally stripping roof and lowering forms to ground, 4 board feet at 2.6 cents $ . 104
Eighth Floor: Stripping the fifth floor, resetting, and finally stripping and lowering forms to ground, 4 board feet at 2.3 cents .092 Seventh Floor: Stripping the fourth floor, resetting, and finally stripping and lowering forms to ground, 4 board feet at 2.3 cents .092 Sixth Floor: Cost, same as for the fourth floor .060 Fifth Floor: Cost, same as for the fourth floor .060 Fourth Floor: Stripping the first floor, and resetting, 4 board feet at 1.5 cents .060 Third Floor: Cost, same as for the first floor .154 Second Floor: Cost, same as for the first floor .154 First Floor: Making and setting forms, 4 board feet at 2 cents $.080 Material, 4 board feet at 2.6 cents .104 .184 9 T1.020 Average cost per square foot of surface $ .113 To this average cost of 11.3 cents, 10 per cent should be added for waste, breakage, nails, etc.; and if two sets of forms are used, the third floor would cost 6 cents per square foot, and the seventh floor 6 cents, giving an average of 9.6 cents per square foot.
In estimating the cost of the forms for the columns, it is assumed that making and placing the forms for the basement columns will cost about $26.00 per thousand; the cost of stripping and resetting, $16.00 per thousand; and 3.1 square feet of lumber is required for each square foot of column surface.
Eighth Story: Stripping sixth story, resetting and altering, finally stripping eighth story, and lowering to ground 3.1 board feet at 2.2 cents S .06S Seventh Story: Stripping fifth story, resetting, and finally stripping and lowering to ground 3.1 board feet at 1 9 cents .059 Sixth Story: Cost, same as second story .050 Fifth Story: Cost, same as second story .050 Fourth Story: Cost, same as second story .050 Third Story: Cost, same as second story .050 Second Story: Stripping basement columns and resetting 3.1 board feet at 1.6 cents .050 First Story: Cost, same as for the basement columns . 162 Basement: Material, 3.1 board feet at 2.6 cents $.OS1 Making and setting 3.1 board feet at 2.6 cents .0S1 .162 .1629 ) .701 Average cost per square foot of surface S.077 To this average cost of 7.7 cents per square foot of column surface, should be added 10 per cent for bolts, nails, waste, etc. If three sets of forms are required, the second-story cost would be 16.2 cents, and the sixth story 5.9 cents, giving the average cost per square foot, of 9.1 cents.