Imagens das páginas
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11' 4" 18' 4" 11′ 43′′ 11′ 734" 18′ 94" 11′ 7′′ 11' 11" 19' 3" 11' 11" 12′ 24′′ 19′ 84" 12′ 24′′ 12′ 51⁄2" 20′ 11⁄2" 12′ 51⁄2" 12′ 834" 20′ 64" 12′ 8%" 13' 0" 21' 0" 13' 0" 13' 34" 21' 54" 13' 34" 13' 6" 21' 10" 13′ 13' 9" 22′ 34" 13′ 934" 14' 1" 22' 9" 14' 1"

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23′ 24′′ 32′ 04′′

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6' 71⁄2"

3' 10"

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37' 11"

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The values given in foregoing nail table are for average lengths of wood, double nailed at the ends and single nailed at intermediate points. Where end joints occur, both abutting ends are usually double nailed, and for that reason, the number of nails for a given work will vary with lengths of the boards used. When large surfaces are estimated, it is often worth while to develop the actual number of nails which can be resolved into pounds by using the following weights:

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It is convenient to group all nails and other hardware in the estimate, omitting these at the time the carpentry is listed.

Wood nailers are frequently used on steel members for fastening corrugated iron, wood roofs, millwork, etc. For ordinary roof decks, 2 X 4 or 2 × 6-in. nailers are commonly used with a 3 X 4 or 3 X 6 wherever ends of roof boards butt together and double nailing occurs. 2-in. carriage bolts are usually estimated on 18 to 36-in. centers. Material and labor are figured by the thousand feet board measure. The main feature in determining the labor allowance may be the possibility of bolting the nailer before the steelwork is erected. Nailers attached to steel members after erection may cost from 50 to 150 % more.

Roof Decking. The cost of applying roof planking like all other roofing operations depends mostly upon the slope of the roof and the extent to which the roof surface is broken up. On a flat roof where the carpenter need

take no precautions against sliding, the work is carried on at a faster pace. Height of roof will also influence the cost. If the roof is too high to permit workman on the ground to hand the boards up to the men above, costs of hoisting are included. For factory buildings it is more a case of hoist or no hoist, as there is no appreciable difference in the cost for raising lumber 25 or 65 ft. The unit cost may be estimated as follows:

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Temporary end or side framing of studs and sheathing, or studs and siding, is often estimated for steel factory buildings when the owner anticipates further expansion. The material (studding and surfacing) is generally listed and estimated as two separate items, resolved into feet board measure, priced and extended by the thousand. To arrive at the labor cost of this kind of framing, some estimators apply a price per square foot covering both the siding and studding costs. The labor cost for studding usually runs more, however, and by separate listing more accurate units are employed.

Interior Trim.-The costs of the various moldings used for interior trimming unlike most branches of carpentry, are frequently based on a price per lineal foot, both the material and labor costs being made up on this basis. The material includes the gross size of the section planed plus the cost for running the board through the mill. Plain sections cost about the same as fancy ones, providing there is the same number of machining operations. The labor costs include the use of finishing nails set into the wood so that the holes may later be puttied over by the painter.

16. Painting. Painting is estimated by units of area, sometimes 1 sq. ft., 1 sq. yd., or 1 square. The unit-1 square-seems most practical because, if anything, it is easier to develop a price per 100 sq. ft. than a price for 1 sq. ft. Furthermore, to maintain the same accuracy, a unit per square foot must be carried into several more decimal places, and this seems like unnecessary detail. In arriving at the number of squares, the take-off includes the gross areas to be covered. Like all other operations, surfaces with varying unit costs are taken off separately so that the correct unit price may be speedily approximated for the several items, each of which includes only one class of work. Each list bears a caption fully describing the material and the number of coats the surface is to receive. When listing the painting of glazed doors and windows, no deduction is made for the glass. The extra cost of painting the narrow striping balances the saving of material. It is well, however, to note the area of this kind of surface in the event the exact amount of paint will have to be determined later. The labor conditions are best derived by reference to the drawings.

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The increased covering or spreading value of the zinc paint does not represent any economy over the use of lead paint, as the zinc will not usually cover as effectively as the lead. Up to 10% of dryer may be used to force the chemical action of the drying and lessen the drying time of the first coat, but dryers are seldom estimated as an ingredient of the last two coats as it is generally known that the wearing quality of paint is impaired proportionately with the amount of dryer added. Similarly, glue size as a first coat is estimated only for the cheaper grades of work. The cost of glue size is about 5% of that of good paint but it will not adhere nearly as well as a first coat of thin paint. The unit cost of painting for common classes of work is usually understood to include scaffold labor. In only rare instances does a painter do any work for which no ladders and staging are necessary.

17. Composition Roof Coverings.—Roofing is generally estimated by the square-that is, a unit of 100 sq. ft. The roof surfaces are listed in the estimate allowing about 1 ft. at

parapets, or more when specified, and the area resolved into squares. As the average general contractor usually purchases roofing in place from the roofers, quotations are generally used for pricing the estimate. The unit price as quoted by the roofer having a specified type and weight of roofing in mind, would depend on the pitch of roof, height, number of separate roofs into which the area may be divided, and the construction of the roof deck. A roof is generally termed steep or flat depending upon whether roof ladders need be used. The division occurs in the neighborhood of 14 pitch.

18. General Field Expenses. After all of the building operations have been included in the estimate, a summary is made of the costs for conducting all work not a part of any specific installation. These generals may be listed separately or grouped in the following manner with the total carried over into the right-hand column as shown on sample estimate in Art. 2. Assuming a factory building costing about $800,000, these items will appear approximately as follows:

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*Insurance (Workmans Compensation and Liability) 10% of % of $800,000..

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Overheads (say 8%).

$740,741.00 59,259.00

Total cost...

$800,000.00

10% is the estimated rate of insurance for factory structures. Rates vary in different localities. is the estimated proportion of labor to the total cost of the building-in other words, the estimated payroll expenditure.

Adding field overheads to the other costs appearing in the estimate gives a total on which the general office and contracting overheads can be based. The percentage used to determine this general office overhead depends entirely upon what proportion of the organization is contained in the general office. By adding this percentage in the estimate, the net cost of the construction is established and only the allowance for profit is needed to arrive at the bidding price. Naturally the above outline will not serve for all conditions affecting estimates. Often an organization uses a smaller profit factor on sub-bids than on the work to be executed by its own forces, and in that event the estimator should use a separate column for sub-bids or have other ready means for determining at once the total amount of the work to be sublet.

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