In each of these equations the first factor is the number of rods in a fully continuous interior bay; the second, the length in feet of the rods; and the third, their weight in pounds per linear foot. Having now computed the weight of steel per square foot of floor-area for a fully continuous interior bay, it remains to consider the end bays and corner bays. If the estimate is made upon a fully-detailed design, the reinforcement for these portions of the floor is tabulated in the same manner as for the interior bay; but if, as is often the case, the Estimator has only an interior bay fully designed, the weights for the other portions of the floor are obtained by adding a percentage to the weight of the steel, as tabulated for the fully-continuous portions. This is approximately 60% for corner bays and 30% for end bays for the conditions assumed in this design. These factors remain quite constant for all designs based upon the same code and, when once determined, greatly facilitate the computations, which should be arranged as follows: In this computation 320 is the full length of the spandrel-beams in feet, in this case the perimeter of the building, no deduction being made for columns; 10.75 is the weight of the longitudinal reinforcement of the beams in pounds per linear foot; and 1.55 a factor to allow for laps, bends, and stirrups. This factor varies between 1.30 and 1.60 depending upon the design and the proportion of continuous beams. It can be easily approximated for any particular set of conditions. As in the previous computations the total reinforcement in the spandrel-beams is reduced to a square foot basis, by dividing by the net. floor-area in square feet. Stair-beam (36 ft 13.60 lb x 1.50)/5 660 sq ft = 0.13 lb per sq. ft of floor-area in which 36 is the approximate total length in feet of all stair-beams on this floor; 13.60 is the weight in pounds per linear foot of the 4 sq in of steel which constitutes the average longitudinal reinforcement. 1.50 is a factor to allow for laps, bends, and stirrups. As these beams are not continuous it is apparent that this allowance is required principally in the form of stirrups. Additions are made for any special beams which are a part of the floor construction. There is added for incidentals, 0.20 lb per sq ft of floor-area = 4.89 lb. Total steel per square foot of floor-area Total steel in 1st structural floor 5 660 sq ft X 4.89 lb = 27 675 lb. The quantities for the roof are computed in a similar manner. = 10. Stairs. The forms for concrete stairs are often priced per linear foot of riser; another method, however, is to employ an entirely ARBITRARY NUMERICAL UNIT determined by adding to the number of linear feet of risers one-half the area of landings. All cost of form-work for posts and stringers is included in this unit. The concrete-volume is computed by adding together the volumes of all the members; and the steel-weight by counting the individual bars of a typical run. Some estimators include the cost of concrete and steel with that of the forms in one price, obtaining merely a quantity expressed as the number of linear feet of riser; ordinarily, however, it is better to separate the concrete and steel adding these into the like materials from the other elements of the work. In case the stairs are not detailed on the drawings at the time of making the estimate, the following method gives a close approximation for average conditions, and meets the requirements of the New York City Code: Forms: (12 X 4.83 ft X 1.7) + (9 × 10)/2 = 143 equivalent sq ft Concrete-volume: X In these equations 12 is the full story-height in feet; 4.83 the length of the stair treads in feet; 1.7 a factor depending upon the value assumed for the riser-height; (9 X 10)/2 one-half the landing-area, or landings, in square feet; and 0.75 and 3.00 two factors based on standard construction, with 100 lb per sq ft live load and average story heights. Special factors can be easily developed from typical designs to meet the requirements of any particular code. 11. Sills, Mullions, Copings, and Cornices. The CONCRETE-VOLUME is expressed in cubic feet, and obtained by computing the sectional area of each member in square feet and multiplying by its length in feet. For large cornices it is often necessary to divide the cross-section into triangles, or trapezoids, in order to more simply determine the sectional-area. In the case The FORM-AREA for these members is expressed in linear feet. of cornices, the contact-area in square feet should also be found. In all cases a rough sketch should illustrate, approximately, the amount of detail work required. The STEEL-WEIGHT is computed in pounds by counting the number of bars of various sizes in a typical cross-section, and is added to the weight of general reinforcement required for the job. 12. Floor and Wall Finishes. The quantity for granolithic floor finish is computed in square feet. The same unit is employed for estimating wall finishes and the area should include the faces of columns, spandrel-beams, etc., back to the face of the sash or panel-wall. 2. UNIT PRICES 1. General Considerations. Having determined the quantities and the time available for delivery, preliminary quotations can be obtained on the materials required for construction. The general plan of the plant to be employed, the probable date on which the work will commence, and the speed of operation all play important parts in regard to the delivery of the materials, and they should be decided upon, as far as possible, at this time. Obviously, if a job must start immediately upon the award of the contract, the materials required for the earlier stages of the work have to come from dealers' stocks, and advantage cannot be taken of mill shipments; likewise, the size of the operation and the storage-facilities may require a number of partial deliveries of the concrete-aggregate, and preclude the use of barge delivery, even where water transportation is available. Furthermore, the speed demanded often governs the amount of form-lumber required. At the time of making the estimate it is seldom advisable to draw up a lumber-schedule or to make detailed steel lists; but all the more important materials should be approximated in order to insure valid quotations and obviate the possibility of overrunning the dealers' protections on a rising market. This can be done by reference to the QUANTITY-SHEET. After the quotations have been obtained and recorded in the right-hand column, the Estimator next determines the probable LABOR-UNITS from a study of the COST-REPORTS upon similar classes of work. Noting these in the column provided, he has at hand all the information necessary to develop the UNITPRICES for each item of the estimate. For purpose of illustration it is assumed that the following material quotations and labor-units have been obtained. It should be noted that the prices are used MERELY BY WAY OF ILLUSTRATION and do not represent actual costs. 2. Assumed Material-Prices and Labor-Units. Material-prices from dealers: Cement, $3.00 per bbl, net, f.o.b. cars at the job-siding. Crushed stone, $2.00 per ton, delivered to job by truck. Grit, $3.00 per ton, delivered to job by truck. Form-lumber (the average price including extras and after deducting any assured salvage value), $45.00 per 1000 sq ft, board measure, f.o.b. cars at the job-siding. Steel-reinforcement, $3.00 per cwt, f.o.b. cars at the mill (on base sizes, 3/4-in square or 3/4-in round and larger). Average extras, $0.20 per cwt. Freight, $0.40 per cwt, from mill to job-siding. White cement, $6.00 per bbl, net, delivered to job by truck. White sand, $4.00 per ton, delivered to job by truck. Labor-units from cost-records: Receiving form-lumber, No. 6, $3.00 per 1 000 sq ft, board measure. Receiving sand, No. 7, $0.20 per cu yd. Receiving crushed stone, grit and cinders, No. 7, $0.20 per ton. Receiving reinforcement, No. 9, $0.10 per 100 lb. Making forms, No. 1, $30.00 per 1 000 sq ft, board measure. Placing footing-forms, No. 2, $0.10 per sq ft. Placing column-forms, No. 3,,$1.70. per lin ft. Placing floor-forms, No. 4, $0.12 per sq ft (Girderless type). Placing wall-forms, No. 5, $0.15 per sq ft. Concrete, mixing, conveying, and depositing, No. 13, $3.00 per cu yd. Floor-finish, monolithic, No. 20, $0.03 per sq ft. Floor-finish, non-monolithic, No. 21, $0.04 per sq ft. Exterior finish, No. 22, $0.025 per sq ft (brush coat). The Chapter on COST ANALYSIS should be referred to for the exact definition of each LABOR-CLASSIFICATION. The quantities of materials for various concrete mixtures may be computed as described on page 544. 3. Concrete. Assuming that for each cubic yard of rammed concrete there are required 1.60 barrels of cement, 0.45 cu yd of sand and 0.90 cu yd cf crushed stone, the computation is arranged as follows: (1) Cement, 1.60 bbl X ($3.00 + $0.15 + $0.08) (2) Sand, 0.45 yd X ($1.50 + $0.20) (3) Crushed stone, 0.90 yd X ($2.60 + $0.26) (4) Power and water (5) Mixing, conveying, and depositing (see Chapter XVII, Unit price (labor and material) = (1) 1.60 number of barrels of cement required for 1 cu yd of rammed concrete including an allowance for grouting, etc. $3.00 net price of cement per barrel, f.o.b. at the job-siding. If trucking is required, the cost per barrel is entered here: = = $0.15 receiving cement (see Chapter XVII, Labor-Classification (8)). $0.08 cost of testing cement ($0.03), and bag-loss ($0.05) per barrel, including the cost of baling and returning the empty bags. (2) 0.45 = number of cubic yards of sand required for one cubic yard of rammed concrete. = $1.50 price per cubic yard of sand delivered to job. If trucking is required, the cost per cubic yard is entered here: $0.20 receiving sand (see Chapter XVII, Labor-Classification (7)). = (3) 0.90 = number of cubic yards of crushed stone required for 1 cu yd of rammed concrete. = $2.60 price per cubic yard of crushed stone delivered to job (price per ton X 2620). If trucking is required, the cost per cu yd is entered here: $0.26 = receiving crushed stone per cubic yard (cost per ton X 220) (see Chapter XVII, Labor-Classification (7)). (4) Allowance for power ($0.15), and for water ($0.10). (5) Allowance for labor-cost (see Chapter XVII, Labor-Classification (13)). The price of $0.44 per cubic foot is then applied to the entire volume of concrete, of the same mixture, as the unit labor-cost of classification No. 13, namely $3.00 per cu yd, is based on cost-data covering the AVERAGE COST of mixing, conveying, and depositing the concrete FOR AN ENTIRE JOB, from footing to roof. For other mixtures the proportions of cement, sand, and gravel, required for 1 cu yd of rammed concrete, are determined as on page 544. 4. Forms. The unit used for form work takes into consideration not only the cost of lumber, nails, grease, etc., but also the waste, and the number of times that the forms are to be used. Bearing these points in mind, the cost of material and labor in MAKING FORMS is first computed as follows: For floors, of flat-slab type each 1 000 sq ft of form-area require 4 000 to 5 000 sq ft of form-lumber, besides that needed for re-posting. Assuming the former value to be correct in this case, the making of such forms cost, $0.084 X 4 = $0.336 per sq ft of FORM-AREA If the floor-forms are to be used twice the result is: Cost of making girderless floor-forms AREA. = $0.336/2 $0.168 per sq ft of FLOOR Similarly, if 5 000 sq ft of lumber is required for 1 000 sq ft of floor-forms for a beam-and-girder construction, the making of such forms cost This value is then divided by a figure representing the number of uses to give the cost per square foot of floor-area. It should be noted that this allowance includes all beams and girders and that the floor-area is based on the HORIZONTAL AREA of the floor. An allowance of 6 sq ft board-measure per square foot of |