Add percentage for overheads, business generals, and depreciation of tools. 120.00 420.00 682.00 30.00 $7141.60 As the insurance is based on payroll expenditure, it is necessary to segregate all field payroll items. The estimated equipment costs must necessarily be based on the proper kind of apparatus for the type of structure to be erected. Stiff-leg and guy derricks are most commonly seen on building erection. The term "bulling" is used to indicate moving or dragging structural steel with crow bars, dolly rollers, or other make-shift methods wher the haul is not long enough to justify teaming or other more regular methods of transporting. The cost of setting up a stiff-leg derrick on the ground under favorable conditions will run from about $125 for a 70 to 85-ft. boom, 10-ton rig, to $300 for a 100-ft. boom, 20-ft. outrigger, 25-ton capacity derrick. The comparative cost for setting up a 95-ft. boom, 15-ton capacity guy derrick, with minimum of six 1-in. cable guys is from $200 to $250. An 85-ft. steel gin pole on the same basis would cost about $80. These costs are based on a wage of 872c. an hour. 50% should be added for dismantling. 34-in. diameter field rivets in factory buildings run from 12 to 15c. a piece. Simplified scaffolding and concentrated rivets as are common in bridge work or heavy loft buildings will tend to decrease these costs considerably. Labor costs for bolting are from 2 to 3 those for riveting. The painting of structural steel is approximated by the ton of material to be covered. Light weight steel will net additional and more scattered surfaces than heavy construction. Extra scaffolding often raises the price 300 %. Proportions for material and labor noted in above estimate are for medium weight shop buildings. The estimated quantity of coal depends in turn upon the estimated tonnage and the number of field rivets. For the first type of structure noted in the accompanying table, the coal would probably figure at the ratio of one ton for every 50 tons of steel, plus one ton for every 400 to 600 rivets depending upon the proper number of riveting gangs. When only one gang is working, 50 % more coal is consumed. An item covering railroad fares for such workmen as cannot be procured at the site is usually entered in the estimate. This item is mostly a matter of judgment of general building conditions and in unfavorable building localities it may even be necessary to allow for the costs of commissaries and bunk houses. Expense due to planking and use of timbers must be foreseen by the estimator. Particularly in connection with high loft building erection is temporary planking necessary around the derricks and at floors where smaller members are piled and sorted. Timbers are usually necessary for compression members in setting up derricks. Timbers are also frequently estimated when constructing additions to present buildings. It is often found necessary to support wall bearing members until new material is set in place. APPROXIMATIONS OF WEIGHTS OF STRUCTURES AND NUMBER OF SHOP AND FIELD RIVETS These are taken from actual structures and will furnish a basis for rough approximation of the different types of steel skeletons. The weights include the steel frame only, and the crane runway when noted. figures include weights of cranes or machinery. None of the Weight of steel Head frame over shaft of iron mine 125 ft. high. 15 tons working load. 100 to 200 • Weight per cubic foot of building. * Weight per lineal foot of crane travel. Total weight-light. Total weight if equipped with crushers, conveyors, etc. 11. Brickwork.-Brickwork is priced by the unit of 1000 brick (abbreviated M). A simple, accurate method for arriving at the number of brick is to list the area and thickness of each wall. Using standard size brick which are 24 X 3% x 8 in., an average of 7 bricks is estimated for each square foot of wall of thickness equal to the width of one brick. If the thickness of the wall is two bricks wide, then 14 bricks per square foot are estimated, etc. The estimated number of brick in a building is frequently designated as "wall count." This term indicates that the total wall areas have been considered without deductions for openings, such as doors and windows. It is assumed that the expense for bricking jambs, etc., around these openings is the same as the cost would be for building them solid. While this assumption may be correct, the result does not indicate the exact amount of material to be purchased. The following detailed unit cost is intended for pricing a take-off in which all openings 2 × 2 ft. or larger have been deducted. A feature for adjusting the number of brick estimated with the varying thickness of the mortar joints that may be specified, is essential. This adjustment can be made when compiling the unit price. Assuming that a standard size common brick is to be used with a 2-in. joint, the unit cost per M is made up approximately as follows: When a 2-in. joint is estimated, there are actually 6.37 brick in 1 sq. ft. of wall. In order to avoid using this ambiguous fraction in numerous extensions, it has been assumed that seven brick occur in each square foot of wall as noted in above table. Therefore, for each 1000 brick 6.37 developed by the take-off, only of 1000, or 910 brick, will really be used. This then is 7.00 the number of brick per M estimated, that will need to be purchased, and has accordingly been used in arriving at the unit price per M. A simple method that may be used for the development of this actual number of brick required for 1 sq. ft. of wall of thickness equal to one brick width, is to lay out on a drawing board 1 sq. ft. of wall including only stretcher courses. Another square foot of wall is then sketched showing only header courses. As these walls are but one brick width in thickness, the amount of brick in each is readily determined by dividing the area of the exposed faces by the area of one side of the size brick estimated. If a header course is specified at every fifth row, then the value of the number of brick in the stretcher sketch is 4 times that for the number of brick developed in the sketch showing headers. The average number of brick per square foot of wall is then determined by adding 4 times the number of brick appearing in stretchers to the number shown in headers and dividing by 5. This computation can be made for any size brick and although the result is not 100% correct, it is sufficiently accurate for any practical purpose. Further refinement would be offset by variances occurring with field operations and would be of little practical benefit. The cost of walls constructed of face brick backed up with common brick is generally estimated by first listing the entire wall as though it were of one kind of brick. A second take-off is then made of the face brick. This is subtracted from the whole to obtain the number of common brick. The unit cost for walls of brick veneer, usually a single thickness of only stretcher courses, often includes the metal ties for bonding the brick to the body of the wall. The number of brick occurring in each square foot of this veneer wall as well as in English, Flemish, or any of the other numerous bonds, is readily determined by the proper manipulation of the values developed by the sketches of stretcher and header courses as explained above. When constructing sills, corbels, soldier courses, etc., the extra labor may be estimated by allowing from 12 to 18c. per lineal foot in addition to the cost already appearing in the estimate, by including these quantities with the straight wall work. Arches likewise entail extra costs. Frequently a temporary wooden support must be built and an item of carpentry is included. The firing of a kiln of common clay generally results in a percentage of extra hard-burned, slightly undersize bricks, which, when necessary, may be bought for a premium covering the cost of selecting, usually about $1 per M. In determining the labor cost of laying brick, it is well to refer to the plans to ascertain if much cutting of brick be necessary. Gable end walls with sloping tops are bound to increase the labor unit. Corners, pilasters, reveals, etc., all retard the progress of a mason gang. As all masons in the squad should be ready simultaneously for the raising of the chalk line, the best bricklayers are usually placed at the corners. Especially when working from the interior side of the wall, there must be considerably more brick apportioned to the corner man than to those along the straight wall due to the space required by the mason to carry on his work. The construction of the building with regard to these features will greatly affect the unit labor cost allowed for bricklaying. A considerable variance in the cost of mixing mortar makes discussion of that branch of masonry estimating rather difficult. It has been the writer's experience that where one mixer can supply mortar for 5 masons, another under the same conditions may provide for 15. It may be required to find what part of the labor cost of brick laying is estimated for mixing mortar. A fair average would be to figure one day's wages for the mortar mixer as furnishing material for 7000 brick. 131⁄2 cu. ft. or 1⁄2 cu. yd. of sand is commonly estimated to provide mortar for laying 1000 brick, and may be used as the basis of material quantities. Should the specifications call for a 1-3 or 1-4 mix, the number of bushels of lime are determined by proportioning accordingly. As a bushel contains 1.2444 (14) cu. ft., the quantity of lime required is a simple computation. Again, if a cement gaged lime mortar is specified of 1-4-16 proportions, the basis of quantities is the 16 parts of sand. Let the 16 parts equal 1⁄2 cu. yd. and solve the other two volumes accordingly. Referring to the sample cost for 1000 brick, the proportion of the 134 bu. lime and 1⁄2 cu. yd. sand will be found to be approximately as 1-6, whereas, the mixture is designated 1-3. This difference is caused by the practice of estimating lime in the dry bulk state in which it is usually purchased. Slaking of lump lime nets about twice as much lime paste, which is the basis of the proportions. A wall of face brick is usually laid with colored mortar. The cost of the coloring per 1000 brick is added in the unit cost of the brickwork before extending. In the case of a wall combining face and common brick, where colored mortar is used only for the face brick, it is necessary to furnish the masons with two kinds of mortar. This is somewhat of a nuisance and necessitates a slight increase in the unit estimated labor cost. As is the case for practically all coloring pigments, the amount of mortar color depends upon the color and shade to be developed. For medium effective shades, an average of 40 lb. double strength, or 60 lb. single strength, is estimated for every 1000 brick. As far as the mortar is concerned, the coloring is a matter of material cost only. An increase should be made in the estimated unit cost for bricklaying when a light face brick is used with a dark mortar, or vice versa. These color combinations require care to be taken when distributing materials along the scaffold and also when building the wall so that there will be no discoloration of an expensive brick that is used ostensibly for the sake of appearance. The scaffold material item of $1 as it appears in the detailed estimated unit cost of 1000 brick is not intended to cover the cost for purchasing scaffold required to lay 1000 brick but covers the estimated deterioration of the contractor's equipment on hand. Due to the weight of materials, the mason requires a substantial scaffold. An accurate estimated cost of erection must be the result of experience in the class of work to be encountered. 12. Steel Sash and Operators.-The area of steel sash is listed in the estimate and the price per square foot is applied separately to each different class. An estimator familiar with market prices may be able to approximate a fairly accurate price per square foot for steel sash including glass and glazing complete, but as a rule it is advisable to take quotations from sash manufacturers particularly when large quantities are considered. Although sash are hardly ever sold by weight, it furnishes in conjunction with the number of joints a good criterion for the comparative price, as sash with small size lights weigh more than sash with large size lights, and the increased number of joints and ventilators increase the labor cost of production. The estimating of operators for steel sash is generally based on a unit of one lineal foot. There are many different makes of these operators on the market with a wide range of prices, like most specialties. For this reason the general contractor usually takes quotations to determine the amount to be allowed in the estimate. 13. Glazing Steel Sash.-Glass and putty are the two common materials included in the glazing estimate. The procedure for taking off and pricing common glass as well as other materials, must conform to the general methods of marketing. Glass is usually stored in cases, the sizes and number of pieces in a case being found on most any stock list. The areas of sheets of the same texture in standard lengths and widths up to 40 in. are listed in one group. Glass over 40 in. wide costs 10% more on the basis of area, and is therefore listed separately. When estimating odd sizes, the cost of the next larger standard size is taken plus 10 % for recutting. Ventilator glass is usually of special size as the lights at top and bottom of ventilators are in. shorter and the lights at sides of ventilators are in. narrower than the standard lights. Ventilator lights not touching at top, sides, or bottom of ventilator, are generally of same dimension as the main stationary lights. 4-in. wire ribbed glass costs about 30% more, and factory ribbed glass costs about 30 % less than double strength (D.S.) AA grade clear glass. Opaque glass as a rule is cheaper than clear glass as the imperfections cannot be as readily detected. Approximately 1 lb. of putty is required to glaze a 14 X 20-in. light. 1⁄2 lb. of putty is generally estimated for every square foot of standard side wall type sash, or 1 lb. for every 6 lin. ft. of stopping. The size of the openings in monitor sash varies greatly, and approximation of putty is hardly feasible from the basis of area. One pound will spread from 4 to 6 lin. ft. In all cases, the above values include both the puttying and back-puttying necessary to prevent the glass from bearing directly against the steel. Steel sash are usually estimated to be glazed after erection. Having no separate frames, sash are set when the wall is built. A large steel sash glazed before erection would be a delicate article to handle and more than likely most of the lights would be knocked out by the various tradesmen working on the upper part of the structure. The general estimated unit cost per square foot is often made up as follows: Before using the above unit costs, from 2 to 5% is added to the net estimated quantity of glass commensurate with the amount of shipping and handling. When glass is shipped by rail, material cost includes freight to site and labor cost is added for unloading. 14. Corrugated Iron or Steel.-Corrugated iron or steel is sold by the hundredweight. As estimated for steel buildings, however, it is conveniently taken in units of 100 sq. ft. The design drawings often show the size and position of each sheet, thereby simplifying the taking-off of quantities. The estimating of surfaces from drawings not showing the individual sheets may not be quite as accurate. The net area to be covered is listed in the take-off, plus an allowance of from 10 to 30% for side and end laps depending upon the surface slope with regard to weather. The standard corrugations are 2, 22, and 3 in. from peak to peak of each ridge. Common stock sizes are 271⁄2 in. wide and 5, 6, 7, 8, 9, and 10 ft. long. This width sheet covers a net strip 2 ft. wide, making a customary lap of 11⁄2 corrugations. The end laps range from 6 in. on a 14-in. pitch roof to 3 in. for vertical walls. A sheet of composition roofing is sometimes laid under the metal when covering roofs of less than 4 pitch. Corrugated covering may be fastened by steel clips bent around the supporting members, or by nailing to wood nailer strips. The gross number of squares of corrugated iron is extended at the unit price made up somewhat as follows: Material-1 sq. 24 ga. galv. standard 126 lb. at $8.20 per cwt... $10.33* The item of labor varies greatly with the height of the application and the surface with respect to number of openings. The price used would apply for favorable conditions—that is, to a low structure with a moderate number of windows. The labor would need to be doubled or trebled when estimating high surfaces broken by numerous doors and windows. 15. Carpentry.—Waste is a big factor in the estimating of lumber. Full size boards are rough, and dressing or planing will naturally reduce the covering values so that an extra percentage must be allowed. The increased quantities due to waste are included in the material take-off with the result that both material and labor costs are based on the gross amount of material estimated. When boards must be cut to odd lengths, there is another element of waste. The common standard mill lengths of lumber are from 10 to 30 ft.in multiples of 2 ft. Sticks 9 ft. long would be estimated as 18-ft. pieces cut in half. A stick 9 ft. 2 in. long may be cut from a mill length board of 10 ft. Long lengths of lumber cost more per thousand board feet than short lengths and must be so considered when determining nearest standard multiple of odd length required. Lengths of 10, 12, 14 and 16 ft., of like section, usually cost the same with an advance in unit price for each additional 2 ft. For instance, if the unit cost of 28-ft. lengths is 10% more than 16-ft. lengths, it is more economical to waste up to 10% more lumber in using the 16-ft. stock. Lumber should be so separated when listing in the take-off that pieces of different lengths and consequent varying costs can be priced separately. The table1 on p. 1040 should be of assistance in determining the number of boards required to cover the widths of various constructions that may be shown on plans. The lengths of the boards estimated as noted in the preceding paragraph must be considered with respect to the spacing of supports. The quantities of nails often estimated for various carpentry are: 1000 laths, 7 lb. 3 d. fine; or for 100 sq. yd. of lathing, use 10 lb. of 3d. fine. 1000 sq. ft. beveled siding, 18 lb. 6d. 1000 sq. ft. sheathing, 20 lb. 8d. or 25 lb. 10d. 1000 sq. ft. flooring, 30 lb. 8d. or 40 lb. 10d. 1000 sq. ft. studding, 15 lb. 10d. or 5 lb. 20d. 1000 sq. ft. 1 X 21-in. furring, 12 in. centers, 9 lb. 8d. or 14 lb. 10 d. 1 Originally compiled by J. J. Edwards. |