CHAPTER VIIEstimating
74. Methods of Estimating.—Building costs may be divided into two main divisions, cost of material and cost of labor. There is but one so-called safe way to figure or estimate the cost of any particular piece of carpentry work. This consists in "taking off" the material quantities in detail and to this adding the labor cost of placing the same. This is the method in common use by contractors in making a final estimate. Where a rough or working estimate is required, such as an architect's estimate of the probable cost of a building planned by him, two methods may be used. One consists in figuring the cubical contents in feet and multiplying a predetermined, or unit price per cubic foot for that type of house. Ordinarily, the main frame is figured, counting from the basement floor to the top of the attic walls that are, or may be finished—outside measurements. Porches and open spaces are not figured. A second method consists in estimating the number of squares (100 sq. ft.) of side wall, of partitions, of floors, etc., and multiplying a predetermined price per square for a similar type of building. This latter method is more accurate than the cubic-foot unit method.
75. Table for Estimating by Cubic-Foot Unit.—The following table of unit prices will give a rough working estimate for various types of building differentiated after the custom of insurance adjusters. The prices are for 1915 and to be of any value must be compared with known costs of similar structures in the community in which they are to be used. Any evident variations in unit costs so discovered should be noted and corrections made.
76. Grading Rules.—There is no uniformity as to grades of lumber. Fifteen or more associations have rules for inspection. and classification of lumber and these rules vary with the association and from year to year in the same association. The following rules taken from a catalogue of a middle west lumber concern will be found helpful:
Yellow Pine Dimension, Studding, Joists and Timbers
No. 1 Common.—The best grade and the one recommended for use on first class jobs.
No. 2 Common.—Dimension up to 20 feet long only can be obtained in this grade. Timbers are not manufactured in No. 2. This stock will show defects not found in No. 1 grade, and some pieces are not entirely straight. It is a sound, serviceable grade, but not recommended for first class work.
Yellow Pine Boards, Sheathing, Shiplap, and Fencing
No. 1 Common.—This grade is not clear, but is strictly sound and uniform in thickness and width. It is used on the best classes of work, for barn boards, and wherever exposed to wear and weather.
No. 2 Common.—This grade is sound but contains more sound knots than No. 1 and is somewhat coarser. It is mostly used on first class jobs for sub or rough floors, and for sheathing under siding. It can be used for outside work, but is not recommended for this purpose except upon cheap buildings. No. 8 Common. A fairly good lower grade which will work up nicely but with some waste due to cutting out defects. Runs uneven in quality. Makes a fair subfloor or sheathing.
Yellow Pine Flooring, Ceiling, Partition, and Drop Siding
Clear Grade.—The best grade manufactured. Practically free from defects and the grade used upon first class jobs. Is strong, sound, and will lay without waste due to cutting out of imperfections. Should be used when a natural finish is desired. No. 1 Common. This grade will contain small, sound knots, sap stains, pitch or pitch pockets. It is sound and durable, and a good grade for ordinary work or wherever covered with paint.
No. 2 Common.Coarser than No. 1 grade; will lay up with little waste. Is sound, and flooring of this grade is often used for sheathing or sub flooring where a warm, tight job is desired. Can also be used on cheap painted jobs.
Fir Boards, Timbers, Drop Siding, Ceiling and Flooring
Select No. 1 Barn Boards.—This grade is especially selected and is better than No. 1.
No. 1 Timbers.—Good sound straight stock, to be used for sills and posts subjected to moisture.
Clear Ceiling.—Free from defects. Good for cornice work and porch ceilings.
Edge Grain Flooring, Clear Grade.—Especially suited to porch floors as it wears well and resists effects of moisture.
Clear Drop Siding.—Contains no sap, shakes or other defects.
Shingles, Lap Siding, Y. P. and Cypress Finish, White Pine Boards
5 to 2 Clears.—The heaviest grade five shingles laid one on top of the other will measure 2" at the butts.
6 to 2 Extra Star A Star.—A lighter grade, but clear and 16", as are the 5 to 2" grade.
Bevel or Lap Siding.—Carried in stock in red cedar, redwood, cypress, and white pine. "Clear" is free from all defects.
Cypress "C" Grade.—Has small sound knots and other slight defects such as can be covered with paint. All siding is bundled 10 pieces to the bunch in random lengths. Not furnished in specified lengths.
Yellow Pine and Cypress Finish.—This stock in "clear" grade is practically free from defects. The yellow pine is suitable for interior finish. Cypress is suitable for inside finish or for cornice work on first class jobs. "C" cypress finish contains some knots and other slight defects. Is suitable for outside finish on ordinary jobs.
White Pine Boards.As a rule, carried in stock only in No. 1 grade. Nothing but sound, red-knotted boards should be included. No shakes. Excellent for exposure to weather.
77. Estimating Lumber Quantities.—Lumber is measured in terms of the board foot as a unit, 12" by 12" by 1" or its equivalent, indicated by the abbreviation B. M. (board measure).
Example:Determine the B. M. in a girder 6" by 8" by 16'.Solution:Rule—Thickness in inches times width in inches, divided by 12" timesthe length in feet gives a number equal to the number of board feet.(6" × 8") / 12 × 16' = 64' B.M.
Stock less than 1" thick is figured as 1" thick. In commercial practice lumbermen make use of tables in determining quantities. Appendix III.
In estimating quantities, suitable allowance must be made for waste. This waste is incurred (1) thru loss when boards or planks are cut to required lengths. Standard lengths are 10', 12', 14', etc., and these will not always cut to advantage. (2) Waste is incurred in machining the stock, as dressing, edging, tonguing and grooving. Necessary allowances will be indicated herein.
Heavy Timbers.Girders, posts, etc., are determined by count.
Joists.To determine the number of joists required for a room or a building, count the actual number required beginning at a wall (¾ times number of feet in length or width of room when set 16" on centers), and to this add one joist to be placed against the second wall.
Cataloged or listed sizes are for lumber fresh from the saw. Shrinkage due to seasoning and surfacing one side and one edge so that the stock may have uniform thickness and width will give actual sizes as follows: 2" × 4" when sized on one side and one edge, will give 1⅝" x 3⅝"; 2" × 6",S-1-Sand 1E, 1⅝" × 5⅝"; 2" × 8",S-1-Sand 1Egives 1⅝" × 7½"; 2" × 10",S-1-Sand 1Egives 1⅝" x 9½"; 2" x 12",S-1-Sand 1Egives 1⅝ x 11½. WhenS-2-Sand 2Eor sized on 4 sides, stock will measure ⅛" less than indicated above.
Studs for Walls and Partitions.—Count one for each lineal foot of wall or partition, where specified 16" on centers. The extra studs are to be used in doubling corners, at doors and windows, and in gables. Barns and sheds will not require these extra studs.
Bridging.—Allow 25 lineal feet of 2" by 4" for each square of flooring.
Rafters.—On a plain roof, count actual number and add one, as in counting for joists.
Sheathing.—Calculate the exact surface to be covered, deduct openings; then, for unmatched sheathing or barn boards or fencing, as it is also called, add 1/12 for 12" boards, 1/16 for 10" boards and ⅛ where 8" boards are used. Four inch and 6" are seldom laid solid, being used mainly for roof sheathing for shingle roofs, and laid 2" apart. These additions are due to the fact that thru seasoning and dressing, a 12" board becomes 11½", a 10" becomes 9⅝", an 8" becomes 7¾", a 6" becomes 5¾" and a 4" becomes 3¾". The additions specified allow for waste in cutting.
Shiplap.Calculate the exact surface to be covered, deduct openings; then add for floors 17%, for sidewalls 20%, for roofs 25%.
Sheathing laid with 2" spaces should have proportionate deductions made, that is, on 1" × 6", figure as if laid solid, then deduct ¼; for 1" × 4" deduct ⅓. Sheathing when matched, such as is used sometimes for sub-floors and side walls and roof sheathing under slate roofs and better known as flooring, will be estimated by figuring the exact surface to be covered, deducting the openings, then adding for 6" stock, which is the kind most always used, 15% for floors, 17% for sidewalls, and 20% for roofs.
If shiplap or matched sheathing is laid diagonally add 5% for waste due to lack of ability to reverse cut.
Siding.— For bevel siding, calculate the exact surface, deduct openings; then add for 6" siding when laid 4½" to the weather, 33%; for the 4" siding add 50%.
Drop Siding.—Drop siding, ceiling and wainscoting are figured just like matched flooring, which is described below.
Flooring.—For square edge, calculate the exact surface to be covered, add for 6" flooring 11% for waste in matching, etc.; for 4" flooring add 20%. It is becoming common practice to specify flooring by actual face measurement after being machined. The following figures are for actual surface measurements.
For matched flooring, calculate the exact surface to be covered, then add 20% for 5¼" flooring, for 3¼" flooring add 25%, for 2¼" add 33%, for 1½ add 40%.
Flooring less than 1" thick, like all other lumber, is estimated as 1" thick.
Shingles.—A bunch of shingles contains the equivalent of 250 shingles of 4" average width. With an exposure of 4½" to the weather a 4" average shingle will cover 18 square inches, making 800 shingles to the square. Waste in doubling the first course and in laying will necessitate an addition of 8% on a plain roof and 12% on hips or on gabled walls. Cost estimates are based upon the M. or 1000.
SHINGLES PER SQUARE
Plain roof, 4 " exposure, 990; roof cut up, 1010Plain roof, 4½" exposure, 880; roof cut up, 900Plain roof, 5 " exposure, 790; roof cut up, 810
Lath.Lath for interior plaster work are usually ⅜" by 1⅜" by 4', put up in bundles of 50 each and are sold by the 1000. 1000 lath will cover 70 yards of surface and will require 8 lbs. of 3d fine lath nails. Lathing is usually considered a part of the plasterer's contract. There is no uniformity of practice as to the deduction for openings.
Building Papers.The cheapest is "rosin sized," and is not waterproof. This is used mainly under floors and upon side walls under bevel siding. It is sold by the pound in rolls each 36" wide containing 500 square feet.
Dry felt is used where better protection from cold is desired. In the cheaper grades, the material is made of wood fiber and rosin. In the better grades wool is used. Tar felt, used where moisture is to be resisted, is dry felt saturated with tar. These materials are sold by the pound: 12, 15, and 20 lbs. to the 100 square feet, in rolls of various widths. A catalog should be consulted for weights and covering capacity.
78. Estimating Millwork Quantities.—The number of doors and windows will be determined by an actual count.
Mouldings, casings, baseboard when moulded, window stools, etc., are sold by the 100 feet lineal measure, random lengths. Extra charge is made for specified lengths where the quantities are determined by scale measurements of the plan and elevations. Window frames of stock sizes, door frames, inside jambs, stair parts, buffets, etc., will be found priced in millmen's catalogs, and assist greatly in determining prices for ordinary work. This text cannot give space to list such data, which is so readily obtained from commercial catalogs.
79. Example of Form for Bill of Materials.—
80. Estimating Labor Costs.[A]—In estimating labor costs the following data is to be made use of. The estimator will have to determine the hours per day and the scale of wages per hour paid in his locality, and make whatever changes in the data is necessary. He should also compare the quantity of work done by men he may observe with that given herewith. The time data herewith is based upon the work of one mechanic who has mastered his trade fairly well. With an efficient foreman and a selected group of workmen these time allowances can be reduced in many instances as much as one-half. Experience alone will determine the possibilities of such reductions with safety.
[A]For a more complete treatise of labor costs, the student is referred to Gillette's Handbook of Cost Data, Section X, the source, in the main, of the basis of this data.
[A]For a more complete treatise of labor costs, the student is referred to Gillette's Handbook of Cost Data, Section X, the source, in the main, of the basis of this data.
COST OF PLACING FRAME AND COVERING
By One Man
COST OF PLACING FLOORS
By One Man
COST OF BRIDGING AND FURRING
COST OF PLACING BASEBOARDS
COST OF PLACING DOORS, WINDOWS, BLINDS
ESTIMATING
COST OF STAIR WORK
PORCHES IN GENERAL
LATH
MISCELLANEOUS LABOR ITEMS
81. Estimating Quantities of Nails.—The following table will enable one to estimate the quantity of nails required for the various kinds of common carpentry. The table of length and number of nails to the pound, Appendix III, may be made use of in determining nail estimates for other kinds of work not here specified.
QUANTITIES OF NAILS
82. Example of Form for Carpentry Costs.—The following form, used by a practical carpenter, and published in the Correspondence Department ofThe American Carpenter and Builder, should suggest means whereby the data just given may be made more readily available for estimating purposes.
It must be remembered in interpreting all such data that costs will vary greatly with conditions. A carpenter, for illustration, who gives his time and attention to general carpentry cannot lay shingles with the speed a specialist in shingling can. Again, a carpenter cannot make window and door frames by hand with the same speed that these can be made by machinery in a mill. The prices given herewith are for work done by a general carpentry mechanic. The estimator should test out these figures to see how they compare with actual working conditions in his community. The following table is made for "country" conditions, the men working at 30c per hour, 9 hours a day.
MATERIALS IN PLACE AT 30c PER HOUR
M = 1000 Ft. L = Lineal Sq = Square Feet.
Shingles are for new roofs; where hips and valleys are required add 5% additional for each one; where old shingles and nails must be removed, add again (20% to total) for this work.
The above rate is based on figures of 30c per hour. For other rates the following will apply in addition: At 35c per hour add 17%; at 40c add 34%; at 45c add 51%; and at 50c per hour add
Example:(A) Take 1,000 feet of hardwood floor to be cleaned at 50c per hour =$54.00 + $36.72 = $90.72Looking again we find it would take 180 hours at 50c per hour = $90.00
(B) Take 1,000 feet of joists to be placed at 50c per hour = $6.00 +14.08 = $10.08.Looking for the hours we find it would take 20 at 50c, or $10.00.
83. Total Building Costs by Percentages.—Having carefully estimated the costs of one or two of the large items in a building, such as lumber or millwork or labor, the total cost of a building may be approximated with a fair degree of accuracy by a general contractor by means of the following table of percentages. Foundations or any other parts of a building which may be unusual should be excluded and figured separately in detail. In any event, before a building is finally completed the contractor will have to settle with each sub-contractor upon the basis of detailed cost estimates. Where time is available, the contractor as a rule secures bids from the various sub-contractors, such as the plumber, the lather, the mason, etc., combining these and adding his commission of 10% for oversight, and an additional 10% for incidentals or contingencies.
COSTS BY PERCENTAGES
Example:A lumber bill for a given frame house is found to "figure" $500,determine the approximate cost of the various sub-contracts, andfor the house as a whole.Solution:$500 = 19% of the total cost.Total cost = $2632 (exclusive of heating).Excavation, brick and cement work = 16% of $2632= $421.12Plastering = 8% of $2632= 210.56Millwork and glazing = 21% of $2632= 552.72Carpentry labor = 18% of $2632= 473.76Hardware = 3½% of $2632= 92.12Tinwork = 2½% of $2632= 65.80Plumbing = 7% of $2632= 184.24Painting = 5% of $2632= 131.60Lumber= 500.00$2631.92
To this must be added heating, electric wiring, electric and gas fixtures, window shades, cement walks, sewerage, grading, decoration of walls, architect's fee and contractor's commission.
For furnace heat, add 6 to 7% ; for steam, add 8 to 10% ; for hot water, add 10 to 12% additional.
For electric wiring, add 1¼%. For fixtures, electric and gas, add 2 to 3%.
To this total add 10% for incidentals and contingencies; add 10% for contractor's charge. Above this amount add 6% for architect's fee, to get the cost to the owner.
Such a method of estimating should not be mistaken for anything but fairly safe approximation where normal conditions exist.