Part 10

Chapter 103,223 wordsPublic domain

=163. Plate Glass.=—The process of manufacturing =plate glass= is radically different from that of common sheet glass. The latter is blown, while the former is cast in large sheets and placed in annealing ovens to cool. When taken from the ovens the glass is rough and opaque, but it is afterwards ground and polished to make it transparent, the polishing being the most delicate process in its manufacture. Plate glass glistens like a mirror and reflects like one; objects seen through it are sharp and clean-cut; it has no imperfections or wavy effects, and does not distort and deform objects as does sheet glass.

=164. Beveled Plate Glass.=—The term =beveled plate= is applied to plate glass the edges of which are ground and polished to form a bevel, or border, around the glass. Plate glass finished in this manner is much used for glazing entrance doors and for ornamental work. The additional cost for beveling is slight compared with the effect resulting therefrom.

=165. Floor and Skylight Glass.=—=Floor glass= is made only from rough rolled or hammered glass in ½-, ¾-, and 1-inch thicknesses. The prices range from 30 cents to $1 per foot, according to the thickness.

=Skylight glass= is similar to floor glass, but can be procured in ⅛-, ³/₁₆-, ¼-, and ⅜-inch thicknesses, and in either ribbed or roughened surfaces. This glass is inexpensive, the prices ranging from 8 to 15 cents per square foot. Large quantities of skylight glass are used for mills, skylights, and various other purposes, but it is not used as a fire-retardant, as wire glass has entirely superseded it for this purpose.

=166. Wire Glass.=—Glass with wire embedded therein, as illustrated in Fig. 161, is made either ribbed, rough-rolled, “maze” design, or clear, polished plate. The wire netting is embedded in its center during the process of manufacture, thus producing a very strong glass that is a good fire-retardant. The temperature at which the wire is embedded in the molten glass insures cohesion between the metallic netting and the glass, and the two materials become as one; thus, if the glass is broken by shock, by intense heat, or from some other cause, it remains practically intact. Wire glass combines the strength of the wire netting and the glass plate, and the wire is so thoroughly covered as to obviate the possibility of rust or corrosion. This glass possesses extraordinary strength; a piece ¼ inch thick is as strong as ordinary glass of twice that thickness. When wire glass is broken, it will not scatter like plate or skylight glass; consequently, it finds extensive use for overhead work, where falling glass due to accidental breakage would be a source of danger.

Wire glass is made ¼, ⅜, and ½ inch thick, and up to 40 inches wide and 100 inches long. This glass is sold at from 30 to 40 cents per square foot for rough, ribbed, or maze pattern, according to the thickness, while polished wire glass costs either 60 cents, 95 cents, or $1.25 per square foot, according to the dimension of the light. Wire glass is practically burglar-proof and missile-proof, and when set in approved metallic frames forms a most efficient fire-retardant window. In its use as a fire-stop, it possesses advantage in that it does not hide the incipient blaze like steel-plate or tin-lined shutters. Windows glazed with wire glass require no shutters for protection, but an opening may be made in it by a blow from a fire-ax. Wire glass as a fire-retardant is approved by the various boards of fire underwriters, and it may be used for windows, skylights, and other exterior openings exposed to fire hazard.

=167. Prisms, or Prismatic Glass.=—When a ray of light passes from air to glass, it undergoes the change in direction called _refraction_. The knowledge of this property of light is utilized in the design of =prismatic glass=, an example of which is illustrated in Fig. 162. Prisms are made of clear crystal glass, with the outer side usually plain. The inner side, however, is formed into prisms of a great variety of angles made to suit the several conditions under which the lights may be used. Prism plates are made in two styles: _Pressed prism plates_, which are composed of 4- or 5-inch pressed lenses that are glazed together with a drawn zinc or copper bar, the several bars forming a frame being brazed together electrically, and _rolled_, or _sheet, prisms_, which are first rolled in large sheets and then cut to size.

Under average conditions, the direct light from the sky entering a room through sheet or plate glass strikes the floor within a few feet of the window and is mostly absorbed. For this reason, the rear part of the room is dark. By the installation of prisms at the window openings, however, the direction of the entering light is changed and projected horizontally into the room. Prisms do not create light; they simply distribute and diffuse the excess light at the window. Under certain conditions the effective light in a room may be increased fifty times by the installation of prisms. In Fig. 163, the arrows _a_ show the direction of the lowest rays from the sky over the cornice of the opposite building, striking the prism plate at the floors. These arrows also indicate vertical rays, striking canopies and skylights, while the arrows _b_ show the directions of the rays just mentioned after passing through the prism plate; also, the manner in which the light rays are projected into the building.

=168. Vault Lights for Basement, or Cellar, Lighting.=—Where the sidewalk and the basement ceiling are nearly on a level, basement rooms can be successfully lighted by the installation of =vault lights=, or _glass pavement tile_. The ordinary method is to use plain, round, or square lenses, which are set in iron or concrete in iron frames, as illustrated in Figs. 164 and 165, though vault lights are now made with the supporting material of reinforced concrete. Where the ceiling is low or the room at all deep, the system in which plain lenses are used is unsatisfactory, as the direct light from the sky in passing through the lens strikes the floor immediately underneath.

The more modern method is to use prism tile set in the necessary frames. The prism receives the direct light from the sky on the upper face and turns, or refracts, it back into the basement, as illustrated in Fig. 166. Where the head-beam or other obstructions interfere with the deflection of light direct from the prism, it becomes necessary to use in connection with the skylight or canopy just described an independent vertical frame of window prisms of varying angles. These prisms intercept the light from the pavement tiles and project it into the basement, thus utilizing the light to the maximum advantage.

=169. Glazier’s Points.=—A necessary adjunct in glazing with putty is the sheet-zinc, triangular =glazier’s points=, as illustrated in Fig. 167. These points are made in six sizes, which range from No. 000, the largest, to No. 3, the smallest. They are also made in somewhat similar shape, called _sharps_, but this type is not so popular as the _triangle point_.

=170. Grades of Putty.=—Putty is usually graded as follows: _Commercial_, a very cheap grade; _pure_, a medium grade; and _strictly pure_, the best grade, which is made of pure whiting ground in linseed oil. The cheaper grades are made in the same manner, but with an amount of adulteration, either in oils or whiting, commensurate with the cost. Therefore, the cheaper the putty, the more it is adulterated, and none but strictly pure should be used when good results are desired.

_White-lead putty_ is in a class by itself, and costs about twice as much as strictly pure whiting putty; but where permanent glazing is required, its use will show handsome returns on the investment.

ESTIMATING AND CALCULATING QUANTITIES

(PART 1)

INTRODUCTION

=1. Scope of Subject.=—The art of estimating is very important both to the architect and to the builder; to the latter, in that he must employ some systematic method of estimating in order to carry on his business successfully, and to the former for the reason that he should at all times be able to estimate the cost of the buildings that he designs.

The science—for such it is—of fixing prices on a piece of work in any branch of the building trades must be based on an extended experience. With a little practice, any one can learn to take off the quantities of materials, but when it comes to determining the rates, only persons having extensive and varied knowledge of building and costs of various details can accurately estimate the time and labor required to complete the work. In order, then, that the duties and requirements of a practical estimator may be thoroughly understood, a number of detailed estimates will be given in this Section as guides. It should be remembered, however, that as the prices of materials and labor vary from those assumed, so will the estimates vary. The information given in detail should be considered only as a general guide in analyzing the elements that enter into the constructive problems in each department of the building trades. In this way it will be possible to determine intelligently the various unit costs. The estimates given are, in general, net figures, and do not include any contractor’s profit.

=2. Qualifications of the Estimator.=—In the United States, there are no standard or definite rules on estimating that hold good in every section. The builders of each locality have their own ideas and customs regarding the subject. This fact, together with the difference in the cost of labor in various parts of the country and the fluctuations in the market price of materials, requires, as before remarked, that a competent estimator be a man of long and varied experience in the business. There are, however, certain practical rules and suggestions that will materially assist in taking off the quantities and in valuing the labor required for any building operation. These points will therefore be taken up and considered in detail in this Section.

=3. Important Factors.=—The prime considerations in making an estimate are accuracy and time. To these ends the estimator must systematize his efforts, and endeavor to do a maximum amount of work in a minimum amount of time. This, however, should not be done at the expense of accuracy, for accuracy is the most important factor and is only insured when the figures are carefully checked. The estimator, therefore, while avoiding too great refinements in calculation, should aim at correctness rather than at speed in doing the work. Very frequently do the effects of haste and inaccuracy in estimating the cost of a structure become evident when it is too late to remedy the errors, resulting sometimes in the financial ruin of the builder that trusts too implicitly in the estimator’s figures.

A record should be kept of all estimates made, as this kind of information is most valuable and establishes a precedent on which to base subsequent estimates, as well as a check on the work at hand.

PRINCIPLES OF ESTIMATING

APPROXIMATE ESTIMATING

=4.= In order to make a preliminary estimate, before the plans of a structure are drawn, but after the general dimensions of the proposed building have been determined, architects and builders sometimes employ a method of =approximate estimating=, by which the cost is figured at so much per cubic foot of the building, the rate varying according to its character and the finish required. The method is also considerably used by insurance companies in fixing the amount to be placed on a building. It should be borne in mind that this method gives the approximate cost only, and should never be used in figuring the contract price of a building. This estimate, however, may be used to advantage in checking the accurate estimate, with which it will frequently be found to agree remarkably well.

TABLE I

COST OF BUILDINGS PER CUBIC FOOT

Table I shows the approximate cost per cubic foot of various kinds of structures. In computing the contents of a building, there is no uniformity in practice, but no great error will be made in figuring the solid contents from floor of cellar to ridge of roof.

OUTLINE OF THE WORK

=5.= The drawings and specifications of a structure are the guides that the estimator must follow in making his computations. All measurements necessary for calculating the quantity of the materials required are obtained from the drawings; and all information in regard to the character of the workmanship and the quality of the materials to be used is furnished by the specifications.

In compiling a schedule, there are three stages to the operation: (1) Taking the dimensions for each of the various classes of work; (2) computing and collecting the quantities; and (3) estimating the cost.

In carrying out the first of these steps, each of its subdivisions should be considered in the order in which the work will be executed in the building. This order is about as follows:

1. Excavation 8. Joinery 2. Concrete work 9. Hardware and ironwork 3. Stonework 10. Heating and ventilation 4. Brickwork 11. Plumbing and gas-fitting 5. Carpentry 12. Painting and papering 6. Roofing 13. Glazing 7. Plastering

The third step, estimating the cost, may be subdivided into cost of labor and cost of material. The latter can be definitely fixed by an examination of lists giving current prices of materials; while the former must be based on a fixed rate of wages per day for the various classes of workmen.

The second and third branches of the work, being closely connected with the first, will be partly considered in connection with it, and, later, in detail in the complete example on estimating.

ACCURATE ESTIMATING SCHEDULE

=6.= There are so many items to be considered in a careful estimate, that the estimator should have a list of those coming under each of the main headings already given, and in compiling a schedule he should follow this order. The following list, which is arranged to assist in making an estimate on a dwelling house, will serve as an example of the general method that should be adopted:

EXCAVATION

Cellar Wells Areas Pipe trenches Piers Fence trenches Privy vaults Grading Footings Filling Cesspool Labor Catch basins

CONCRETE WORK

Cement Wells Sand Area walls Broken stone Chimneys Form lumber Footings Foundation walls Floors Partition walls Columns Piers Pavements Exterior walls Fences Concrete blocks Hearths Concrete cornices Steel reinforcement Core walls Anchor bolts Backing Nails and spikes Cesspools Labor Tanks

STONEWORK

Lime Wells Cement Chimneys Sand Footings Mortar Cut or dressed stonework Foundation walls Carved stonework Exterior walls Pavements Partition walls Stone fences Piers Stone hearths Area walls Anchors and bolts Cesspools Labor

BRICKWORK

Lime Cesspools Cement Wells Sand Range setting Mortar Furnace setting Foundation walls Footings Exterior walls Chimneys Partition walls Trimmer arches Piers Brick hearths Area walls Pavements Terra-cotta work Fences Tiling Labor

CARPENTRY

FRAMING

Girders in cellar Joists, first story Sills Joists, second story Cross-sills Joists, third story Posts Joists, attic story Beams Ceiling beams Girts Headers Studs Trimmers Plates Common rafters Deck plates Hip rafters Tower plates Valley rafters Braces Purlins Joists, basement Furring Ridge pole Carrying beams Collar beams Ironwork Lintels Rods and bolts Framing piers Nails and spikes Outlookers Labor

COVERING

Sheathing lumber Flooring Sheathing paper Corner boards Base Casings Siding Cornice Shingles Labor

ROOFING

Tin Gutter linings Shingle Solder Slate Cresting Tile Finials Paper or felt Conductor hooks and fastenings, Hanging gutters nails and hooks Conductor pipes Cast shoes or boots Conductor heads Labor Flashings

PLASTERING

Lath Three-coat work Lime Plaster board Sand Patent plaster Hair Tiling, marble, etc. Plaster of Paris Stucco cornices Plastering mortar Stucco arches Deafening Stucco centers Back plastering Nails One-coat work Labor Two-coat work

JOINERY

INSIDE AND OUTSIDE FINISH

Window frames Doors Door frames Base Sashes Architraves Corner and plinth blocks Posts Outside and inside blinds Columns Brackets Balusters Wainscoting Hand railing Moldings Nails and screws Planed lumber Labor

STAIRS

Rough lumber Hand railing Treads and risers Balusters Strings Brackets Spandrels Bolts Moldings Nails and screws Newels Labor

HARDWARE

Mortise locks Sash lifts Rim locks Sash cord Padlocks Transom lifters Butts (various sizes) Cupboard catches Wrought butts Hooks and eyes Strap hinges Drawer pulls Blind hinges Mortise bolts Sash fasteners Door stops Sash weights Door hangers Shutter bars Axle pulleys

HEATING AND VENTILATING SYSTEM

HOT-AIR HEATING

Furnace Registers Cold-air ducts and slide Sheet-tin and asbestos dampers fire protection Hot-air pipes, elbows, and dampers Smoke pipe Register boxes Labor

STEAM HEATING

Boiler Smoke pipe Regulating and safety Steam pipes appliances Return pipes Fittings Galvanized sheet-iron casings Hangers for indirect stacks Indirect, direct-indirect, Sheet-iron indirect flues, screens, and direct radiators and dampers Valves Indirect registers and boxes Air vents Japanning and bronzing Floor and ceiling plates Pipe coverings Labor

HOT-WATER HEATING

Heater Automatic damper regulator Smoke pipe Expansion tanks Radiators, pipes, fittings, etc., same as for steam heating Labor

PLUMBING AND GAS-FITTING

PLUMBING FIXTURES

Kitchen range with water-back Kitchen sinks Plunge baths Pantry sinks Shower baths Slop sinks Foot baths Laundry tubs Sitz baths Safes Wash basins Hot- and cold-water faucets Water closets for fixtures Urinals Labor

WATER SUPPLY

_City Supply_ Pumps Permits Supply tanks Corporation connections Outside piping Excavation Lawn and garden hydrants Extra-heavy lead, iron or Fittings, etc. brass service pipe Wrought-iron pipe fittings Curb cock and box Brass pipe fittings Stop and waste Lead pipe fittings

_Well Supply_ Solder nipples Storage cisterns Stop-cocks Cistern filters Pipe straps Metal tacks Wiping solder Kitchen boiler and stand Labor

HOUSE DRAINAGE

Permits Lead soil, waste, Sewer connections and vent pipes Excavations Lead traps Vitrified sewer pipe Brass traps and fittings Fixture connections (brass) Earthenware traps Wrought-iron, galvanized, or Portland cement asphalt-coated drain, soil, Unglazed drain pipe and vent pipes and fittings Cast-iron soil pipe and Fresh-air inlets, vent caps fittings Vent-pipe flashings Lead and oakum Wall hooks, straps, bands, Cast-iron traps and hangers Handholes and cleanouts Wiping solder Lead bends, brass ferrules Labor

GAS-FITTING

Permit Chandeliers Tapping main Pendants Excavation Wall brackets Meters Pillar lights Stop-cocks Globes, shades, and fireguards Drip cups Gas stoves and ranges Piping Gas-heater connections Straps and hangers Labor Fittings Pressure regulators

PAINTING AND PAPERING

PAINTING

Body of house Floors Trimmings Ceilings Blinds Walls Roof Sash Porches Shelving Inside work Mantels Oiling Fences Polishing Outbuildings Varnishing Labor

PAPERING

Paper Lining paper Borders Labor

GLAZING

Sheet glass Ribbed glass (single or double thick) Frosted glass Plate glass Glaziers’ points Leaded glass Putty (stained or clear) Labor

EXCAVATION

=7. Excavation= is generally measured by the cubic yard, although, in a few localities, measurement by the perch is still in use. If the latter method is adopted, it should be stated just what is meant by a perch, as this varies considerably in different parts of the country.