CONSTRUCTION IN WOOD

BY HENRY D. DEWELL

Many of the features of the contractor's plant for the construction of a timber-framed building will be the same as for the erection of a building with steel or reinforced concrete frame. For example, it should be obvious that in all construction jobs there should be an orderly arrangement of plant with proper facilities for receiving, checking, and storing material, also for delivering the material from the general storage yard to the various points of fabrication. The detail method for accomplishing this work will depend largely upon the size and character of the building. Further, it is hardly necessary to state that some simple method should be put in force for keeping the cost of the various parts of the work. These remarks may appear to be commonplace. Unfortunately, there is a tendency, when dealing in timber construction, to be careless in both arrangement and character of work.

49. Storage of Material.—In the case of a concrete building, since the lumber for forms is only used temporarily, no particular provision for preventing incipient decay or rot need ordinarily be taken. On the other hand, for permanent timber construction, all lumber when received on the job, should be immediately protected from the weather and also from contact with the ground. Timber when in contact with the ground may soon become infected, with the result that disease will start and may continue after incorporation of the timber with the building, if conditions are favorable to growth of fungi.

All lumber should be segregated into the various sizes and lengths, and carefully piled on firm level foundations with supports at intervals not exceeding 4 ft. If unseasoned, the lumber should be "stuck," i.e., the pieces in any one layer separated by a 1- or 2-in. air space, and each layer separated from the upper and lower layers by means of 1-in. cleats. In "sticking," care must be exercised to see that the "sticks" or cleats are placed directly over the foundation sills throughout the pile; otherwise, the timbers will be warped. Finally, a temporary roof should be constructed over each pile, the roof projecting a foot or two over the sides and ends of the pile. The best lumber can easily be ruined by careless piling and exposure to sun and rain, and any warping results in increased cost of framing.

All iron work, such as truss rods, castings, washers, plates, etc., should be arranged in neat piles and plainly labelled. Bolts should be segregated into the various diameters and lengths and placed in a bolt rack, with each size and length numbered.

50. Working Details.-Working or field details should be provided for all timber construction. This statement applies particularly to those buildings involving roof truss construction. Very few plans for timber-framed buildings give full and sufficient details of all connections. This practice results, in part at least, from the common procedure in the preparation of plans for steel-framed buildings, where the designer prepares only "contract plans" and relies upon the contractor to furnish "shop details" for approval. When such a designer has a timberframed building, he works along the same lines, preparing, as usual, the "contract plans," and the "shop details," if any, are comprised in the contractor's drawings of the incidental steel work.

Time and money will be saved in all timber-framed construction, except the very smallest and simplest, if full working details are prepared. These details should include an erection plan, details of all joints, cutting lengths of all timbers, details of all metal work, lengths and diameters of rods and bolts, etc. Letters and numbers should be placed on the plans for all members, and a complete detailed list of materials made with the letters and numbers repeated from the plans. The different materials in the storage yard should then be designated with the same markings, so that a workman can instantly find any piece of material shown on the plans.

51. Methods of Construction.-Two methods of construction may be mentioned: (1) fabricating all material before erection is started, and (2) erecting material as fast as it is fabricated. The second method is preferable as it enables the contractor to realize on his work at the earliest possible moment.

In any event, the first floor should be constructed as soon as possible, with the rough floor in place, in order that all trusses, posts, etc. may be laid out and fabricated on the floor. A smooth, level floor is preferable for such purpose to any fabricating platform that can be. constructed.

The center lines or outside lines of trusses should be laid out on the floor to actual sizes. Sometime templates of all timber members are constructed and the actual members cut directly from these patterns. In other cases, no templates are made, but the members are cut from the figured dimensions or the dimensions scaled from the full size layout. The template method is to be recommended. It may seem an unnecessary expense, but will avoid many mistakes of cutting members too short, cutting daps at the wrong places, etc.

In laying out a truss, the outside lines of timbers should be used as working lines, and all dimensions figured from them. For example, given a lower truss chord 12 in. deep, with diagonals framing into the upper side to various depths, as 34 in., 1 in., etc. Instead of measuring such cuts from the upper side, the measurements should be made from the lower side. This will take care of all variations in width of the timber chord and will enable all similar diagonals to be cut to the same length.

52. Camber in Trusses.-Most specifications for timber trusses call for camber to be given to the trusses. This camber is usually specified in terms of camber per linear foot of truss, as 1⁄2 in. for every 10 ft. of span. Camber in ordinary roof trusses is usually introduced by springing the chords on the fabricating platform to approximate arcs of circles and cutting the diagonals to fit. In other instances, especially in small trusses, the trusses are framed with straight chords, and joints left somewhat loose, and the whole truss then given an approximate camber by tightening the rods. Such a method, it is obvious, does not give a real camber to the truss, and if the truss, after erection, retains any of this so-called camber, it is due solely to the restraining action of the posts or walls. If true camber is to be introduced in a truss, the members must be cut accordingly, and all joints made tight before erection of the truss.

53. Equipment. The question of amount of machinery and tools can only be determined by the character and size of the job. In general, it will always pay to provide sufficient tools, and power machinery will save much labor. However, more than one job has been a loss on account of too great an investment in plant.

When there is much boring to be done, power drills should be installed. These are of two kinds, electric and air drills. Of the two, the latter are the more satisfactory, but in many jobs the contractor will hesitate to install the necessary air-compressor plant. Electric drills are preferable to hand boring, but are heavy and somewhat cumbersome. Many of them operate on but one speed and do not reverse. With such drills, difficulty will be experienced in driving long holes, since the drill will tend to stick, and the drill must be constantly and expertly fed into the hole.

A small cross-cut and ripping saw may well be installed on jobs of some size, especially where there is much duplication of typical members.

54. Erection. Hand power is the most expensive that can be used for erection. In buildings involving truss work, some form of traveller or derrick should be installed, even if only operated by a hand winch. It is hardly necessary to state that the work should be so arranged that once erection has started it can be carried on continuously. All fabrication of members should be done as completely as is possible on the ground, leaving the least amount of work to be done after hoisting.

STONE WORK

By A. G. MOULTON

The term masonry as referred to building construction, generally implies stone or brick work only, and is quite distinctive from cement work, fireproofing, plaster, or marble, each of which is treated under separate specifications despite their requirement of the trowel as a common tool.

55. Use of Building Stones and Stone Masonry.-The use of stone masonry for foundation walls and piers below grade is now seldom met with, the more economical material-concretehaving displaced it with the rapid building up of our cement industry. Above-grade stone is now used largely for ornamental purposes. Beginning with the field stones and boulders used in garden wall and residence work, and carrying through to the higher ornamental and carved marble employed in our more ornamental buildings, all kinds of quality of stone masonry will be encountered by the builder. The limestones, sandstones, and granites, however, are those most commonly used for exterior facings.

In localities convenient to the quarries, it is not uncommon in wall bearing structures to run up the entire thickness of the wall in stone, bedding furring strips at proper intervals for cross-furring and lath to be applied later on the inside face. If the stone is not a local product and freight enters into the cost, then it is more usual to reduce its thickness to that minimum required for its use as a veneer, and to bring up the wall to its full structural strength and thickness by a backing of brick work or other product of the kiln. For use on skeleton constructed buildings. where minimum construction weights are such a determining factor, its use as a veneer is the only one practicable,

56. Preventing Stains on Stone Work.-When cement mortar is used as a bedding, extreme care should be taken to select only such materials as will insure freedom from stain working out and disfiguring the face. Many so-called nonstaining cements are now on the market and are used for this purpose. The use of dirty sand may be as fully disastrous as a poor selection of cement and should be guarded against. Other protections against stain on the face are obtained through back painting with an asphaltum paint, or by plastering with a trowel coat of nonstaining cement mortar after the stone has been set and before backing up. Either or both of these methods is particularly essential if the backing is carried up in common cement mortar. Limestones are the easiest to stain, and when working with them, the most careful supervision should be accorded if good results are to be obtained.

57. Setting Stone Work.-The equipment for setting stone work varies with the type of building and the quantity of work involved. For rubble walls, either random or course, no particular equipment or plant will be required except for scaffolding to keep the mason abreast with his work, and stone barrows for delivering the stone within reach. An "A" frame for handling large sills or lintels may be useful. For course work where the size of the individua! pieces exceeds the capacity of the mason and his helper to handle individually, the “A” derrick with hand winch or drum is usually resorted to for all walls not exceeding three stories in height. When supplied with a good firm run plank, it is rapidly shifted from point to point and but two back guys are required, composed of one continuous piece of line running through three single sheave blocks, the two outer ones of which are attached to the head of the derrick, the center riding in the bight of the line, and will be attached to some convenient point at the foot of the derrick by means of a small watch tackle. The two outer ends of the line forming the guys are attached to suitable anchorage, a suitable sufficient distance back from the foot of the derrick to overcome any tendency to kick, and sufficient spread to avoid constant changing as the derrick is moved along the face of the work. By manipulating the watch tackle, one man at the foot of the derrick can control its action at all times.

58. Handling Stone.-Stones are picked up by the "Lewis" anchor or, where the "Lewis" holes would be objectionable such as in sills, by means of stone dogs and tongs. One mason and three riggers constitute the usual crew for such a derrick. Special dowel and anchor holes for inserting metal ties to bind in with the backing are generally cut in the field, and for this purpose one or more cutters will be required on a job of any size. They will also be required for fitting and back checking to overcome unusual conditions impossible to foresee at time of detailing. For high buildings, exceeding three stories, boom derricks are usually depended upon. On skeleton construction, the Chicago type of boom is used and a sufficient number installed to swing the entire frontage that is to be set. They should be hung as high up on the steel work as possible without getting in the way of the steel erectors, thus minimizing the number of jumps required to complete the entire front. To await the final completion of steel work and then set derricks on the roof, injects needless delay in the building's construction, and should not be considered. The power applied may be mechanical-supplied by steam or electric hoists or it may be manual, obtained through the aid of hand winches or windlasses set on the floor at the level of the derrick. For most work, the mechanical power is more desirable.

For wall bearing structures exceeding in height the range of the "A" type derrick, recourse is had to boom derricks set on platforms elevated by means of suitable towers. Such derricks will generally be set within the building lines and will be used in common by other trades whose work is dependent upon the progress of the walls.

On colonnades and other monumental fronts of sufficient length to warrant it, a device known as a "traveler" mounted on trucks and rails parallel to the building front, may be found useful. In effect, this device is an elevated, moving platform, self-sustained, on which is mounted one or two stiff-leg derricks with revolving booms. The dimensions on such a traveler are, of course, dependent on the range of work to be covered.

Inasmuch as the progress possible is directly proportionate to the number of setters employed, it has been found convenient on high buildings, where the element of time is a governing one, to dispense with the Chicago booms,

Sec. 5-59]

CONSTRUCTION METHODS

which do not operate advantageously on closer than 60-ft. centers, and substitute therefor the short "A" frame These used in conjunction with chain falls permit the use of a setter type, working from the inside and setting out.

on each and every pier, if necessary, and very rapid headway is thus accomplished. For this purpose the unset stones are hoisted to the various floor levels by large boom derricks, either as individual stones, if they are large, or in stone boats if they run to smaller sizes. They are then sorted on the floor and trucked or rolled out to the particular panels in which they are to be set, and there picked and dropped by the small "A" derricks to their final resting place.

59. Pointing Stone Work.-Stone work as a rule is not pointed as it is set. That operation is handled in conjunction with the cleaning down after the work has all been set out. Exterior hanging scaffolds are used, and starting at the top the work is thoroughly washed with clear water and stiff brushes. Although the use of washing powders is permissible, the practice of using acid, even in weak solutions, on any kind of stone, should be seriously condemned. All drippings, particularly on sills and projecting courses, should be cleaned off and all wooden wedges inserted by the setters should be removed. On limestones, a dry brushing with stiff wire brushes gives good results.

The pointing should only then be completed, using that type of joint selected, excessive care being exercised to see that the pointing mortar is shoved well back into the open joint to provide proper key.

60. General Precautions.-An observance of the following points will be found beneficial: All lug sills should be bedded on ends only, leaving full clearance through entire length between jamb lines. All metal anchors, other than those composed of brass or copper, should be thoroughly painted with some rust resisting preservative before inserting in the stone.

Overhanging courses should be provided with temporary support from below until sufficient weight of wall has been applied above to prevent tipping out.

All projecting courses and finished horizontal surfaces should be boxed and protected until danger from falling materials above has ceased.

Clean white sand only should be used in the mortar. Stone should not be laid in freezing or frosted weather. tions should be taken, otherwise spoiling of the face will result.

If the work must go ahead, then all known precau

Vertical joints in coping sills and projecting courses should be pointed full depth or grouted to give a complete seal against the weather.

When piling stone in the sorting yard, on the floor, or on the scaffolds, a firm, clean foundation should be provided and all setting identification marks exposed, so that the different pieces may be quickly recognized and obtainable without extra handling.

The endeavor should be made to have the work backed up as far as set out before leaving it for the night. On large panels built up from small pieces, best results Carving may be done either before or after setting. will be obtained by carving in place. There may also be considerable time saved by this latter method, thus compensating for the expense of scaffolds and protection to the carvers which otherwise would not be required at the building.

BRICK WORK

BY A. G. MOULTON

Bricks in one shape or another are common to nearly every type of building construction. They are used for structural as well as ornamental purposes. Used structurally as in bearing walls, it is seldom that the masonry will exceed 21 in. in thickness. From that down to 8 in. is the usual run of the work for the wall proper, with a 4 or 8-in. pilaster added to points where load is applied.

61. Location of Mortar Supply.—The mortar box, or mechanical mixer, as the case may be, should be set up so as to average the wheeling distance so far as possible to all points of the work proper. Its location also should be convenient for the delivery and storage of the dry ingredients and also close to the water supply.

Under ordinary conditions and where not over 12 masons are employed, hand-mixed mortar will be the most economical. Where from 12 to 20 masons are employed, either hand or machine mixed is equally good. For more than 20 masons, a machine mixer of the continuous type will give the best results.

The bond between the 62. Bonding Face to Backing.-For enclosing walls, the outer 4 in. may be carried up with a so-called face brick to obtain the desired architectural effect.

face and balance of the wall is accomplished in one of many ways and is generally a matter determined by the specifications.

63. Scaffolding. For stories of ordinary height, a horse scaffold, composed of the familiar 42-ft. mason horse and 5-plank deck, will be found the most convenient. Two sets high of this construction is the practical limit, however, except for short stretches. Hence, when walls exceeding 14 ft. between floor levels are encountered, it will be best to use the putlog scaffold composed of one line of upright supports at convenient centers (approximately, 7 ft.) set parallel and 6 ft. from the face of the work. Cross supports are attached thereto with inner ends bearing 4 in. on the wall and upon which the deck planking is laid. As this scaffold is dismantled, the putlog holes are filled up by the mason. This type of scaffold properly crossbraced will answer for almost any height of wall.

For face work, it is desirable to provide an outside scaffold if best results are to be insured, and particularly if a different kind of mortar is used on the face work from that used on the backing. All joints on face work should be struck, pointed, or raked out, according to the chosen design as the work proceeds and all backing should be topped out level with the face work, and the wall provided with temporary covering for weather protection before suspending for the day.

64. Swinging Scaffolds. For steel frame buildings, the patent swinging scaffold has become almost indispensable. Outriggers are projected along the face of the wall from the highest point available on the steel frame. These in turn support the scaffold machines, which are essentially small cast-iron drums actuated by trailing hand rope through the medium of worm gear and sheave. Wire cables attached to and suspended from the drums carry the scaffold proper. The cable capacity of the drums, usually 125 ft., determines the height the scaffold may be raised without resetting the outriggers and machines. The hand control ropes being of equal length to suspension cables, are always in reach of the scaffold men, who are constantly patrolling same and keeping it abreast of the walls and to the best advantage of the mason. Overhead protection, in the shape of light decking, should be provided on all such scaffolds whenever other trades are working at higher levels. The outer edge of the scaffold should be protected with a guard rail and light fence of poultry netting together with toc board.

On high buildings it has been found entirely practicable to keep the exterior walls within two stories of the finished floors at all times, providing all necessary materials have been properly scheduled for delivery as required.

If, due to unusual conditions, a delayed start is made necessary on the walls whereas the steel frame and arches have kept to normal progress, the gap thus produced can be closed by putting out a second scaffold at a higher level and working from both concurrently. To do this successfully, however, requires ample and well laid out hoisting facilities, so that no delay will ensue to the different sets of masons through waiting for materials.

65. Serving Materials to Masons.-The proper serving of materials to the mason while working from scaffolds is one of the most important factors to be watched. A scaffolding should be arranged so that the brick can be wheeled from the stock pile on the floor and by one transfer taken from the barrow and laid at the mason's feet. This arrangement, however, should not be at the expense of a heavy pull up a steep incline or runway. Under such conditions, two passes of the brick are to be preferred. Beyond this point, the brick hod must be depended upon. By keeping an even, constant flow of brick to the mason, not crowding up on him so as to restrict his foot space on the scaffold, and by keeping the tray always full of mortar, is the best way to insure satisfaction in the ranks and promote consistent output.

66. Material Elevators.-Brick, mortar, and other materials entering into the construction are elevated to the various working floors by means of platform hoists running up through temporary hatchways left in the floors, or in towers erected on the outer face of the work. Single platforms with capacity for two wheel barrows at a time are favored over the up-anddown type with one barrow to the load, because of the greater traveling speed obtainable. From 800 to 1000 ft. per minute is possible with the former type, and a greater margin of safety is provided for the operators. It is needless to say that riding on material hoists is an extremely dangerous practice and should not be permitted under any condition. For buildings over 12 stories high, it is customary to provide a temporary passenger elevator for the convenience of the workmen. This is generally erected in one of the permanent elevator shafts, using