discontinue the original permit. This causes old vaults to be carefully shored and incorporated within new vault framing when larger vaults are desired. Where this is the case the iron work of the old vault must be carefully inspected as to quality, strength and connections, considering in addition to the old load carried by the vault framing in place any extra load which may be thrown upon the old iron beams by means of connections of the new framing to the old beams in place.

7. Hoist Guides. Channel beams are often used in vault framing to keep in line the guides of the ash hoists or other sidewalk freight elevators. When I-beams are used around elevator shafts or around openings it is sometimes necessary to cut through one or both flanges of such beams to make room for the elevator guide rails. This arrangement will often weaken the sidewalk beam to an extent requiring reinforcement. The sidewalk beam may be reinforced by means of one or more plates well bolted to the top or sides of the beam. When the guide rail is heavy and bears at its lower end solidly like a strut, the beam may be reinforced by means of a knee angle placed under the beam and bolted to the guide rail.

CHAPTER XIV.

Erection and Inspection of Stairways

1. Inspection. Perhaps no part of a structure requires more attention from the part of the inspector or superintendent than the stairways. Any other part of the steel structure receives a large proportion of its final allowable load in the form of floor or wall dead loads, and the failure of such a beam will most likely be noticed long before it actually takes place, through the increased deflection or through cracks in the plastered ceiling below it. Furthermore such a failure may be of local importance, and the resulting damages might affect a small portion of a single floor.

On the other hand, consider what happens in the case of outside stairways. Their builder is paid after his work is completed and before these stairways have been made to carry practically any load except the dead load of the metalitself, which amounts usually to only one-tenth of the total load. In this way there is nothing to show by actual loading whether the stairway anchorage and connections could stand much more than the negligible weight of the iron itself. Furthermore, the effect of wind pressure will be a maximum when the stairs are fully loaded, and should the wind braces and other anchors fail to keep the stairs in position under these conditions, which may exist during a fire panic, the results would be nothing short of a calamity. For these reasons much attention must be paid to all details of the stairwork, and especially to the means used to secure such stairways to the main structure in such a manner as to exclude any remote possibility of a failure, when such stairs are fully loaded.

DEFINITIONS OF TERMS.

The various main parts of an iron stairway are as follows:

Stair Stringers. These are perhaps the most prominent part of the stairway. They are the inclined pieces or bars set edgewise as a support for the steps, and are generally made of a steel plate about eight to ten inches wide, set on edge, and reinforced along both edges by means of 14x14 inch angle irons. In a patented system the stair stringer and the reinforcing angle irons are replaced by a one-piece stringer, having the edges reinforced by buckling same in a rolling machine.

Stair stringers for exterior stairways should be not less than 4 inch in thickness. Stair stringers for interior stairways should be not less than 3/16 inch in thickness.

Bolted to the stringers are the Carriers, also called shelfangles. The carriers carry the steps of the stairway. Carriers are usually made of short angle irons bolted to the stair stringers with at least two bolts in each angle.

Steps usually consist of risers and treads. A Riser is an upright plate or board forming the vertical face of a step.

Treads are the horizontal boards or plates on which the feet tread.

The Rise of a stair is the vertical distance from the top of one step to the top of the next step. The total rise is the distance from one finished floor to the next finished floor.

The Run of a stair is the horizontal distance from the face of one riser to the face of the next riser. Treads are generally about 11⁄2 inches wider than the run, on account of the Nosing, or the overlaying projection of the tread beyond the face of the riser.

The Baluster is a fence-like arrangement supported by the stair stringers and preventing people from falling over the edges of the stairs. The baluster consists of a Hand Rail at its upper part, and of a number of Standards or filling-in bars, which run vertically between the stringer and the handrail every few inches apart. The standards may be either flat, round or square steel bars.

From distance to distance, and especially at turning points, heavy square or round Newel Posts are provided to reinforce the balusters.

Winders are steps wider near the outer edge and narrower near the centre of the stairway. They are essential elements in some systems of spiral stairways. Winders are not allowed in public stairways in office or loft buildings.

Exterior lines of stairways are sometimes continued to the roof of the building by means of usual stringers, steps and balconies. In other cases, a line of stairs may be brought up only to the top floor. Such stairways are sometimes continued to the roof by means of a vertical iron ladder fastened to the wall and curved over the parapet wall of the building. From the shape of their curved portions, such ladders are known as Goose-Neck Ladders. In place of iron steps these ladders are provided about every twelve inches in height with a round iron bar known as a Rung.

Interior lines of stairways are generaily continued to the roof by a stair of the same construction as the main body of

the stairway, and an enclosure provided with a full size door is usually provided at the upper end of the stairway. Such an enclosure is referred to as a Bulkhead.

Still in other cases the main stairway stops at the top floor, and the communication to the roof is made by means of a ladder running from any point on the top floor to a rectangular opening in the main roof. Such an opening is usually provided with a movable rain-cover and is known as a Scuttle.

The interior stairways have their stringers supported on the brick walls or connected to columns or to the steel floor beams of the main steel framing by means of round rods or Hangers.

Exterior stairways have their stringers supported on upright posts erected for the purpose. Such stringers are anchored to the main building by means of anchors bolted to floor beams or columns at the various floors. Balconies of exterior stairways are sometimes supported on Brackets. A bracket is shaped like a right-angled triangle, one short side of which is applied to the wall vertically and is securely anchored to the wall.

COMMON DEFECTS. Following are some of the common defects found in iron stairways. Some of these defects are found in both interior and exterior stairs, others in exterior stairs only.

1. Unpainted Iron. There is no reason why unpainted iron work should be erected. Certain parts, like those resting against walls, become inaccesible after erection. Furthermore, the material used in making the treads and risers for interior stairs is usually light steel plate, and this will often become seriously weakened by rust when exposed unpainted in the field. The inspector shall see that all iron work, including newel posts, treads and platforms shall be painted one coat of good paint before erection. Violations filed in such cases should not be recommended for dismissal until all holted connections have been loosened up and all stringers have been sufficiently displaced to allow of proper painting.

2. Incomplete Field Painting. Exterior stairways are often painted two coats after erection. In several instances it was found that where stringers rested alongside the face of a wall the painters made no effort to paint the surface of the stringer facing the wall. This, however, can be performed in most cases, especially when a row of windows happen te open along the stairway, or when the stringer is about four inches from the wall.

3.

Short Stringers. In good work a stringer resting on a brick wall will be provided with at least six inches of bearing. Four inches of bearing is common bad practice, and in some cases the stringers were made to rest on a lump of plaster.

All stringers having less than six inches bearing may be extended into the wall by bolting to the stringer a steel plate of the same depth as the stringer, and by using two or three one-half inch bolts in such connection. A 4x4 angle or a piece of a channel properly bolted may be used in place of the steel plate.

4. Cutting Stringers. It sometimes happens that a stringer is laid out wrong in the shop, and when erected it may project too far above the floor level or opposite a doorway. This projecting part is sometimes cut out, without reinforcing the remainder of the stringer. Although highly unsafe, such work is rather common.

5. Light Weight. Stringer plates, upright struts in exterior stairways, and very often treads, risers, platforms and newel posts are found to be light in weight. Stringers for exterior stairways are not allowed to be less than 4-inch in thickness; interior stair stringers must not be less than 3/16inch thick. This difference is due to the fact that the exterior stringers are more exposed to corrosion.

Width of Stairs. Exterior and interior stairways should be at least three feet four inches wide in clear. In some instances stairs three feet wide or less have been allowed, when such stairs are used for private purposes and are not the public stairways of the building.

7. Winders are allowed only in private stairways.

8. Head Room. A head room of about six feet in clear would be the minimum to be used in stairways or fire passages. On account of intricate arrangements in some buildings, the head room in fire passages on the first floor are sometimes found to be wanting in height and contrary to the approved plans.

9. Hangers. Interior stair stringers are often hung unto the main floor beams by means of flat or round steel hangers. Round bars three-quarter inches in diameter form excellent hangers. Such rods should be well bent at their upper end to catch the flange of the floor beam.

Some hangers may be bent cold or injured during bending or heating. For this reason the bent portion of each hanger should be carefully examined. Any flaw or serious check in the bend should be sufficient cause for rejection.