REPORT OF COMMITTEE ON BUILDING CONSTRUCTION
Ira H. Woolson, chairman; H. V. Thayer, secretary; W. F. Ballinger, Philip H. Bevier, D. K. Boyd, Wharton Clay, J. E. Curtis, J. E. Freeman, W. A. Hull, Richard L. Humphrey, John H. Kenney, Virgil G. Marani, R. P. Miller, Robert Palm, A. G. Patton, Chas. E. Paul, Walter Smedley, A. P. Stradling, R. E. Wilson. (This report has been submitted to ballot of the committee, which consists of nineteen members, of whom thirteen have voted affirmatively, one in favor of a portion and opposed to a portion, one negatively, and four have refrained from voting.)
Specifications for Construction of an Office Building—Grade E.
Definitions—An office building is one which is used for executive or clerical purposes, except for living rooms for the janitor, and is not used, above the grade floor, for the storage or exhibition of merchandise, nor in any part for manufacturing purposes.
A Grade E office building is one wherein the use, areas and exits fulfill the Grade A office building requirements, subject to certain restrictions in respect to height, and in which protected combustible materials are accepted as supporting members and certain modifications‘are accepted in the construction of floors and protected partitions.
Height—The height from grade to roof line shall not exceed 55 feet, nor more than four stories.
Area—The area within enclosure or fire walls shall not exceed the following:
Exits—W herever the word “exit” is used, it shall be one of the two following forms:
- Stair Exit: The direct connection of any floor area to an approved stairway built in conformity’ with the specifications hereafter detailed, either as (a), an enclosed interior stairway, or (b), a smokeproof tower.
- Horizontal Exit: The connection of any floor area through a fire exit partition, fire wall, or an open-air balcony or vestibule to another floor area in the same or an adjoining building having its own independent stair exits. Such other area shall be of sufficient size to contain temporarily the joint occupancy of the two areas thus joined.
In case of horizontal exits, each of the connected areas shall provide not less than three square feet of unobstructed floor space per person.
For the purpose of the requirements on exits, a floor area is any floor space enclosed on all sides by either the exterior walls, fire walls, or fire partitions.
Every story shall have at least two separate exits.
The occupants of every story above the first shall be provided with exits computed on the basis of at least 22 inches of width for every fourteen persons for stair exits, or 22 inches of width for every fifty persons for horizontal exits. At least one of the exits provided for every such floor area shall be a stair exit.
No width of exit stairway or passageway required by those rules shall be reduced at any subsequent point in the direction of exit travel. Exits shall be remote from each other, and no point of any floor area shall be more than 100 feet distant from an exit.
Assumptions—The allowable floor loads and wind stresses shall be such as to conform to the best engineering practice.
The allowable stresses, quality of all materials and workmanship shall conform to the best engineering practice.*
Working unit stresses for structural timbers used in dry locations shall be those given in the current specifications of the United States Forestry Service, and the net cross sections of timbers and not the nominal section shall be considered. In other cases where timber dimensions are mentioned, commercial or nominal sizes are referred to.
All girders or floor beams shall preferably be single stick timbers, but if double stick timbers are used, they shall be properly bolted together and contact faces shall be treated to prevent decay.
All work, whether construction or fireproofing, shall be installed under the supervision of a competent and reliable inspector.
All ceilings and all partitions (except intra-office partitions, for which there are no requirements) shall be constructed as hereinafter specified. There shall be no combustible lathing. Wood studs and joists shall not be over 16 inches C-C.
Highly silicious gravel as a coarse aggregate for reinforced concrete fireproofing shall not be used in portions of the building liable to be subjected to fire.
Wherever Fire Tests are referred to, they shall conform to the Standard Test Specification of National Fire Protection Association.
Foundation Walls—Foundation walls shall be built of hard burned clay brick or cement brick or stone, laid in cement mortar, or of concrete.
For one-story buildings, hollow building blocks of cement or clay may be used.
The construction of buried footings is not considered a part of these specifications.
Bearing Walls—All bearing walls shall be built of hard brick, meeting the requirements of the standard specifications for brick, properly laid and bonded, or of reinforced concrete or of other materials and construction meeting the two-hour fire test requirements.
Veneered walls shall not be permitted unless the veneering materials arc of equal fire resistance to the bearing wall and properly bonded, or tied thereto with non-corrodible metal wall ties.
* Note—For quality and kind of timber and durability, see the report on mill buildings. Sections 13-14. National Fire Protection Association (Proceedings 1917, page 419).
Exterior Walls—All exterior walls shall extend not less than three feet above the roof as a parapet, shall be the full minimum thickness and be properly coped, except that walls facing streets exceeding 40 feet in width may omit the parapet. In such case, provision shall be made to guard firemen from walking off the edge of the roof.
Non-Bearing Exterior Walls—Such walls carried on protected metal or reinforced concrete members may be of brick, stone, hollow tile or block. Veneering may be included in the required thickness of non-bearing walls, supported by such structural members.
Tarty and Fire Walls—All such walls shall be built of brick, meeting the requirements of the standard specifications for hard or medium brick of the A. S. T. M. properly laid or bonded, or of reinforced concrete or other materials and construction meeting the three-hour fire test.
All party and fire walls shall be continuous from the foundation to three feet above the roof, and shall be the full minimum thickness and shall be properly coped.
Where wooden beams enter walls on opposite sides, there shall be at least six inches of brickwork between the ends or sides of these beams, and in no case shall they enter the walls more than is required for sufficient support of the beams.
Thickness of Walls—All walls shall have a minimum thickness of 8 inches, if of reinforced concrete, 16 inches if of rubble stone, or 12 inches if of other material.
Bearing walls shall be increased in thickness in such proportion as may be required for greater bearing area or stability.
Ducts, chases or flues not exceeding one foot in width and not deeper than 25 per cent, of the minimum required thickness of a wall will be permitted, provided they are not nearer together than four feet, nor within four feet of any wall opening.
Allowable Openings in Walls—The maximum percentage of openings allowed in any exterior wall above the first story shall not exceed 40 per cent, of its superficial area per story.
There shall be not less than four feet of wall between openings in a vertical line.
Exterior window openings above the first story shall not exceed 50 square feet in area, and no single dimension shall exceed 10 feet.
No window opening shall be less than one foot from the ceiling surface, but the wall construction between the window opening and the ceiling may, if desired, be replaced by a fixed fire window.
Openings in fire walls shall not exceed 48 square feet in area, and the horizontal distance between adjacent openings shall be not less than nine feet.
Allowable Loads on Walls—The allowable load on walls shall not exceed the following in net tons per square foot:
Brickwork laid in lime mortar …………… 8 tons
Brickwork laid in cement lime mortar…….. 12 tons
Brickwork laid in Portland cement mortar … 15 tons
Rubble stonework laid in Portland cement mortar 10 tons
The permissible working stresses on hollow tile or concrete block when laid in Portland cement mortar, with cells either vertical or horizontal, shall not exceed one-tenth the average ultimate compressive strength of the tile or blocks based upon gross area, as shown by tests approved by the authorities having jurisdiction.
The unsupported height of a brick, hollow tile, or concrete block wall shall not exceed fifteen times the thickness unless adequately reinforced.
Walls Anchored—All walls shall be securely anchored or bonded at points where they meet.
Piers—Piers shall be built of hard burned clay brick or cement brick or stone laid in cement mortar, or of concrete.
If bonds are used in brick piers, they shall consist of perforated, rolled steel plates.
If cap-stones are used, they shall be protected against fire by four inches of fireproofing.
If a pier exceeds in height seven times its least dimension, it shall comply with the best practice in column designing.
Interior Columns—Interior columns shall be of such construction as will meet the requirements of the two-hour fire test. All column protection shall make close connection with the floors at top and bottom, and shall be so constructed as to leave no structural part of the column unprotected within the hollow space of the floor.
They shall be superimposed throughout all stories on approved column connection supports. Wood bolsters may be used to support roof girders only.
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No pipes, ducts or wires shall be placed within the area of the required fire protection of columns or beams.
Where columns are used in the first story to support exterior walls, metal ties shall be provided to prevent them from displacement if the floor is consumed.
Interior Partitions and Columns—All columns and bearing partitions shall be of such construction as will meet the requirements of the two-hour fire test.
The plaster at joining of partitions and ceiling shall, when required, be reinforced with metal lath four inches on each surface to avoid any tendency to open cracks if settlement occurs.
Bearing partitions and others extending into floors shall be fire-stopped by completely filling the hollow spaces between joists and between studs to a height of three inches above the floor level with loose incombustible material held in place by painted or galvanized sheet metal, metal lath or other material not easily disintegrated by water, so installed as to act as a ratproofing. If open mesh material is used, there shall be a thin layer of plaster to hold the loose material.
Non-bearing partitions shall not pierce the protective coating under ceiling joists unless fire-stopped within the floor in the above manner.
Floor and Roof Construction
The floor directly above the boiler room shall be built of incombustible material and of such construction as will meet the requirements of the two-hour fire test.
All other floors may be built of wood joists three inches thick, protected on the underside by incombustible lath and Portland cement plaster or such other protection as will render the floor system able to withstand the one-hour fire test. The joists shall be properly cut to allow release in case of fire, and well bridged at intervals of not over 5 feet; or floors may be of such other construction as will meet the one-hour fire test.
Pipe holes or other small openings through floors shall be surrounded by continuous metal sleeves properly flanged. Space between pipe and sleeve shall be so packed with incombustible material as to meet the requirements of the one-hour fire test.
Suspended or false ceilings under roofs shall be constructed to afford the same protection as that specified for wood floors.
Flat roofs shall be inclined sufficiently for proper drainage. Roofs may be constructed of similar materials to floors, but may be single thickness.
Roof Structures and Coverings—All structures above the roof shall meet the requirements of the one-hour fire test. Roof covering shall not be inferior to Class B roofing, as classified by the Underwriters’ Laboratories.
Stairway, Elevator and Other Shafts
Stairway, elevator and other shafts shall be enclosed as follows:
Walls of stair shafts shall be self-supporting and shall pass the requirements of the one and one-half hour fire test. Other shaft walls shall meet the one-hour test requirements.
Elevator doors shall be fire doors and be provided with approved safety devices so that door can be operated only when car is at landing, and car cannot move until door is closed. Stairway doors shall be self-closing.
The lobby leading to elevators and stairways shall be separated from other parts of building by a partition and fire doors, meeting the requirements of the one-hour fire test.
All shafts that extend into the upper story shall continue to a point three feet above the roof, and shall be of the same construction where they pass through the attic space. Should any shafts stop before they meet the top floor, they shall be covered with a horizontal structure equal in fire resistance to the floor construction.
Stairways—All exit stairs, landings and openings thereto shall have an unobstructed width throughout of at least 44 inches, except that hand rails may project not more than 3 1/2 inches into such width on each side.
There shall be not more than 12 feet vertically between landings.
All such stair landings shall be large enough to permit opening of the doors without interfering with traffic within the enclosure.
Suitable hand rails or banisters shall be provided on each side of each flight of stairs.
The treads and risers shall be uniform throughout and the treads constructed and maintained in a manner to prevent persons from slipping thereon.
All stairs and landings, if of wood, shall be protected on the under side by material giving one-hour protection.
No winders shall be allowed.
All stairways shall extend to the street level and open on the street, or to an unobstructed passageway affording safe egress to the street.
All exit stairs which extend to the top floor shall continue to the roof.
Stairways which may be used as a means of exit shall not extend continuously to floors helow the street level, unless partitioned off in such manner as will clearly indicate the street level, and unless the direction of egress to the street be plainly marked thereon.
Openings in stair, elevator and other shaft enclosures shall be protected by fire doors. The doors to stair shafts shall be selfclosing. Interior windows in stair or elevator shafts are prohibited.
All exit doors shall be self-closing and arranged to open in the direction of egress, and shall be equipped with approved hardware that can be operated in the direction of exit without the use of keys.
The doors of smoke-proof towers shall have a panel of wired glass not more than one-third the area of the doorway. All exits shall be properly and clearly marked.
Lighting—All stairway enclosures, smokeproof towers and exit passageways shall be lighted by either electricity or gas. If by electricity, the current shall be obtained either from a source outside the building or directly by independent circuit from the main switchboard. If by gas, the piping shall lead directly from the meter outlet to stairways without branches.
Vents, Skylights, Cornice and Gutters—These shall be constructed according to Recommendation of National Fire Protection Association, entitled, “Regulations Governing Roof Openings, Cornices and Gutters.”
Protection of Exterior Wall Openings
All exterior window openings exposed to buildings within 25 feet shall be protected by fire windows, or such other protection as may be approved for the purpose.
Where buildings or parts of the same building of different heights adjoin, all windows of the higher section above the roof of the lower section, as well as all windows within 10 feet of fire wall on each section, shall be protected in an approved manner.
Frames and sash of other windows may be of wood.
Exterior door openings exposed to buildings within 25 feet shall be protected by fire doors; other exterior doors may be of wood.
All windows on the story next above any mercantile occupancy shall be fire windows.
Protection of Interior Wall Openings
All openings in fire walls shall be protected with automatic ‘fire doors on each side of the wall.
If an opening in a fire wall is made to serve as an emergency exit, it shall not exceed 48 square feet in area and shall be not less than 44 inches wide and a self-closing fire door shall be substituted for one of the automatic fire doors.
Interior openings to ventilating shafts shall be protected by approved automatic trap doors or shutters.
All fire doors shall be mounted with approved hardware, and shall be securely attached to the wall or partition or to approved frames anchored thereto.
The room or rooms in which boilers and all power and operating machinery are located shall be separated from other portions of the building by a 12-inch brick or 8-inch reinforced concrete wall, having an automatic fire door at each opening, and such rooms shall not have direct communication with the floor above. The floor over such rooms shall be of incombustible material and meet the requirements of the two-hour fire test.
A standpipe shall be installed at each stair enclosure. The installation of standpipe and hose shall conform to the requirements of the standards established by the National Fire Protection Association.
Where any portion of the building on the grade floor, or any floor below the grade is used for the storage or exhibition for sale of merchandise, an approved automatic sprinkler equipment shall be provided in such portion.
All electrical equipment shall be installed in accordance with the requirements of the National Electrical Code.
All heating, ventilating and other service equipment shall be separated from other portions of the building by enclosing walls meeting the requirements of the three-hour fire test, and all openings in same shall be provided with approved fire doors.
Where the heating is by blower or indirect systems, the ducts shall be substantially constructed and supported, and shall be insulated with satisfactory incombustible covering not less than 1/2 inch thick. The ducts shall be provided with approved automatic cut-off devices, and in other respects shall comply with the “Regulations for Blower Systems,” recommended by the National Fire Protection Association.
Where gas is supplied for heating or lighting purposes, metal pipes shall be used throughout with properly located valves. Any material of an inflammable nature shall be protected from the flame or heat of the gas lighting, heating or ventilating apparatus by metal and asbestos or other fireresistive, non-conducting material. Where gas is supplied, approved outside cut-off devices shall be provided. No swinging gas fixtures shall be used.
Chimneys and Flues
All chimneys and flues shall be constructed in accordance with the requirements of the Chimney Ordinance of the National Board of Fire Underwriters.
Roof tanks may be supported on wood or unprotected steel supports.
Appendix to Grade “E”
Materials and construction called for in these specifications shall meet the standards approved by the American Engineering Standards Committee or of the American Society for Testing Materials; U. S. Bureau of Standards; National Fire Protection Association, or the National Board of Fire Underwriters.
Where none of these organizations has established standards, the specifications of the Associations of the various industries shall be considered as recommended practice when approved by the Committee.
Pending the adoption of standards by one of the above mentioned organizations, the specifications of the Hollow Building Tile Association shall govern the use of that material, and those of the American Concrete Institute the use of reinforced concrete, concrete block and concrete brick, where and as the iise of these materials is allowable within these specifications.