FLORIDA BUILDING CODE BCT 1760

Transcription

1 FLORIDA BUILDING CODE BCT 1760 CHAPTER 5 FIRE-RESISTANT-RATED CONSTRUCTION MICHAEL KNOTEK 68

2 FIRE-RESISTANT-RATED CONSTRUCTION FIRE WALLS Each portion of a building separated by one or more fire walls shall be considered a separate building. Fire walls dividing buildings into separate buildings shall provide a 4-hour fire resistance rating Fire walls shall have sufficient structural stability under fire conditions to allow collapse of construction on either side without collapse of the wall for the duration of time indicated by the fire resistance rating. TOWNHOUSE FIRE SEPARATION Each townhouse shall be considered a separate building and shall be separated from adjoining townhouses by a party wall of 4-hour rating or by the use of separate exterior walls meeting the requirements of Table 601 and 602 for zero clearance from property lines as required for the type of construction Separate exterior walls fire separation shall include one of the following: A parapet not less than 18 above the roof line Roof sheathing of noncombustible materials or fire retardant treated wood, for not less than 4- foot width on each side of the exterior dividing wall One layer of 5/8 inch Type X gypsum board attached to the underside of roof decking, for not less than a 4 foot width on each side of the exterior dividing wall EXTERIOR WALLS Exterior walls shall be fire-resistance rated accordance with Table 601 and 602 The fire resistance rating of exterior walls with a fire separation distance of greater than 5 shall be rated for exposure to fire from the inside The fire resistance rating of exterior walls with a fire separation distance of 5 or less shall be rated for exposure to fire from both sides ROOF OVERHANGS, CORNICES, ETC. Roof overhangs, cornices, etc., shall be of noncombustible construction for buildings of Type I and II construction. For Types III, IV, and V construction, the projections may be combustible or noncombustible construction. 69

3 PROTECTION OF OPENINGS Wall openings require protection to restrict the spread of smoke and fire within buildings, whether from internal or external fire exposure Except in Group R3 occupancies, such as one and two family dwellings, openings in exterior walls have to be protected. Exceptions: PARAPETS Every exterior wall within 15 ft. of a property line shall be equipped with approved opening protectives. Exterior walls not required by Table 601 to have a fire resistance rating. Show windows fronting on a street or public space Opening parking structures Parapets shall be provided on exterior walls of buildings Exceptions: A parapet need not be provided on an exterior wall where any of the following conditions exist: The wall is not required to be fire-resistance rated in accordance with Table 602 because of fire separation distance The building has an area of not more than 1,000 square feet on any floor Walls that terminate at roofs of not less than 2-hour fire-resistance-rated construction or where the roof, including the deck and supporting construction, is constructed entirely of noncombustible materials VERTICAL SEPARATION OF OPENINGS Flame barriers are required to obstruct the passage of flames from floor to floor where openings are within 5 of each other horizontally and the openings in the lower story are not protected openings. The flame barrier may be either a 30 noncombustible horizontal projection beyond the exterior wall in the plan of the floor, or a vertical flame barrier of 3 ft. measured vertically above the top of the lower opening. Even though the horizontal projection must be noncombustible, regardless of the type of construction, the vertical flame barrier need only be a material consistent with the type of construction of the building. Flame barriers are not required when the building is equipped with an approved automatic sprinkler system. 70

4 FLAME BARRIERS APPROVED TYPES OF FIRE WINDOWS, DOORS AND SHUTTERS Wall openings required to be protected shall be protected by approved listed and labeled fire doors, windows, and shutters and their accompanying hardware, including all frames, closing devices, anchorage and sills, in accordance with the requirements of NFPA 80 Opening protective s is classified base on the fire conditions to which they are expected to be exposed. Fire doors are classified as 3 hour, 1 ½ hour, 1 hour, ¾ hour or 20 minute Automatic or self-closing devices are required for fire rated doors. Doors which connect adjoining guest rooms in hotels or motels are not required to have any closing devices, since the door will be closed when rooms are occupied by separate tenants. FIRE SHUTTERS A shutter is a labeled door assembly that is used for the protection of a window opening in an exterior wall. They are fire doors without glass lights They may be swinging doors, horizontally or vertically sliding doors, or rolling steel doors. Each must be equipped to automatically close At least one-third of the swinging type shutters used on each story facing the street must be distinguishable and readily openable from the outside for ready access by fire fighters. 71

5 VIEW PANELS Table gives, general, non-tested, non-labeled area and dimension limitations for wired glass used in fire rated doors. The glass must be fully embedded in putty, and the joints must be struck and pointed in order to allow expansion and prevent migration of smoke and hot gases through the joint. VIEW PANELS View panels are allowed in walls with a required fire resistance of 1-hour maximum and shall consist of one of the following: ¼ thick labeled wire glass assemblies installed in steel frames. The wired glass shall be limited to 1,296 sq.in. with no dimension greater than 54 Labeled glass block panels installed in steel channels. The glass block shall be limited to 120 sq.ft. with no dimension greater than 12 Other glazing materials which have been tested and labeled to indicate the type of opening to be protected for fire protection purposes In walls separating corridor from tenant spaces, the viewing panels cannot exceed 25% of the wall area. PROTECTION OF PENETRATIONS INTERIOR WALLS Protection of penetrations through fire rated and non fire rated assemblies is required Where sleeves are used, the sleeves shall be securely fastened to the assembly penetrated. All space between the item contained in the sleeve and the sleeve itself and any other space between the sleeve and the assembly penetrated shall be protected. 72

6 PENETRATIONS OF FIRE RATED WALLS Annular space is that space between a penetrating item and the rated assembly The annular space must be filled with an approved material that prevents the passage of flames and hot gases sufficient to ignite cotton waste MEMBRANE PENETRATIONS The separation requirement for electrical boxes on opposite sides of a wall is intended to prevent aligned penetrations on both sides of the wall. The 24 horizontal separation effectively places the boxes in separate wall cavities for wood and steel stud walls. The metal outlet or switch boxes should be securely fastened to the studs, and the opening in the wallboard facing should be cut so that the clearance between the box and the wallboard does not exceed 1/8 73

7 FIRE DAMPERS To maintain the fire resistance of a wall, partition, or shaft, ducts that penetrate such fire rated assemblies must also be effective in resisting the spread of smoke and fire. The damper may be omitted if the duct system is for the exhaust of air to the outside and serves only one floor. However, if the duct penetrates a wall or partition with a fire resistant rating of two hours or more or passes through a shaft enclosure, the damper would be required. SMOKE BARRIERS An approved damper designed to resist the passage of smoke shall be installed at each air transfer opening or duct penetration of a required smoke barrier. Smoke dampers located in ducts that penetrate smoke barriers shall close upon detection of smoke by smoke detectors Required smoke dampers in air transfer openings shall close upon detection of smoke by smoke detectors that are installed in accordance with NFPA 72. FIREBLOCKING The danger of fire spread through continuous vertical and horizontal concealed spaces has been substantiated numerous times. Uncontained by fire blocking and draft stopping, a fire can rapidly spread throughout the concealed spaces within the components of a building, encompassing the entire building in a short time In all construction, whether combustible or noncombustible, fire blocking ids required to separate the vertical from the horizontal concealed spaces. The intersection of such spaces typically occurs at the intersection of walls with floor/ceiling assemblies. COMBUSTIBLES IN CONCEALED SPACES Structural members of Types I, II, and IV construction are required to be noncombustible. The use of combustibles in non-structural applications is limited to prevent fire spread within building elements. The severity of a potential problem increases when combustibles are located within concealed spaces and are inaccessible to manual firefighting. The code regulates the use of combustibles within concealed spaces of noncombustible buildings. 74

8 DRAFTSTOPPING Draft stopping is another measure taken in combustible construction to contain flame spread through horizontal concealed spaces. The materials and their proper installation should prevent the movement of hot air, gases, and flame across the barrier Draft stopping is not required in noncombustible construction, such as open web steel joist construction. Care must be taken during the life of the building to maintain the integrity of draft stopping from penetrations during the installation of cable and other utility systems SHAFT ENCLOSURES SHAFT ENCLOSURES It is important to recognize the terminology for shafts and enclosures Shafts are the floor openings, and Enclosures are the walls that surround such openings. Enclosures are used to protect shafts in multistory buildings so that smoke and hot gases, and eventually the fire, do not enter the shaft and travel from floor to floor. For those shafts housing items that may cause a fire, such as electrical cables and kitchen exhaust ducts, the enclosure acts to contain the fire. SHAFT ENCLOSURE CONSTRUCTION The fire resistance rating of the shaft enclosure walls must be as required by Section or equivalent to the rating of the floor assembly penetrated, whichever is the greatest, but the rating need not exceed 2 hours. EXAMPLE Consider a Group B unsprinklered building of Type I construction with a shaft that penetrates two floors. Section requires a 1-hour shaft enclosure Table 601 requires the floor/ceiling construction to be 3-hour rated Solution: Therefore, a 2-hour shaft enclosure and 1 1/2 hour opening protectives are required. 75

9 ENCLOSURE AT TOP Where shafts terminates below the roof, an enclosure at the top is required to insure protection against the fire spreading to the stories above Where termination is trough a combustible roof, the shaft enclosure wall is extended at least 36 inches above the highest part of the roof to form a parapet to protect the roof from a fire within the shaft ENCLOSURE AT BOTTOM Shafts which do not extend to the bottom of the building or structure shall be enclosed at the lowest level with construction of the same fire resistance as the lowest floor through which the shaft passes, but not less than the rating required for the shaft enclosure, or shall terminate in a room having a use related to the purpose of the shaft. CALCULATED FIRE RESISTANCE This portion of the code contain procedures by which the fire resistance of specific materials or combinations of materials can be established by calculations EXAMPLE GIVEN: The exterior wall assembly in the figure below has a layer of 15/32 wood structural panel bonded with exterior glue covered with a layer of 5/8 gypsum wallboard and attached to studs spaced at 16 o.c. FIND: Does the wall assembly qualify as a 1-hour resistant wall assembly? 76

10 SOLUTION from Tables: 15/32 in wood structural panel bonded with exterior glue - 10 min. 5/8 gypsum board - 30 min. Wood studs 16 o.c min. 60 min. Therefore, the wall does qualify as a 1-hour wall SOLUTION It should be noted that if the wall cavities between the studs had been filled with mineral fiber batts, the 15/32 plywood membrane layer could be eliminated because the insulation will add 15minute of fire resistance. Thus, adding the contribution times for the 5/8 gypsum board, the wood framing, and the insulation (30 minutes + 20 minutes + 15 minutes), the resultant rating for the wall would be 65 minutes and meet a 1-hour fire resistant rating 77