Fire Resistance Bulletin 2 - MBMA

1 Fire ResistanceBulletinMetal Building Manufacturers Resistance Ratings for Exterior Walls U. L. Tested and Classified For 1 and 2 HoursInsurance Bulletin No. 5 explains how insurancerates for metal buildings are affected by exteriorwall construction. Fire Resistive Bulletin #1 (for-merly listed as Insurance Bulletin #6) explainshow insurance rates can be improved by using and classified 1, 1 and 2-hour fire protect-ed meetings and discussions with InsuranceServices Office headquarters and through fieldexperience it was determined that although the pro-tected columns were providing an improved insur-ance rate, they were still not producing rates thatwould be directly competitive with buildings withconcrete block exterior walls.

2 Therefore, theMBMA Committee on Fire Protection and RelatedInsurance Matters undertook an engineering analy-sis and testing program to establish fire resistantrated exterior walls are listed by UnderwritersLaboratories, Inc. in the 1996 Fire ResistanceDirectory as Design No. addition to improving fire insurance rates, fireresistant exterior rated walls are helpful in meetingbuilding code requirements, including lot line sep-aration and set-back requirements. The BOCAN ational Building Code published by the BuildingOfficials and Code Administrators International,Inc.

3 Require that exterior walls having a 5 foot orless fire separation to the closest interior lot line, tothe centerline of a street or public way or to animaginary line between two buildings on the sameproperty, be rated for exposure to fire from bothsides. Where the fire separation distance is greaterthan 5 feet, the exterior wall needs only be ratedfrom the inside (Section ). The same requirement is in the Standard BuildingCode published by the Southern Building CodeCongress International, Inc. (Table 600, note i).

4 Design No. U425 details the wall constructionand gypsum wallboard protection. DesignU425 is also included in this with the fire rated columns, MBMA considersthis a breakthrough in fire protection research ofgreat importance to the designers and users of eco-nomical light steel frame No. U489 Bearing Wall Rating - 1, 1 and 2 on next pageNote: This Bulletin was previously released as Insurance Bulletin #16 Metal Building Manufacturers No. U425(For Exterior Walls, Ratings Applicable ForExposure To Fire On Interior Face Only)(See Items 4 and 5)Bearing Wall Rating - 45 Min.

5 , 1, 1 or 2 Protection - See Design Nos. X524and X530 for column -"Z" or "C" shape girts fabricated to in. thick steel. Girts shall be 6 to10 in. deep with 2 to 3 in. Clips -Fabricated from min. steel, angles may be bolted to columnswith by 1 in. bolts and nuts or may beplates shop-welded to Wall Panels -No. 26 MSG min. Construction -See Design No. U425 Top of the wall shall be against the undersideof roof All openings between top of wall and roofdeck are to be filled with UL Classified miner-al wool or glass fiber Steel studs in accordance with the specifica-tions in Design No.

6 - Min. in. (25 gauge) thick gal-vanized steel, 1 5/16 in. wide on top and2 in. wide at bottom by 7/8 in. deep (hat sec-tion), spaced 48 in. max. *Bearing the UL Classification MarkingSteel Floor and Ceiling Tracks(Not Shown)- Top and bottom tracks of wall assembliesshall consist of steel members, min. No. 20 GSG ( in. thick) galvanized steel or MSG ( in. thick) primed steel, thatprovide a sound structural connection betweensteel studs, and to adjacent assemblies such asa floor, ceiling, and/or other walls. Attached tofloor and ceiling assemblies with steel fasten-ers spaced not greater than 24 in.

7 On next pageMetal Building Manufacturers Studs -Corrosion-protected steel studs,min. 3 in. wide, min. No. 20 GSG ( ) galvanized steel or No. 20 MSG ( thick) primed steel, cold-formed, shall bedesigned in accordance with the current editionof the Specification for the Design of Cold-Formed Steel Structural Members by theAmerican Iron and Steel Institute. All designdetails enhancing the structural integrity of thewall assembly, including the axial design loadof the studs, shall be as specified by the steelstud designer and/or producer, and shall meetthe requirements of all applicable local codeagencies.

8 The max. stud spacing of wall assem-blies shall not exceed 24 in. (or 16 - See Item 5c). Studs attached to floor andceiling tracks with in. long Type S-12 panhead, self-drilling, self-tapping steel screws on both sides of studs or by welded or bolted con-nections designed in accordance with the Support Members (Not shown) -Where required for lateral support of studs,support may be provided by means of steelstraps, channels or other similar means as spec-ified in the design of a particular steel stud , Gypsum* - Gypsum wallboardbearing the UL Classification Marking as toFire Resistance .

9 Applied vertically with jointsbetween layers staggered. Outer layer of 3layer construction may be applied thickness and number of layers and per-cent of design load for the 45 min., 1 hr., 1 hr and 2 hr ratings are as follows:Interior Walls (Wallboard Protection Both Sides of Wall)RatingNumber of Layers andThickness of Boards in Each LayerPercent of Design Load45 min.* 1 layer, in. thick1001 hour* 1 layer, 5/8 in. thick1001 hr.* 2 layers, in. thick1002 hours* 2 layers, 5/8 in. thick80* 3 layers, in. thick or 100* 2 layers, in.

10 Thick100 RatingNumber of Layers andThickness of Boards in Each LayerPercent of Design Load45 min.* 1 layer, 5/8 in. thick1001 hour* 2 layers, 1/2 in. thick1001 hr.* 2 layers, 5/8 in. thick1002 hours* 3 layers, 1/2 in. thick or100* 2 layers, 3/4 in. thick100*Ratings applicable to assemblies serving as exterior walls where Classified fire resistive gypsum sheathing type wallboard is substituted on the exterior Walls (Wallboard Protection On Interior Side of Wall) *Bearing the UL Classification MarkingContinued on next pageMetal Building Manufacturers ResistanceBulletinSee Wallboard Gypsum (CKNX)Category fornames of Classified Companies of in.