System Design Considerations - USG

1 29310 System Design ConsiderationsSystem Technical DataCGC leads the industry in developing high-performance systems tomeet specialized requirements for modern building Design and in doc-umenting their performance at recognized testing laboratories. Thesesystems provide fire resistance , sound control, structural capacity andesthetics for improved function and utility while reducing constructiontime and cost. All are constructed of quality products and released onlyafter thorough testing and field most instances, fire resistance and often sound-attenuation perfor-mance applies equally to systems constructed with gypsum panels andgypsum bases. Gypsum base with veneer plaster finish provides anacceptable alternative to gypsum panels. Therefore, the term gypsumboard is used throughout this chapter to refer to both types of where performance differs greatly are the products treated CriteriaDesign of any structure must take into account the kinds of conditionsthat will exist and the resulting stresses and movements.

2 Load-bearingwalls include the exterior walls of a building and some interior walls,too. These structures must be designed to carry the weight of thestructure, its components and other loads that occur once the buildingis amount of axial load that structural members can bear will varywith the amount of lateral load (pressure from wind or other horizontalstresses) that the final assembly may of structural components, particularly steel framing (studs,runners, joists) provide tables that identify the maximum allowable loads forvarious components under specific conditions. These tables typically startat 240 Pa (5 psf) lateral loads and increase in 240 or 480 Pa (5 or 10 psf)increments to about 1920 Pa (40 psf). Interior partitions are typicallydesigned for 240 Pa (5 psf) lateral non-bearing partitions are not designed to carry axial heights are based on stress or deflection limits for given lat-eral loads.

3 Height limitations depend on the gauge of the steel used,dimensions of the stud, stud spacing and the allowable deflection walls are not regarded as load-bearing walls and are notdesigned to carry axial loads. However, finished curtain wall assembliesdo need to withstand wind loads within certain stress or deflection lim-its. Limiting height tables from the framing manufacturer should capacity of steel studs are based on the following factorsas applicable:1. AISI Specifications for the Design of Cold-Formed Steel Yield strength of the Structural and physical properties of Bending stress of the steel Axial load on the Shear stress of the Allowable deflection of the Web crippling of stud at Lateral SelectionSelection of a stud gauge and size must take into account a number offactors. The key consideration is whether the assembly is for a load-bearing, nonload-bearing or curtain wall application.

4 Other variablesinclude anticipated wall height, weight and dimensions of mounted fix-tures, fire rating desired, sound attenuation needed, anticipated windloads, insulation requirements, deflection allowance and desiredimpact general, stronger or heavier studs are needed to accommodate tallerwalls. Stronger studs also reduce deflection and vibration from impactssuch as slamming doors. Wider studs may be required to handle insu-lation requirements. fire -rated systems are usually designed, testedand classified based on using the lightest gauge, shallowest stud depthand maximum stud spacing as indicated in the assembly gauge and depth may be increased without affecting the fire - resistance rating of the and performance characteristics can be achieved in a varietyof ways. Wall strength can be increased by using heavier gauge mate-rial, stronger stud designs, narrower stud spacing or larger web dimen-sions.

5 Studs typically are selected to maintain cost control and designintegrity. Increased strength requirements generally are met by firstincreasing steel gauge or stud style before increasing stud studs are typically manufactured in two different styles: Studs designed for nonload-bearing interior drywall partition applica-tions have a minimum 32 mm (1-1/4 ) flange width on both sides. Theweb Design incorporates a cutout for bracing and for electrical,communication and plumbing lines. Studs designed for load-bearing drywall partition applications have aflange width of 41 mm (1-5/8 ). Cutouts in the web accommodatebracing, utility service and mechanical specific stud Design and assembly information, consult CGCT echnical Folder SA923,Drywall/Steel Framed and Sound TestsFire and sound test data aid in comparing and selecting materials andconstructions.

6 In addition, these data frequently are essential for secur-ing acceptance by the building code or agency having jurisdiction. TheCGC Construction SelectorSA100 provides tested fire resistance andacoustical performance for various Design Considerations10 fire resistance refers to the ability of an assembly to serve as a barrier tofire and to confine its spread to the area of origin. Spread of fire from onearea to another occurs because (a) the barrier collapses, (b) openings inthe barrier allow passage of flame or hot gases or (c) sufficient heat is con-ducted through an assembly to exceed specified temperature characteristics form the basis for judging when an assembly nolonger serves as a barrier in a fire - resistance ratingdenotes the length of time a given assembly canwithstand fire and give protection from it under precisely controlled labo-ratory conditions. All tests are conducted in accordance with the StandardMethod of fire Endurance Tests of Building Construction and Materials,CAN/ULC S101 and Standard, fire Tests of Building Construction andMaterials, ASTM E119.

7 The ratings are expressed in hours and apply towalls, floor- and roof-ceiling assemblies, beams and assemblies tested at Underwriters Laboratories Canada Inc. (ULC) orUnderwriters Laboratories Inc. (UL), ratings are specific to the designs test-ed. Unless described in the Design , insulation may not be added to floor-or roof-ceiling assemblies under the assumption that the rating either willremain the same or improve. Addition of insulation in the concealed spacebetween the ceiling membrane and the floor or roof structure may reducethe hourly rating of an assembly by causing premature disruption of theceiling membrane and/or higher temperatures on structural componentsunder fire exposure offers both ULC and UL fire resistance rated assemblies. All ULdesigns referenced are listed in UL s Directory Products Certified forCanada. The Standards Council of Canada recognizes UL as an organiza-tion certified to investigate products and systems to Canadian standardssuch as CAN/ULC S101.

8 All CGC panel and grid products carry both theULC and cUL labels. CGC ceiling tiles and panels carry the cUL label. Thisverifies that these UL assemblies fully comply with national, provincial andterritorial building Sound Transmission Class (STC)is a widely used rating of soundattenuation performance for transmission through an assembly accurate for speech sounds but not for music, mechanical equipmentnoise or any sound with substantial low-frequency energy. It is testedper ASTM E90 and rated per ASTM Impact Insulation Class (IIC)is a numerical evaluation of a floor-ceilingassembly s effectiveness in retarding the transmission of impact sound,also determined from laboratory testing. IIC is tested per ASTM E492 andrated per ASTM Noise Reduction Coefficient (NRC)is a measure of sound absorption. Thisis an important consideration for controlling acoustics within a confined Ceiling Attenuation Class (CAC)applies to acoustical ceilings andis tested per ASTM E1414 for horizontally adjacent and sound tests are conducted on CGC products assembled in a specif-ic manner to meet requirements of established test procedures.

9 Substitutionof materials other than those tested or deviation from the specified construc-tion may adversely affect performance and result in failure. For completeinformation on test components and construction, see the test information about fire and sound testing can be found in fire A large number of systems have been designed and tested for fireSystems resistance . The systems vary greatly in both Design and , certain basic System designs are commonly used. As aframe of reference, several typical designs and their accompanying fireratings are shown below for wood-frame and steel-frame , in most tests, there are options that make them more , there are certain limitations that should be considered. Below area series of notes that apply to many of the fire tests:1. Two recent tests permit SHEETROCKB rand Gypsum Panel products andGRANDPRIXB rand Plaster Base products to be applied horizontally orvertically in partitions without compromising the fire rating.

10 These testsare UL Design U419 for non-load-bearing partitions and UL DesignU423 for load-bearing partitions. When either of these tests are listedwith a CGC System , it means that the System can now be built with thepanels oriented in either The two fire tests indicated above also demonstrated that whenFIRECODEor FIRECODEC Core products are used, the horizontal joints onopposite side of the studs need not be staggered (as was previouslyrequired).3. In partitions indicating the use of mm (1/2 ) DUROCKB rand CementBoard it is permissible to substitute mm (5/8 ) DUROCKB randCement Board without compromising the fire In partition and ceiling systems indicating the use of mm (5/8 )SHEETROCKB rand Gypsum Panels, FIRECODECore, or mm (1/2 )SHEETROCKB rand Gypsum Panels, FIRECODEC Core, it is permissible tosubstitute mm (5/8 ) FIBEROCKB rand Abuse-Resistant Panelswithout compromising the fire Where thermal insulation is shown in assembly drawings, the specificproduct is required to achieve the stated fire rating.