Some basic rules <strong>of</strong> prescriptive bracing in SeismicDesign Category D 2 are shown below. Many <strong>of</strong> the basicrules do, however, have exceptions that allow limitedmodification <strong>of</strong> the requirements. A double asterisk**below, signifies that exceptions exist, that will bediscussed in more detail later in this document.Braced Wall Lineso Every ro<strong>of</strong> and floor must be supported on allsides by braced wall lines.**o Braced wall lines must be placed across thebuilding at least every 25 feet.**o Braced wall lines may have <strong>of</strong>fsets <strong>of</strong> up to 4 feet(in each direction) along the length <strong>of</strong> the bracedwall line.o Braced wall lines must be perpendicular to eachother.o Buildings longer than 50 feet must havecontinuous footings and foundations under theinterior braced wall lines.**o If cripple walls are used (wood walls between thefoundation and the first floor framing) they mustbe constructed as braced wall lines andconsidered as an additional story if over 4 feettall.o Braced wall lines must have at least 25% <strong>of</strong> thewall area constructed as braced wall panels forsingle story buildings, or the top floor walls <strong>of</strong> atwo-story; and 55% <strong>of</strong> the wall area constructedas bracing on the first story walls <strong>of</strong> a two storybuilding.**Braced Wall Panelso Braced Wall panels must be at least 48 incheslong (plywood or OSB).**o Braced wall panels must be located at the ends <strong>of</strong>every braced wall line.**o Braced wall panels must be located at least every25 feet on center along every braced wall line.**o Braced wall panels may be constructed by anyone <strong>of</strong> seven allowable methods found in IRCSection R602.10.3, though the most commonmethods <strong>of</strong> braced wall panel construction aremethod #3, wood structural panel sheathing,(plywood or OSB) and method #5 for interiorwalls using gypsum wall board.o Required braced wall panels may be replaced by“Alternate Braced Wall Panels” that can be assmall as 2 feet 8 inches long.Braced Wall Panel LocationsBraced wall lines shall consist <strong>of</strong>braced wall panels that meet therequirements for location, type, andamount <strong>of</strong> bracing specified in the table below, and arein line or <strong>of</strong>fset from each other by not more than 4'.Braced wall panels shall be located at the end <strong>of</strong> eachbraced wall line, or may start up to 8 feet from the endprovided certain conditions are satisfied. All bracedwall panels shall be clearly indicated on the plans.Braced WallPanel LocationOne Story,or top story <strong>of</strong> atwo storyFirst Story <strong>of</strong> atwo storyCripple Wallsless than 48” tallIRC R602.10.3ConstructionMethod(s)2,3,4,5,6,7 or 82,3,4,5,6,7 or 8Method 3Bracing RequirementsLocated at each end and atleast every 25 feet on centerbut not less than 25% <strong>of</strong>braced wall line for Method 3and 40% <strong>of</strong> braced wall line forMethods 2,4,5,6,7 or 8.Located at each end and atleast every 25 feet on centerbut not less than 55% <strong>of</strong>braced wall line for Method 3and 75% <strong>of</strong> braced wall line forMethods 2,4,5,6,7 or 8Located at each end and atleast every 25 feet on centerbut not less than 75% <strong>of</strong>braced wall line.Braced Wall Panel ConstructionIRC Section R602.10.3 specifies 8 different methods toconstruct braced wall panels, however, in Seismic DesignCategory D 2 area, only Methods 2 through 8 areallowable. Method 3 is by far the most common method,and Method 5 is frequently used for interior braced wallpanels; they are described below. The other methods arenot described in this handout, however could be used.For the other methods, please see IRC Section R602.10.3.• Method 3: Wood structural panel sheathing witha thickness not less than 5/16" for 16" studspacing and not less than 3/8" for 24" studspacing. Wood structural panels shall be installedin accordance with IRC Table R602.3(3). SeeFigure 4)• Method 5: Gypsum sheathing, minimum ½ inchthickness, placed on studs spaced a maximum <strong>of</strong>24 inches on center and fastened with 1 ½ inchgalvanized ro<strong>of</strong>ing nails or 6d common nails at 7inches on center throughout; Or, gypsumwallboard (interior) fastened with 5d cooler nailsspaced 7” on center throughout.(See Figure 5)All vertical joints in braced wall panels shall occur overthe studs; all horizontal panel joints shall occur overblocking at least 1½ inches thick.#62—<strong>BRACED</strong> <strong>WALL</strong> <strong>PANELS</strong>Page 2
FIGURE 4:TYPICAL PRESCRIPTIVE <strong>BRACED</strong> <strong>WALL</strong> PANEL(per IRC Section R602.10.3, Method #3)4'-0" min.2 - 2x Top plates.Stagger joints 4'-0" min.Nail 16d at 16" oc.2x studs spaced 24" o.c. max. End nail studto top plate with 2-16d nails. Nail stud to sillplate with 4-8d toenails or 2-16d end nail.Wood structural panel sheathingminimum 5/16" thick for studs 16" oc.and minimum 3/8" thick for studs 24" oc.10'-0"Max.2x Blocking installed against sheathing andnailed to studs with 16d nails. Nail sheathingat 6 inches on center at panel edges and12 inches on center in the panel field.2x sill plate nailed to joist or blockingwith 3-16d nails per 16".Approved floor system*Nail sheathing with 8d common or galvanized box nails spaced 6" on centerat sheathing panel edges and 12" oc. in the field.#62—<strong>BRACED</strong> <strong>WALL</strong> <strong>PANELS</strong>Page 32x Pressure treated mud sill1/2" dia. anchor bolt with min. 7"embedment spaced 4'-0" on center fora two story building, 6'-0" on center fora single story building. One bolt within12" <strong>of</strong> each end <strong>of</strong> each piece <strong>of</strong> platematerial. 3"x3"x0.229" hot-dippedgalvanized plate washers are required.Approved Foundation System,Braced wall panels (BWP or ABP) must be located at each end <strong>of</strong> each braced wall line.Or, IRC Section R602.10.11 allows the braced wall panel (BWP) to be located up to 8' from the end <strong>of</strong>the braced wall line, provided there is a hold down device at the end <strong>of</strong> the BWP nearest the end <strong>of</strong> thebraced wall line. Additional options may also be available, See IRC 602.10 for more information.
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