StrucJoist SJ-32-42-55 - Page 9

3.3 DESIGN

StrucJoist^® Residential Joists shall be designed and installed in accordance with Tables 1 through 8 and Figures 1 through 8 of this report, except that Details R4, R5, R6 and R8 of Figure 6 of this report are not applicable to joists manufactured with grade F, G or H flanges. Additionally, Detail F10 of Figure 4 is applicable only to joists designed utilizing Tables 5 and 6 of this report. Straight-line interpolation shall be permitted for intermediate depths.

Web stiffeners shall be provided at joist supports as noted in the figures and tables. For SJ-15, SJ-25 and SJ-35 I-joists, at a minimum, web stiffener material shall meet the requirements of PS-1 or PS-2 with the face grain parallel to the long axis of the stiffener. For the SJ-55 I-joists. at a minimum, web stiffener material shall be nominal 2-inch by 4-inch (51 x 102 mm) construction grade lumber.

Design properties and span tables in this report are based on covered dry conditions of use. Dry conditions of use are those environmental conditions represented by solid sawn lumber for which the moisture content is less than 16 percent.

Joist web holes shall comply with requirements indicated in Figure 1 of this report.

Where joists are arranged to comply with the repetitive member requirements noted in the applicable code, the allowable bending moment is permitted to be increased by 4 percent.

Joists located beneath bearing walls in which the walls are perpendicular to the joists shall be provided with full-depth blocking panels to transfer gravity loads above the floor system to the wall or foundation below. See Details F1, F5 and F6 of Figure 4 of this report. The maximum allowable vertical toad associated with these details is 2,000 pounds per lineal foot.

Unless specifically noted otherwise, the scope of this report is limited to the evaluation of the StrucJoist^® Residential Joists for gravity loads. Transfer and resistance of other loads from wind, seismic forces and soil is beyond the scope of this report.

Continuous lateral support of the compression flange of the joists shall be provided, such as diaphragm sheathing attached to the top flange of single-span joists. The ends of the joists shall be restrained to prevent rollover. This restraint is normally provided by diaphragm sheathing attached to the top flange and to an end wall or a shear transfer panel capable of transferring a force of 50 pounds per foot. Blocking or cross bracing with equivalent strength is permitted to be used.

Prescriptive code requirements for bridging of solid joists sawn lumber are not applicable to the StrucJoist^® Residential Joists.

Double or triple joists shall be designed using the design properties of Tables 2 through 4 of this report and, at a minimum, shall be connected as required in Figure 8 of this report. Alternatively, double joists at openings are permitted to be installed in accordance with Figure 7 of this report.

Maximum design values for nails installed perpendicular to the LVL flange glue lines shall be as provided in the 1991 edition of the National Design Specification (NDS-91) for solid sawn lumber with the following specific gravities:

Joists with birdsmouth-cut bearings as shown in Details R4, R5, R6 and R8 of Figure 6 of this report shall be limited to the spans indicated in Tables 7 and 8 of this report.

Concentrated loads in excess of 1,000 pounds, applied to the top flange of the joist, require installation of web stiffeners in accordance with Detail F-16 of Figure 4 of this report, except the gap shall be at the bottom flange.

3.4 ONE-HOUR FIRERESISTIVE CEILING ASSEMBLIES

3.4.1 The assemblies described in Sections 3.4.2 through 3.4.5 of this report achieve a one-hour fire resistance rating as roof/ceiling or floor/ceiling assemblies. Portions of the assemblies described in Sections 3.4.2 through 3.4.5 of this report installed directly above unusable crawl space are permitted to be installed without the ceiling membrane. Portions of the assemblies described in Sections 3.4.2 through 3.4.5 of this report installed directly below unusable attic space are permitted to be installed without the floor membrane.

3.4.2 Fire-resistive Assembly 1: The assembly shall consist of a single layer floor of minimum 23/32-inch-thick (18.3 mm) tongue-and-groove plywood with exterior glue, SJ-35 or SJ-55 joists spaced a maximum of 24 inches (610 mm) on center, furring channels with support clips, insulation. and a ceiling consisting of a single layer of 1/2- or 5/8- inch-thick (12.7 or 15.9 mm) United States Gypsum Company Type C FIRECODE gypsum wallboard attached to the furring channels. See Figure 9. Assembly 1 of this report.

Floor sheathing shall be installed with the long panel dimension perpendicular to the joists with the end joints staggered 4 feet (1219 mm). Sheathing shall be attached to the joists with construction adhesive and minimum 8d cement-coated sinker nails. Adhesive shall be applied in a 3/8-inch-diameter(9.5mm) bead to the top flange of joists and grooved edges of the plywood. Nails shall be spaced at a maximum of 12 inches (305 mm) on center along the joists. Minimum 1-1/2-inch-thick (38 mm), lightweight insulating concrete with perlite or vermiculite aggregate or 3/4-inch-thick (19 mm) gypsum concrete is permitted as the finished floor.

The SJ-35 or SJ-55 joists shall have nominal 2-inch by 3- inch (51 by 102 mm) flanges. Minimum joist bearing length shall be 2 inches (51 mm). Joists shall be attached at each end to the bearing plates with 10d common or box nails. Circular holes are permitted in the webs of the joists in accordance with the details noted in this report.

Furring channels formed from minimum 0.019-inch-thick (0.48 mm) galvanized steel shall be installed perpendicular to the joists and shall be spaced 1-1/2 inches (38 mm) on center from, and on each side of the gypsum wallboard end joints and 24 inches (610 mm) on center away from the wallboard end joints. The channels shall be secured to the joists with Simpson Type CSC support clips at each intersection with the joists. At channel splices, adjacent pieces shall overlap a minimum of 6 inches (152 mm) and shall be tied with a double strand of No. 18 gage SWG galvanized steel wire at each end of the overlap. Support clips shall be nailed to the side of the joist bottom flange with one 1-1/2-inch-long (38 mm) No. 11 gage nail.

Nominal 1-inch-thick (25.4 mm), minimum 6 pcf (96.1 kg/m³) USG THERMAFIBER. mineral wool batts. 48 inches (1219 mm) long with a width equal to the on-center spacing of the structural wood members, shall be installed parallel with the joists, on top of the furring channels and under the bottom flange of the joists with the sides butted against the support clips. The butted ends of the batts shall be centered over the furring channels, with the batts tightly butted at all joints.

The gypsum wallboard shall be installed with the long dimension perpendicular to the furring channels and fastened to each channel with minimum 1-inch-long (25.4 mm) Type S, self-drilling, self-tapping, 9/64-inch-diameter (3.6 mm), bugle-head steel screws. At the perimeter of the wallboard the fasteners shall be spaced 6 inches (152 mm) on center and 3/4-inch (19 mm) from the panel edges and ends. Within the field of the wallboard the fasteners shall be spaces 12 inches (305 mm) on center. End joints of the wallboard are permitted to be continuous or staggered. At butted wallboard end joints, two furring channels shall be required. For staggered wallboard end joints, the furring channels shall extend a minimum of 6 inches (152 mm) beyond each end of the joint over the adjacent boards. Paper tape shall be embedded in cementitious compound applied over the wallboard joints with edges of the compound feathered out. Exposed screw heads shall be covered with compound. As an alternate, nominal 3/32-inch- thick (2.4 mm) veneer plaster is permitted to be applied to the entire surface of the gypsum wallboard.