USG Cavity Shaft Wall Systems
D Fire-Rated 2-Hour Assembly: UL Design U492—Install framing system and SHEETROCK brand Gypsum Liner Panels as described above using
minimum 400CH25 studs and related accessories. Friction fit min. 3" THERMAFIBER SAFB (required) in stud cavity. Apply 3/4" thick
SHEETROCK brand Gypsum Panels, ULTRACODE Core, vertically with wrapped edges parallel to and fully supported by steel framing.
Attach panels using 1-1/4" long (Type S) (Type S-12) drywall screws spaced 8" o.c. along panel edges and ends and 12" o.c. along
intermediate framing.
E Fire-Rated 3-Hour Assembly: UL Design U408—For 3 hr. assembly, erect steel runners, steel studs and liner panels as described in
section A, then continue construction as follows:
Install three layers of SHEETROCK brand Gypsum Panels, 3/4" ULTRACODE Core. Apply first and second (inner) layers vertically or
horizontally over steel studs. When applied vertically, center joints over studs and stagger min. 24"; otherwise, stagger joints min. 12".
Secure first layer to studs with 1-1/4" Type S self-drilling, self-tapping bugle-head steel screws spaced 12" o.c. Apply third layer vertically
over furring channels with 1-1/4" Type S self-drilling self-tapping bugle-head steel screws spaced 12" o.c. Finish joints with paper tape and
joint compound.
F Fire-Rated 4 hr. Assembly: UL Design U408—For 4 hr. assembly, erect steel runners, steel studs and liner panels as described in section A, then
continue construction as follows:
Install four layers of SHEETROCK brand Gypsum Panels, 3/4" ULTRACODE Core. Apply first and second (inner) layers vertically or
horizontally over steel studs. When applied vertically, center joints over studs and stagger min. 24"; otherwise, stagger joints min. 12".
Secure first layer to studs with 1-1/4" Type S self-drilling, self-tapping bugle-head steel screws spaced 12" o.c. Apply third layer vertically
over furring channels with 1-1/4" Type S self-drilling self-tapping bugle-head steel screws spaced 12" o.c. Apply fourth layer vertically or
horizontally, with 2-1/4" Type S self-drilling self-tapping bugle-head steel screws spaced 12" o.c. When applied vertically, stagger joints min.
24" from third layer; otherwise, stagger all joints min 12". Finish joints with paper tape and joint compound.
G Vent Shaft Enclosure—Install 1" x 2" x 25 ga. galvanized steel angles as runners on floor, ceilings, and partition ends. Fasten runners or angles securely
to structure with suitable fasteners 24" o.c. max.
Install 1/2" SHEETROCK brand Gypsum Panels, Firecode C Core, vertically. Fasten to angles with 1" Type S screws 12" o.c. Apply
SHEETROCK Setting-Type (DURABOND) or Lightweight Setting-Type (Easy Sand) Joint Compound on back side of liner panel and
sheet-laminate to shaft-side board with vertical joints offset 12" from inner board joints. Also screw to shaft side board with 1-1/2" long Type
G screws 24" o.c. in both directions.
Laminate face board to liner panels. Install face boards vertically with joints offset 12" from liner panel joints. Apply pressure when placing
boards to ensure good adhesive bond and fasten to liner panel with 1-1/2" Type G screws, 24" o.c.
After all attachments are made, wipe off any adhesive forced out at joints and edges. Caulk perimeter of face panels with SHEETROCK
Acoustical Sealant to prevent air infiltration.
3.2 Accessory Application
A Gypsum Panel Joints—Finish all face layer joints and internal angles with a United States Gypsum Company Joint System installed according to
manufacturer’s directions. Spot exposed fasteners on face layers and finish corner bead, control joints and trim as required, with at least
three coats of joint compound, feathered out onto panel faces and sanded smooth.
B Corner Bead—Reinforce all vertical and horizontal exterior corners with Dur-A-Bead Corner Bead fastened with clinch-on tool or staples 9" o.c. on both
flanges along entire length of bead.
C Metal Trim—Where shaft wall terminates against masonry or other dissimilar material, apply metal trim over face layer edge and fasten with screws or
staples spaced "" o.c.
D Screws—Power-drive at least 3/8" from edges or ends of gypsum panels to provide uniform dimple 1/32" deep. In gypsum base, set flush with surface
without tearing face paper.
E Control Joints—Break panels behind joint. Apply acoustical sealant to fill gap and attach control joint to face layer with staples spaced 6" o.c. on both
flanges along entire length of joint.
Metric Conversion
The table that follows provides metric equivalents for the dimensions of U.S. Gypsum Company products. "Soft" conversions merely apply a
conversion factor that translates feet and inches (according to which the products were manufactured) into metric units; "hard" metric
measurements are given for products actually manufactured in metric sizes.
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