Vent Shaft Enclosure
USG Vent Shaft System provides a vent enclosure for vertical shafts in apartments and other types of multi-story buildings. The 2 hr. fire rating meets UL Design U529. This shaft assembly is particularly suited for structures having a number of relatively small and widely separated mechanical, service and ventilator shafts.

Good Design Practices

1 System Performance
United States Gypsum Company will provide test certification for published fire, sound and structural data covering systems designed and constructed according to its published specifications. Tests are conducted on Company products assembled to meet performance requirements of established test procedures specified by various agencies. System performance following substitution of materials or compromise in assembly design cannot be certified; failure may result under critical conditions.

2 Control Joints
Shaft wall surfaces should be isolated with control joints or other means where: (a) construction changes within the plane of the shaft wall; (b) shaft wall run exceeds 308. Ceiling-height door frames may be used as control joints, as may less-than-ceiling-height door frames if control joints extend to ceiling from both corners. Location of control joints is the responsibility of the design professional/architect.

3 Penetrations
Penetrations of the diaphragm, such as door frames and duct openings, require additional reinforcement at corners to distribute concentrated stresses if a control joint is not used. Penetrations greater than 48" wide require supplemental support for the shaft wall at the opening. Where access panels or large duct penetrations occur in shafts having pressure loads, headers, sills and adjacent channels may require reinforcing to properly distribute these loads.

4 Pressure Loads
Where shaft walls enclose elevator and return air vents, and intermittent pressures up to 15 psf are expected, sealant is recommended at intersections with floors, ceilings, columns, ducts, etc. to seal peripheries and penetrations and minimize whistling and dirt accumulation due to air movement. Shaft walls may be used for air handling with sustained pressures up to 10 psf. Sealant selection including joint treatment, surface coatings and details to seal the wall under these sustained pressures must be provided by the designer. When air pressure exceeds 10 psf, the air handling should be contained with a metal duct.

5 Screws
Type S Screws are suitable for gypsum panel or gypsum base attachment to 25, 22 and 20 ga. steel studs. Type S-12 screws should be specified for other applications to steel heavier than 20 ga. Screw lengths should be 1" for base layer and 1-5/8" for face layer and at least 3/8" longer than the total thickness for other applications.

6 Steel Frame Construction
Runners and studs attached to beams and columns should be installed before steel is spray-fireproofed. Excess fireproofing should be removed from runners and studs before installing shaft wall liner and sealant.