| MASTERSPEC - EVALUATIONS | 11/03 (R 05/05) |
The following editing instruction relates directly to specific parts of the Section Text where it is referenced by the applicable Editing Instruction No. in the editor's notes:
This Section is primarily written as a semiproprietary specification that depends on including product and manufacturer names in Part 2. If a nonproprietary specification is required, with or without naming available products, the descriptive requirements in the Section Text may need to be combined with details on the Drawings to adequately describe the conditions and types of products required to suit Project conditions.
The purpose of roof expansion assemblies is to accommodate movement in roof surfaces or between the roof and adjacent surfaces while maintaining the watertight integrity of the roofing system. The bellows-type roof expansion assembly has greater flexibility to handle different directions of movement, but the aluminum type is more durable, can stand more abuse, and offers exposed finish options.
One problem with specifying roof expansion assemblies is that although all assemblies perform the same function, each manufacturer has products of different materials or designs. An example of this difference is the various metal flanges of the bellows-type roof expansion assemblies. Manufacturers offer either galvanized steel or polymeric-encapsulated uncoated steel as the standard flange material with stainless steel, copper, sheet aluminum, or extruded aluminum as options. If flanges are completely covered or encapsulated in the roofing membrane or flashing, galvanized steel is sufficient; if flanges are exposed, a more corrosion-resistant metal may be required for aesthetic reasons. Colored flanges, for aesthetics, are also available from some manufacturers.
Mill finish is available for aluminum exposed flanges and cover plates from all manufacturers. Anodic, fluoropolymer, and other aluminum finishes are available from some manufacturers.
Metal-flanged, bellows-type roof expansion assemblies have a flexible membrane contained between metal flanges. The flexible membrane forming the bellows is a polymeric sheet supported by a closed-cell foam. Polymeric sheet materials in the Section Text include EPDM, neoprene, reinforced chlorinated polyethylene, chlorosulfonated polyethylene, and glass-reinforced PVC. Black EPDM is recommended for economy, but white EPDM is available at a premium. Black neoprene is more expensive than black EPDM and is recommended where exposure to grease or animal fats is possible.
Corrosion of metal flanges may depend on the extent to which they are exposed or embedded in or covered with roofing materials. If metals are raised above the normal "wet" plane of the roof, corrosion may not be a severe problem. Sulfur in bitumens (and in acid rain) is a major cause of corrosion.
Where the roof expansion assembly is designed to accommodate seismic activity, the joint cover must be designed to handle rapid, three-directional movement of the magnitude of the joint design.
Roof expansion assemblies designed to withstand seismic activity are available in standard joint sizes from 4 to 24 inches (100 to 600 mm). There is an increasing awareness that seismic activity (earthquakes) is not limited to the West Coast.
Fire Barriers: Consult the local building codes to determine if fire-resistance-rated roof expansion assemblies are required. Fire barriers can be added to most roof expansion assemblies to give them a fire rating. The fire-resistance rating of fire barriers is determined by testing according to ASTM E 119 or UL 2079. Roof expansion assemblies with fire barriers should comply with the joint system movement requirements without damaging or impairing the fire resistance of the fire barrier. For all practical purposes, NFPA 251, UBC Standard 7-1, and UL 263 are equivalent to the test method in ASTM E 119. Verify which test the building officials will accept and whether manufacturers of products listed in this Section have tested their systems according to the latest edition of ASTM E 119 or UL 2079.
Several basic advantages are gained through the use of factory-produced roof expansion systems. Cost savings and speed of installation are two advantages, but these are not always the most important.
Superior joint construction is a main concern for long-term waterproof performance. It is important if there are intersecting or transitioning expansion joints. Factory-produced units, prepared for joining and including corner and intersecting units, usually perform better than field-fabricated units.
Performance of bellows-type roof expansion assemblies relies heavily on the weather resistance of the bellows cover sheet, which is exposed the same as flexible sheet roofing or elastic flashing. The user must rely on the integrity of the manufacturer for part of the selection process. If the assembly cover may be subjected to oil or grease, such as from a kitchen vent, EPDM should not be used. Colored bellows covers may be available from some manufacturers. A field-applied hypalon coating may be used on neoprene or EPDM; however, because it is rarely used, it is not included in the Section Text. Staining of the coating may be a problem with some neoprenes. Recoating becomes a maintenance item.
As a rule of thumb, the roof expansion assembly cover size for normal applications should be approximately one and one-half times the nominal joint opening or bellows span at mean temperature. If accurate anticipated movements are known, sizing should be based on that information. Install the roof expansion assembly on a curb at least 8 inches (200 mm) above the roof surface at a high point to avoid interfering with roof drainage.
Locate roof expansion assemblies at building expansion-joint locations such as the following:
Roof expansion assemblies must extend through roof edges, parapets, and fasciae and be transitioned at vertical surfaces. These assemblies should be installed between the roof surface and an intersecting vertical surface that is not supporting or supported by the roof, especially non-load-bearing walls and where the building is subject to sway.
Most units specified in the Section Text are adaptable for installation at either roof-to-roof or roof-to-wall expansion joints. Bellows-type units are also adaptable for wall-to-wall expansion joints, which usually run vertically.
Lifting the joint above the roof plane is the most important recommendation that can be made; several things are accomplished. First, ice, snow, and foot traffic are less likely to damage the joint system. Second, if curbs are used, roofing can be fully completed before installing joints, thereby reducing roof traffic to a minimum during and after roof expansion assembly installation. If a parapet is at the roof perimeter, the curbs should be lower than the parapet so the roof expansion assembly will end in the inside wall expansion-joint cover; or, if no wall joint, in the wall. Avoid placing a roof expansion assembly where water will run over or through it or be trapped by it.
Area dividers may be used to divide large or irregular roof areas, to relieve the strain on the roofing membrane caused by thermal movement within the membrane. Area dividers do not replace roof expansion assemblies, which permit different building materials and areas to move independent of each other. The assemblies in the Section Text are also not principally intended to be used for this purpose. Area divider covers are typically custom fabricated from sheet metal and should be specified in Division 07 Section "Sheet Metal Flashing and Trim."
Joint Movement Evaluations: To select the right type of roof expansion assembly, evaluate the form and magnitude of anticipated movement. Of the four forms of movement, angular change (like a door swing) can usually be disregarded. Offsetting substrate planes may or may not be significant, depending on whether the structure restrains this form of joint action. Extruded-aluminum units have only a limited capability for accommodating vertical shear. All units specified, if properly installed, have a good capacity for accommodating normal joint movement, such as opening and closing from thermal expansion. All units specified can accommodate minor joint translation, but the Architect should consult the manufacturer's published literature for units that can accommodate large translations. Some degree of translation movement occurs along any expansion joint where there is differential thermal expansion. However, this movement is usually minor compared to what happens if there is a permanent shifting of construction elements due to settlement, earthquakes, long-term aging, deflection of materials, and similar changes. Reinforced sheets do not have the elastic qualities required to absorb much joint translation movement.
Exercise care to prevent the open space in the roof joint from being a source of heat loss that allows outside conditions to affect the inside conditions any more than the roof assembly does, including the roof insulation. Unless the joint contains a fire barrier, filling the vapor barrier in the joint with insulation is recommended.
The purpose of a roof expansion assembly is to close and weatherproof the gap between the structures. Where structures are subjected to movement caused by earthquakes, sizing and covering the joint become more complicated. Seismic roof expansion assemblies must be designed to applicable building codes and should be designed by a professional engineer to accommodate the extreme movement of the structures during an earthquake. Some flexible-seal types are designed to disengage from their anchoring devices when the opening exceeds the seal's capacity. The opening of the joint space is not as critical when sizing the joint as it is when the space closes because the structural elements could destroy each other.
Publication dates represent the editions on which the current Section Text is based. Standards are revised periodically, which may occur before this Section is updated again.
The following publications are useful in specifying roof expansion assemblies. Other references may be needed for design purposes.
The list of manufacturers is neither a recommendation for the companies nor an endorsement of their products. Verify manufacturers' capability to comply with indicated requirements each time the Section Text is edited.
Architectural Art Mfg., Inc. Wichita, KS (800) 835-0028; (316) 838-4291 www.archart.com Balco Metalines A Division of Balco, Inc. Wichita, KS (800) 767-0082; (316) 945-9328 www.balcousa.com BMCA Insulation Products, Inc. GAF Materials Corporation Wadsworth, OH (800) 321-2551; (330) 335-2501 www.gaf.com C/S Group Muncy, PA (800) 233-8493; (717) 546-5941 www.c-sgroup.com W. P. Hickman Company Asheville, NC (800) 892-9173; (828) 274-4000 www.wph.com Johns Manville Denver, CO (800) 654-3103; (303) 978-2000 www.jm.com JointMaster A Division of InPro Corporation Muskego, WI (800) 222-5556; (262) 679-5521 www.inprocorp.com Michael Rizza Company Boring, OR (800) 216-4602; (503) 663-2418 www.michaelrizzacollc.com MM Systems Corporation Pendergrass, GA (800) 241-3460; (706) 824-7500 www.mmsystemscorp.com Nystrom, Inc. Minneapolis, MN (800) 547-2635; (612) 781-7850 www.nystrom.com Watson Bowman Acme Corp. Amherst, NY (800) 677-4922; (716) 691-7566 www.wbacorp.com