Certifying Roof Deck Constructions for Wind Resistance
An uplifting experience
Building codes often require that roof deck constructions and coverings be designed to resist design wind load pressures in accordance with structural requirements specified in the code. They also require testing of various roof constructions to specific standards. To more effectively enforce these code requirements, it is important to understand two things: the general requirements for certifying roof deck constructions for wind resistance and the markings that identify certified roof deck constructions.
Section 1504.3 of the International Building Code requires roof systems with built-up, modified bitumen, fully adhered or mechanically attached single-ply through fastened metal panel roof systems, and other types of membrane roof coverings to be tested in accordance with UL 580, UL 1897 or FM 4474. It also requires through fastened or standing seam metal panel roof systems to be tested in accordance with UL 580.
UL 580 roof deck construction certifications
Roof deck constructions Classified for uplift resistance are covered under the Roof Deck Constructions product category (TGKX) found online using the UL ProductiQTM search tool. These roof deck assemblies have been investigated for their ability to resist both external and internal pressures associated with high velocity winds. Uplift Classifications are derived from tests conducted in accordance with UL 580, the Standard for Tests for Uplift Resistance of Roof Assemblies. This test method subjects a 10 foot by 10 foot test sample to various static and oscillating air pressures to index performance under uplift loads imposed on roof decks.
The nominal static uplift pressure, oscillating uplift pressures and the maximum static uplift pressure for each Class are as shown here.
The static pressures are maintained for a 5-minute period and the oscillating pressures are applied at a 10 second frequency and are maintained for a 60-minute period for each Class. An assembly rated Class 60 has successfully withstood pressures imposed during both Class 30 and Class 60 tests. Likewise, an assembly rated Class 90 has successfully withstood pressures imposed during Class 30, Class 60 and Class 90 tests.
The UL 580 test method provides a comparative measure of uplift resistance of roof deck constructions. The test evaluates the roof deck, or the roof deck assembly and its attachment to supports, as well as the attachment of any roof covering.
Some aspects of a roof deck assembly are not evaluated using UL 580, unless specified in the construction. These elements include:
- Secondary supports such as beams, purlins, joists, bulb tees, and lateral bracing.
- Connections of the assembly to the main structural members such as girders and columns.
- Construction details along roof edges and around roof openings such as skylights and chimneys.
For many of the Constructions, the term “Fire Not Investigated” appears. This signifies that the Construction is evaluated for uplift only. However, those Constructions noted as “Fire — Classified” have been evaluated by either the large-scale fire test, or other test procedures having fire exposure conditions related to the large scale fire test described in the UL 1256, the Standard for Fire Test of Roof Deck Constructions, in addition to wind uplift. This corresponds with Section 1508.1 of the International Building Code which allows the use of above-deck thermal insulation when such insulation is covered with an approved roof covering and complies with UL 1256 when tested as an assembly. Please note that these Fire Classifications do not involve fire ratings related to surface burning characteristics, fire resistance classifications, or Class A, B, or C external fire exposure.
Many jurisdictions require that a contractor identify a roof deck construction by its UL designation (e.g. Construction No. 355 or Construction No. NM533) and to include a copy of the design specifications in the plan review package. UL permits the reproduction of designs contained in its Online Certifications Directory, subject to the limitations shown at the bottom of each design. The specifications for the assembly, materials and components described in the constructions should be carefully evaluated at the job site to verify that the roof deck constructions are built in accordance with the UL design. Code authorities should pay special attention to ensuring that materials required to be UL Classified have the appropriate ratings and Classification Marks. Many materials and components have their own dedicated UL product categories. Some key examples are Metal Rood Deck Panels(TJPV), Roof Deck Fasteners (TLSX) and Building Units (TIAR). These categories and others for materials and components used within roof deck constructions are shown in the general category for Roof Deck Construction Materials (TGYV).
Copyright © material from Issue 2, 2010, The Code Authority newsletter. This material may or may not reflect changes that have occurred since its original publication.