“Roof design” is a powerful concept that is often misunderstood, misrepresented, or applied incorrectly in today’s industry. When it comes to roof design, the big question is, “Who is responsible for the roof design, or who is the responsible party?”
Determining wind uplift pressure resistance for roof assemblies is a requirement of the International Building Code (IBC)1 that is applicable to most structures located in the United States. In the 2018 edition of IBC, important specifications are found in Chapter 16, Structural Design. Section 1609 defines the requirements for wind loads, and paragraph 1609.1.1 states, “Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 30 of ASCE 7.” Additionally, IBC Section 1609.5 states, “Roof systems shall be designed and constructed in accordance with Sections 1609.5.1 through 1609.5.3, as applicable,” and Section 1609.5.1 specifies, “The roof deck shall be designed to withstand the wind pressures determined in accordance with ASCE 7.” ASCE 7 is the American Society of Civil Engineers’ Minimum Design Loads and Associated Criteria for Buildings and Other Structures.2 Note that governing entities have adopted various versions of IBC and ASCE; however, the same general principles remain constant.
In IBC Chapter 15, Roof Coverings, the performance requirements for roofing are outlined in Section 1504, Performance Requirements. Paragraph 1504.1 specifies, “Roof decks and roof coverings shall be designed for wind loads in accordance with Chapter 16 and Sections 1504.2, 1504.3, and 1504.4.” Section 1504.3, Wind Resistance of Non-ballasted Roofs, states,
Roof coverings installed on roofs in accordance with Section 1507 that are mechanically attached or adhered to the roof deck shall be designed to resist the design wind load pressures for components and cladding in accordance with Section 1609.5.2. The wind load on the roof covering shall be permitted to be determined using allowable stress design.