Wind Uplift Pressures on Low-Slope Roofs (Updated 2018)

The fourth (2018) edition of this monograph is a publication of the RCI Foundation and has been authored by Stephen Patterson, RRC, PE, of Roof Technical Services, Inc. and Madan Mehta, PE, PhD of the University of Texas at Arlington.

The monograph is keyed to the latest edition of the ASCE/SEI publication: Minimum Design Loads and Associated Criteria for Buildings and Other Structures, commonly known as the ASCE 7-16 Standard. It consolidates all provisions of ASCE 7-16 that are applicable to low-slope roofs in a single document with an aim to help roof consultants, architects, and engineers design a wind-resistant low-slope roof. Similar to its earlier editions, the fourth edition covers wind pressures on low-slope roofs at different levels of details to suit a diverse body of readers.

Curious readers will appreciate the theoretical description of the dynamics of wind flow around buildings and its effect on wind pressures on low-slope roofs. A step-by-step procedure for determining wind uplift pressures on low-slope roofs, followed by numerical examples of how to use the procedure, provides clarity to theoretical description. A set of tables have been provided from which wind pressure values can be simply selected without the use of any procedure or calculations. 

The update in the monograph was necessitated because of several changes made in ASCE 7-16 from its earlier ASCE 7-10 Standard. A few of the important changes in ASCE 7-16 that impact the design of low-slope roofs and explained in the monograph are:

• A basic wind speed map for Risk Category IV buildings has been added. In ASCE 7-10, Risk Categories III and IV were lumped together, providing one map for both categories. The two categories have been separated in ASCE 7-16.
• Significant changes in basic wind speeds for the continental U.S. and Alaska have been included. Consequently, the land masses under both hurricane-prone and non-hurricane-prone regions of the U.S. have changed.  
• New effective wind speed maps for the islands of Hawaii have been added.
• A (new) ground elevation factor that accounts for a location’s elevation above sea level has been added.
• A (new) building enclosure classification has been introduced.
• Roof zones for roof height ≤ 60 ft. have been modified substantially.

This popular publication deserves to be a part of your personal library if you deal with roofing and building envelope design and/or forensics.

Authors: Stephen L. Patterson, P.E., RRC, and Madan Mehta, P.E., Ph.D.