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A roofing system consists of a waterproof membrane, attachments, cover board (if present), insulation, and vapor or air barrier [retarder (if present)]. A roof assembly is a roof system that includes the structural deck. Wind-uplift ratings are reported by subjecting roof assembly mockups to wind dynamics. Most of the time, technical reports clearly document the properties of membranes and attachment systems (fasteners, plates, and seams) and only briefly mention the strength of the fastener-deck interface. Research by a North American roofing consortium established at the National Research Council of Canada, the Special Interest Group for Dynamic Evaluation of Roofing Systems, has demonstrated the significant influence of fastener-deck parameters on the wind-uplift resistance of mechanically attached roofs. This paper presents data and information from this ongoing investigation. Seven different roofing assemblies using three widely used roofing membranes with different fastener-deck combinations were constructed and tested under dynamic wind conditions. Assembly responses were measured based on two design factors: pressure and force. The present study identified three parameters characterizing the fastener-deck interface strength: deck grade, deck gauge, and fastener type. The study found that assemblies tested with steel decks having thicker gauge or higher yield strength tend to have greater fastener-deck strength and therefore they sustain higher wind-uplift pressures compared to assemblies with thinner gauge or lower yield-strength decks. Similarly, assemblies where the membrane attachment is made with fasteners with larger shank diameters sustained higher wind-uplift pressures compared to assemblies installed with smaller shank diameter fasteners. This study also found that fastener pullout resistance could be used as a verification factor for estimating assembly wind resistance. [ABSTRACT FROM AUTHOR]

Abstract: Air intrusion through roof assembly is a concern for wind uplift resistance and life-cycle performance of roofs. Airflow control is usually achieved by the installation of an air barrier/retarder in the roofing assembly. Even though the concept of air barrier/retarder and air barrier systems has been around for decades, it is still considered a new notion to the roofing industry. Currently, there are no widely accepted standard specifications or test methods to determine air intrusion through roofs or roof assemblies. An experimental procedure has been under development at the National Research Council of Canada to quantify the air intrusion of roof assemblies. As part of this investigation, five roofing assembly configurations were quantified for air intrusion. Relative performance of the air retarding effect of the five assemblies indicated that assemblies with air barrier/retarder had lower air intrusion rates than without. Measured air intrusion rates are compared with the existing codes of practice and standards. This comparison clearly demonstrates the significance of air intrusion into the roofing assembly and the necessity of a standardized air intrusion test method for the roofing industry. With the measured data, attempts were made to perform thermal load calculations using a simplified procedure, and through two case studies the impact of air intrusion through roofing assemblies on energy performance was estimated. [Copyright &y& Elsevier]

Roof wind design consist of three parts: determination of wind loads, evaluation of wind uplift resistance and correlating the resistance with the design load such that the resistance is higher than the load requirement. Wind uplift resistance of a system with its respective components is evaluated in laboratory testing. This paper presents a novel approach to estimate wind uplift resistance when components are substituted during field application. Wind dynamics, on a mechanically attached single-ply roofing assembly, lift the membrane and cause fluttering, introducing stresses at the attachment locations. In such assemblies, the fastener–deck interface is a critical design factor. First, by taking steel deck as a component this paper systematically characterizes the various steel decks that are commonly used in low slope application. Second component, namely the fasteners and its engagement strength with deck have been quantified for variations of its design, size and sources. Based on this component characterization, fastener pullout resistance (FPR) is identified as a verification factor for system wind resistance estimation. When variations occur in the fastener–deck interface between the proposed and the existing configurations, the present research through case studies has proved that: “as long as the FPR of the proposed configuration is higher than the existing configuration then wind uplift ratings can be maintained”. This is valid as long as both the configurations have all the remaining roofing components similar with comparable layout. Based on this verification, the study recommends that the testing lab should report the FPR along with the wind uplift resistance such that FPR can be used as a verification factor to accept design/field alternatives. [Copyright &y& Elsevier]

In North America, approximately one-fourth of low-slope buildings are roofed with a mechanically attached assembly (MAA) with a single-ply membrane. During wind suctions, the membrane can lift and billow. This creates localized suction under the membrane. If design provisions are not made to control the air intruison at the deck level, this suction pressure can draw the indoor conditioned air into the assembly. Two main factors influence the air intrusion: the air permeability of the components and shape or volume changes during the wind uplift. Available standard test procedures can quantify the former for roof materials. However, there is no widely accepted standard specification or test to address the air intrusion characteristics of roofing assemblies. Air leakage measurement techniques used for walls are also not applicable for roof assemblies due to the membrane shape and volume changes in the roof assembly. Research efforts are under way at the National Research Council of Canada to quantify the air intrusion rate of roof assemblies. This paper presents the details of the experimental setup, test procedure, and validation effort of this newly developed test method. [ABSTRACT FROM AUTHOR]