A roof structure is made stronger by the system elements working together—much stronger than its main load-bearing element, the rafter, is alone. Current engineering analysis methods do not take this composite action into account when evaluating rooftop strength.

A roof structure is made stronger by the system elements working together—much stronger than its main load-bearing element, the rafter, is alone. Current engineering analysis methods do not take this composite action into account when evaluating rooftop strength.

Results from the Sandia research reports, “Structural Code Considerations of Solar Rooftop Installations” and “Empirically Derived Strength of Residential Roof Structure for Solar Installations,” will be featured in an upcoming webinar hosted by the Solar Instructor Training Network (SITN). Sandia PI Stephen Dwyer (in Sandia’s Geotechnology & Engineering Dept.) will discuss implications of the report for solar installers.

The webinar is scheduled for 2 p.m. (EDT) on Tuesday, September 22. The event is free, but registration is required. SITN is funded by DOE’s SunShot Initiative and managed by the Interstate Renewable Energy Council.

Sandia tested numerous rooftop structure configurations at UNM’s structures laboratory.

Sandia tested numerous rooftop structure configurations at UNM’s structures laboratory.

The reports detail research conducted by Sandia and funded by the DOE’s SunShot Initiative to test numerous wood rooftop structures to failure and compare actual rooftop load-bearing capacity data to the perceived load-bearing capacity in building. Results indicate that rooftop load-bearing capacity is higher than allowable loads as defined by the International Residential Code (2009).