New Testing Shows Roof Hugger Sub-Purlins Can Add Capacity To Older Buildings' Purlin Design

Odessa, FL - In the first of its kind testing of a retrofit framing system, over continuous span purlins, Roof Hugger Sub-purlins have again demonstrated to add capacity to an existing metal building roof purlin system.

Roof Hugger recently conducted 24 Gravity Base Tests using varying height, 14- and 16-gauge Roof Hugger Sub-purlins over 12- and 16-gauge by 8-inch deep purlins, mounted to simulate two 25’-0” bay spaces. The test chamber was a full 8’-0" wide x 51’ -0" long with multiple sensors and video camera stations recording the testing.

Base testing is most commonly done using simple span purlins with one 25’-0” span, as was conducted in earlier tests going back to 2009. However, Roof Hugger wanted more real-world performance testing and so commissioned Force Engineering and Testing of Humble, TX to build a 50’ test chamber to conduct these tests.

Force Engineering, no stranger to unusual test assemblies, was also the firm that designed and constructed a 155-mph test building for the Florida International Universities’, Wall of Wind, wind tunnel test facility in Miami, FL to confirm the actual performance of standing seam roofs in actual Hurricane conditions.

Force was contracted to design and construct the larger test chamber and over a period of several months conducted this critical testing of the Roof Hugger Sub-Framing system to see if they did actually add strength to the existing buildings purlin.

The test results were impressive, showing that in some cases the Roof Hugger Sub-purlins could add from 13% to over 70% in additional capacity to an older building's purlin design depending on the Huggers used and certain existing conditions.

The testing confirmed what Roof Hugger had been hearing from its many contractors/erectors in the field - that buildings felt much stiffer and tighter after they were retrofitted with Roof Hugger Sub-purlins.

A typical metal-over-metal retrofit adds about 2 lbs./sq. ft. The current International Building Code for Existing Buildings allows for an extra 3 lbs./sq. ft. to be added when retrofitting a building, but many older metal buildings have been modified over the years with additional equipment, lights and mechanical systems pushing the old framing beyond its original design.

It was noted that some public works, schools, military or other high importance project designers also want confirmation that the existing building can tolerate the additional load of retrofitting the old roof system. Some want to see if they can recover lost capacity due to building modifications.

About Roof Hugger

Roof Hugger notched sub-purlins enable replacement of new metal roof panels over an old metal roof. They can be used over screw-down or standing seam roof systems and can accommodate new standing seam or screw-down panels. Roof Huggers also maintain integrity of original design loadings; achieve "thermal break" air space between old and new roof sheets; allow for optional insulation; and are laboratory and load tested—with certified load charts. For more information on metal-over-metal retrofit re-roofing, contact Roof Hugger at 800-771-1711 or visit www.roofhugger.com.