The Roof Strengthening Benefits of Strong Sub-Purlin

By Dale Nelson, Roof Hugger. 

Add capacity to existing metal building roof framing with Roof Hugger Sub-Purlins. 

Roof Hugger Sub-Purlins are proven through first-of-its-kind testing, to increase capacity to already existing purlin systems in metal buildings. The testing was conducted on a retrofit framing system over continuous purlins and the results are significant. 

Roof Hugger recently conducted 24 Gravity Base Tests using varying height, 14 and 16-gauge Roof Hugger Sub-Purlins over 12 and 16 gauge 8” purlins, mounted to simulate 2 - 25’-0” bay spaces. The test chamber was a full 8’ wide x 51’ long and had multiple sensors and video camera stations recording the testing. 

Base testing is most commonly done using simple span purlins with 1-25’-0” span. 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, Florida to confirm the actual performance of standing seam roofs in actual Hurricane conditions. 

Force was contracted to design and construct a 50’ 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 amazing, showing that in some cases the Roof Hugger sub-purlins could add from 13% to over 70% in additional capacity to an older buildings purlin design depending on the Huggers used and certain existing conditions. 

The testing confirmed what Roof Hugger had been hearing from our 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 two pounds per square foot. The current International Building Code for Existing Buildings allows for an extra three pounds per square foot 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 past its original design. 

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. 

Roof Hugger continues to be the leader in retrofit testing for the metal over metal reroofing market.  Visit our new website at www.roofhugger.com or give us a call at 800-771-1711 to discuss your retrofit needs. 

Learn more about Roof Hugger in their RoofersCoffeeShop® Directory.  

Original article source: Roof Hugger