Metal Construction News, February 2019

KNOW YOUR PRODUCTS Insulated Metal Panels Used for Low Slope Roof Projects By William Lowery Roofing IMPs are a strong building module with value For years insulated metal panels IMPs have been used for non load bearing exterior wall partition and roof panels for projects that required claddings to meet standard design loads including wind and deflection resistance However the very nature of combining components in this case a semi rigid urethane core and light gauge steel facings into a composite creates a much stronger building module In this case the sum of the components far exceeds the limited physical properties of each Many traditional low slope roof deck assemblies require products to meet not only resistance to wind and deflection standards but diaphragm shear resistance values as well Over the last few years several leading IMP manufacturers through their research and development teams embarked on physical testing to see what diaphragm shear resistance levels could be achieved and then compare the results to typical steel deck assemblies Not surprisingly the results of initial testing showed IMPs performed extremely well Subsequent testing at higher loads and with various external gauges of steel and fastening combinations established the data needed to publish diaphragm resistance tables for roof decking When it came to practical use earlier efforts to push IMPs into the U S low slope roof market gained little traction because they included complete assemblies That is the roof deck arrived at the job site with the membrane pre adhered In concept it might have made a lot of sense but without the ability to use exterior fasteners through the composite deck there was no way to achieve diaphragm shear resistance Furthermore the width limits on the panels required too many seams prompting concerns about leakage Nonetheless an IMP roof deck combined with a membrane remained rich in obvious benefits over traditional steel deck based assemblies Initial installations of IMP roof deck panels and a field applied membrane have revealed these advantages Installation IMP roof deck installations eliminate the layering staggering and then fastening of roof insulation fiberboards to the B deck a time consuming costly step Also an IMP roof deck can be installed in rain and serves as a far superior substrate Strength Not only is an IMP roof deck highly resistant to damage during and after installation but the deflection resistance transverse load is also superior to traditional assemblies Better insulation Because the semi rigid urethane core is encapsulated with impermeable steel facings it provides R values of approximately 8 per inch of thickness at 40 F mean temperature This means a thinner monolithic roof assembly requiring less roof edge trim Versatile substrate Wind uplift testing has been completed for both mechanically attached and field adhered Thermoplastic Polyolefin TPO and Polyvinyl Chloride PVC single ply membranes The former attach into the exterior primed steel substrate only and not through the entire composite panel preventing leakage White interior finish IMP roof decks are supplied as a standard with a nominal 10 ml embossed white polyester factory applied high heat paint finish that will lower interior lighting requirements Fewer fasteners For assemblies requiring diaphragm shear resistance IMP deck panels are attached to the secondary steel supports using lowprofile deck style fasteners similar to those used to attach both the roof insulation board layers and the single ply membrane with far fewer fasteners For assemblies not requiring diaphragm shear resistance IMP deck panels can be attached via hidden joint fastening In either case the primed steel substrate is ready for installation of the single ply membrane Also the Induction Welding Technology with the All Weather Insulated Panels OneDek system will provide further installation efficiencies Membrane Membranes tested and approved in combination with IMP roof decks include 60 ml white TPO and PVC the white being preferred for lower carbon footprint Speed IMP roof deck panel assembly should allow for a building to be dried in much faster than traditional field assembled roof assemblies and can easily be applied in sections allowing for greater flexibility in construction scheduling Easy to reroof At some point when the singleply membrane needs to be replaced IMP roof deck panels will continue to perform as the insulated substrate The roof remains intact during repair If an original membrane has been fully adhered a new mechanically attached membrane can be installed over it If the old membrane was mechanically attached it can easily be removed and replaced These significant savings cannot be assumed by owners of buildings with traditional roof assemblies Warranty Because the complete roof assembly inclusive of the deck is tested and available under single brands a 20 year top to bottom warranty is available from the manufacturer The savings achieved during installation add to the value of roofing with IMP products But theres something even more important to contractors and building owners IMPs bring peace of mind by increasing the chances of a project coming in on time and on budget William Lowery is president of All Weather Insulated Panels Vacaville Calif To learn more about IMP roof deck products go to www awipanels com onedek list or email sales@ awipanels com 30 METAL CONSTRUCTION NEWS February 2019