In Hawaii, we have a lot of steel-framed buildings with z-bar steel purlins supporting the metal roof. My attachment means of choice is using T-5 screws (#12 x 24 threads per inch). These buggers are self-drillers with a carbon steel shank and drill point and stainless steel hex head cap with rubber grommet. With a screw gun, you can actually zip these puppies through your Pro Solar rail, through the roof metal and through the z-bar purlin without the need to pre-drill. I use two screws per attachment point. I've had this method studied by licensed structural engineer and he has given me the thumbs up. Between the rail and the roof metal, I use a 2" square by 1/4" thick piece of Hypalon rubber to act as a dielectric between the al. rail and steel roof.
I get the T-5 screws from Dynamic Fasteners and the Hypalon rubber strips from MacMaster-Carr. Marco ProVision --- You wrote: We did four 6.8 kW systems for a commercial development with standard metal building constructions. This building too had purlins 5' o.c. running parallel to the ridge. After looking into it, we determined that #14 Tek screws worked fine. The blow-mind was something around 1,400 pounds of pull-out strength in the steel we were using (it varies with the gauge of the purlin steel) per screw. (This is from memory and may be off.) We used a single Tek screw per L-foot, with a 2" square of sealing bitumen membrane under each foot, plus caulk after setting the screws. Test your "red" steel for workability. Try to drill holes in an accessible spot. See if this might work for you. Allan Sindelar _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
