Screw sources, types, performance, recomendations

Jim Gerken
Hello, I am about to install a exposed fastener metal roof on my garage in MN. Next year a new home will be built and same roofing products will be used again. The garage will be a tear-off, and a new layer of OSB will be added to the existing layer of OSB, to give a very sound surface and a full inch of OSB for screw holding. A layer of 30# felt goes on next, then a layer of synthetic underlayment. When the house is built the roof will be sheated with 5/8 plywood for similar screw holding. I have done about nine other exposed fastener roofs on buildings, but not on a house until this project. I am wondering if I should upgrade to a better type or brand of screw. In the past I have used the standard hex head screw with separate steel and neoprene washer. After 18 years of service, my one building appears that these screws are backing out, however I believe they were only 1 inch long screws. I have been offered these new screws (new to me anyway, I have never seen them used before) - or these:,r:0,s:0,i:83 These last ones are advertised as galvanized, but sure look yellow-ish orange color like they may be cadmium plated. I have not seen any galvanized other than the usual flat zinc color, so suspect they are mis-labeled. I like the concept of these, as the neoprene washer is buried under the concave head and not exposed to the UV. The torx heads make them difficult to drive straight, but I will pre-drill the steel roofing to solve that. Is there anything you can add concerning the screws above that are advertized as galvanized but appear to be cad plated? Are there any other alternatives that I should consider? Please include sources for anything you recommend, if possible. Is there anything to be gained in using longer screws if the length already equals or exceeds the thicknes of roff sheathing, as in this case? THANKS!!!
David Stermer
Jim, Thanks for the questions. I don't have much info on fastener coatings, but screws should be longer than the thickness of the sheathing. I normally recommend 3 full threads are exposed. This will allow the fastener to fully develop its pull-out capacity. The point of the screw contributes very little to the pull-out capacity. Regards, David Stermer

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