Screw Type for 7/16 OSB decking

Guest User
10/23/2014
Hi there, I have a metal roof over 7/16 OSB decking and it unfortunately has #9 screws that are coming loose. I am planning to have them replaced with #14 Mill Point screws, but am confused about the difference between 'Type A' and 'Type AB'. Questions: 1. Would either 'Type A' or 'Type AB' work OK in this application? I see that 'Type A' has a more aggressive thread, so probably good for OSB, but so far I've only found 'Type AB' that can match the existing color so may be stuck with that. 2. I've read some suggestions about putting a bit of urethane (NP1?) into the screw hole to help hold the screw better. Would this be a reasonable thing to do to better ensure that the screws won't back out? What about using an elastomeric, such as Sashco's "Through The Roof"? Thanks so much!
David Stermer
10/23/2014
Hi James, Thanks for your question about metal roofing. Type A and Type AB points are very similar. Type A are generally intended for lighter gage applications, though there is quite a bit of overlap in the range of their applicability. Both Type A and Type AB should be fine for your application. A bit of urethane sounds like a good idea to me to help the new fasteners get a grip on the wood. I would recommend inspecting the wood deck (either by pulling up panels while replacing fasteners or viewing from the underside) to confirm it has not deteriorated and lost is ability to support the metal panels. Regards, David
Guest User
10/23/2014
Thanks very much for the quick response! Much appreciated. Take care....
Guest User
11/14/2014
Hello again, I hired a roofer to do the rescrew with #14 ZAC screws (it's a two level roof with 5/6 and 6/6 pitch) and his sloppy crew messed up here and there by over-tightening and breaking the gasket. In some cases the screw looks okay, but half of the gasket is missing underneath. A number of times they removed a screw and didn't replace it with anything. I discovered this by using binoculars from the ground, or looking out the 2nd story window (I can't see the top level roof very well). The owner of the roofing company came by yesterday and spent 2 hours personally replacing any obviously bad screws on both roof levels. He does good work - the crew he used - not so much. The roofing company owner thinks that the roof will be okay now, but I'm not so sure. Question: I suggested that the owner personally (with 2 of his best guys - not the ones that worked the roof) replace all the screws with new #14 screws to make sure they are properly set and not under- or over-tightened. He thinks this might cause problems because the screws might not get as good of a grip the second time, and that I definitely don't want to move up to the next largest screw. Would it be wise to have all the screws replaced, or wait and see what happens? My area gets winter snows & summer monsoonal rains with anywhere from 25" to 35" of annual rainfall. I don't know how long it will take for a leak to physically reveal itself in the house. I'm inclined to ask him to go ahead and personally replace all screws just for peace of mind. Thanks for any advice or insight.
David Stermer
11/14/2014
Hi James, I would not recommend replacing all the screws just for peace of mind. Screws that are functioning fine really cannot be improved upon. I would only recommend using the larger screws for holes that are stripped out. Otherwise, the standard screw is the right solution. Regards, David

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