krisway
Well-known member
What length screws do I need for 7/16" OSB on my ceiling?
Screw length
- Thread starter krisway
- Start date
Red Goat
Well-known member
While we're on the subject, is there a guide for what length screw to use for a given task? I usually just eyeball it whenever I'm building something by trying to get good penetration without having the screw pop through the other side. Am I wrong? 
toomany
Well-known member
While we're on the subject, is there a guide for what length screw to use for a given task? I usually just eyeball it whenever I'm building something by trying to get good penetration without having the screw pop through the other side. Am I wrong?
I thought the rule of thumb for bolts/screws was double the thickness you are going through. I could be wrong though.
1/2" material = 1" fastener
3/4" material = 1 1/2" fastener
Dick in Wisconsin
Well-known member
Good penetration is most important. Without good penetration nothing will hold.
Until you hit the wire in the center of the stud...
Tim The Tool Man
Well-known member
^This. Go with 1 1/2"
Where are these studs you speak of? I'll stick to what I said..
cowboy73
Well-known member
I would use 1 1/2" screws. If the ceiling joists are 24" OC, I would probably use some construction adhesive like Liquid Nails between the OSB and the joist.
Justanoldguy
Well-known member
Extreme overkill.
It won't hold any better than 1 1/2 inch
and takes more time/effort to put them in.
Why would you bother?
.............
Extreme overkill? ....That's rich..especially on this forum.
It WILL hold better than 1 1/2 inches.
Time and effort?....Guess you haven't driven many screws with an impact driver.
Why bother?..Because any extra time and cost are negligible.
Tim The Tool Man
Well-known member
Semantics. I think he meant joist. In my many years in the construction field I have seen many wires, plumbing, and gas lines run through, not over, ceiling joists. Many times it is a case where a loft/storage area exists above the ceiling. Granted the joists are usually 2x6 or 2x8 but I have seen wires run through engineered trusses as well (2x4) with a loft area above. Usually it it a do it yourself-er who runs these utilities and they simply don't have the knowledge or experience to know they should install protection plates. So I would just go with 1 1/2" screws to play it safe. The gain in strength is at best minimal and the risk of poking a utility IMHO is far greater.
BTW I will say I have yet to see a gas line run through a stud or joist that is not either black iron or gas-tite installed with a protection plate -but you never know...
djjsr
Well-known member
Screw a scrap piece of osb to a 2x4 with a 1 1/2" screw and try to pull it off. I'll bet the head of the screw will pull through the osb before you pull the screw out.
If a sheet of osb weighs 75 lbs (probably less) and you hold it with 25 screws, each screw is theoretically holding 3 lbs, right? Seems llike you don't need a very long screw to hold 3 lbs.
If a sheet of osb weighs 75 lbs (probably less) and you hold it with 25 screws, each screw is theoretically holding 3 lbs, right? Seems llike you don't need a very long screw to hold 3 lbs.
We were taught in HS industrial Arts (shop) class, you want a fastener 2-3 times the length material you're screwing/nailing through as a general rule.
If I was screwing 1/2" material I'd use a 1 1/2" fastener or 1 5/8" (more commonly found sometimes)
The 3/4" material, while the same fastenes would work, I'd probably go with a longer fastener and utilize a 2" one.
I'd rather err on a fastener that was slightly too long (of course not penetrating the far side of the work) than one that is barely long enough.
I’ve also been in the construction field for more years than I care to admit. I’m not looking to get in a ******* match over screw length.
It may be semantics..but in this case it makes a difference. Unless the ceiling joists are 2X4 in which case screwing OSB or anything else for that matter should be a mute point. I’ll give you the fact that LOTS of work done/or being done doesn’t conform to building code safety. It’s precisely having seen way too many "good enough/close enough" situations fail is the reason I will go a little above and beyond(see extreme overkill) when it comes to fasteners …or loads…and many other construction specs. I’ll also wager that in 90% of these situations, cost and time don’t play much of a factor.
If the case was screwing plywood over an already covered surface area, I’m going to assume the worst and use a fastener that is not likely to cause any damage. Unless I’m missing something, that scenario is clearly not the case here.
The OP is free to use whatever screw length he feels is adequate. He asked for opinions.. I gave mine. What I didn’t do is offer a false or unrelated excuse for dismissing someone else opinion.
My apologizes to the OP for derailing your thread. I’ll refrain from any more comments concerning this matter. Good luck with your project.
crewchief888
Well-known member
wife says longer is better...
Erampu
Well-known member
That'll work until you have to go over sheetrock. In that case you'll have to go a lot longer.
diggerrick
Well-known member
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Exactly what I would do if I knew I didn't have to take it back down for any reason.
Herb67SS
Well-known member
Then you're screwed. Sorry couldn't resist. Don't use adhesive in that case.