I'm about ready to hang sheetrock, but I want to be certain I get the correct length of screws. This post has almost the complete answer I'm looking for: http://www.johnlsayers.com/phpBB2/viewtopic.php?p=20003
... but not quite everything I need or not quite to the specs that my room will be.
I'll have two layers of 5/8" sheetrock. What length of screw do I need for the first layer, and what length do I need for the 2nd? I asked the kids at Home Depot this question and they looked at me like I was nuts - like 2 layers of sheetrock is for crazy people.
Screw length for 2-layer drywall installation
Originally posted at johnlsayers.com, topic 7927.
Well for my beef up layers..on the walls (not ceilings) i used 1"1/4 first layer into the 7/16 osb...then used a 2" screw for second layer gypsum. I'm doing 2 layers of 5/8 gypsum between studs over 0SB. Under my OSB is a 1/2 compressed fiberglass so the screws could punch through the OSB a bit if i went a bit too deep. Everything is holding together like Fort Knox so far. This may be the room i run to in the event of an earthquake!
For beef-up: Using cleats screwed to the sides of the studs holds the drywall firmly in place. Using some screws into the OSB is good to get a temporary hold, but drywall screwed only to OSB is no good I think... :roll: Sorry, n8not9it, but the method you described isn't kosher in my opinion. :(
kindohm, for your first layer of 5/8" gypsum wallboard, assuming there's no RC or anything between the studs and drywall, and assuming wood framing, you'll want to use 2" coarse thread drywall screws so that you get 1 3/8" penetration into the studs and joists. For your second layer of 5/8" gypsum wallboard, you'll need 2 1/2" coarse thread drywall screws so that you get 1 1/4" (the bare minimum) penetration into the studs and joists.
Fine thread screws are for steel framing... And in that case I think you can get away with a little less penetration. You didn't say what kind of framing you're using... I assume timber, but I'm including the steel info for the benefit of others who may be using steel.
Of course, I'm going to highly recommend that you check with your local building department on the screw schedule you need to be using in accordance with the model codes that are in effect in your jurisdiction... I wouldn't be me if I didn't. 8) And never EVER rely on Home Depot or any supplier to provide code advice. Their word means nothing! ;-)
I realize there are posts in the forum here that suggest using fewer screws on your first layer, but my building department gave me an adamant "NO" to that idea... And in subsequent discussions here and learning more about the role that screws play in holding drywall in the "not crashing down" position, I can't help but to agree with my local authority.
Hope that helps...
--Keith :mrgreen:
Not trying to be arguementative for arguement sake, but how is it inadequate to fasten the wall gypsum to the OSB (OSB which is cleated securely -review my cavity filling thread) with 1 1/4" screws through first layer of 5/8" gypsum? 1 1/4" is 2x 5/8" so i am over penetrating into the 7/16 OSB by about 1/4". Thats sounds like more than enough fastening depth. The completed two layers of 5/8" plus 7/16" OSB gives me 1 3/4" of wall thickness which my final 2" screw penetrates completely through by another 1/4"?? Reading through your second paragraph leads me to think you are speaking about a different sort of beef up situation because if i used a 2 1/2" screw through the 1 3/4" of beefed up wall would penetrate through all layers and directly into the exteriorstucco (if you could screw into it at all) leaving an exposed head.For beef-up: Using cleats screwed to the sides of the studs holds the drywall firmly in place. Using some screws into the OSB is good to get a temporary hold, but drywall screwed only to OSB is no good I think... :roll: Sorry, n8not9it, but the method you described isn't kosher in my opinion. :( kindohm, for your first layer of 5/8" gypsum wallboard, assuming there's no RC or anything between the studs and drywall, and assuming wood framing, you'll want to use 2" coarse thread drywall screws so that you get 1 3/8" penetration into the studs and joists. For your second layer of 5/8" gypsum wallboard, you'll need 2 1/2" coarse thread drywall screws so that you get 1 1/4" (the bare minimum) penetration into the studs and joists. Fine thread screws are for steel framing... And in that case I think you can get away with a little less penetration. You didn't say what kind of framing you're using... I assume timber, but I'm including the steel info for the benefit of others who may be using steel. Of course, I'm going to highly recommend that you check with your local building department on the screw schedule you need to be using in accordance with the model codes that are in effect in your jurisdiction... I wouldn't be me if I didn't. 8) And never EVER rely on Home Depot or any supplier to provide code advice. Their word means nothing! ;-) I realize there are posts in the forum here that suggest using fewer screws on your first layer, but my building department gave me an adamant "NO" to that idea... And in subsequent discussions here and learning more about the role that screws play in holding drywall in the "not crashing down" position, I can't help but to agree with my local authority. Hope that helps... --Keith :mrgreen:
I just reviewed your thread, but you don't cover the beef-up strips of drywall yet. :roll:. . . how is it inadequate to fasten the wall gypsum to the OSB (OSB which is cleated securely -review my cavity filling thread) . . .
My 1 1/4" "bare minimum" of penetration remark was based on a recommendation from Rod Gervais. In fact, upon reviewing his comments, I see that he actually said 1 3/8" was "absolute minimum." Simply put, it's impossible to get more than 7/16" penetration in 7/16" OSB. :( I'm sure the pull-out resistance of screws in OSB is inferior to that of solid studs or joists, especially when there is greater penetration on the timber framing than on the OSB.. . . with 1 1/4" screws through first layer of 5/8" gypsum? 1 1/4" is 2x 5/8" so i am over penetrating into the 7/16 OSB by about 1/4". Thats sounds like more than enough fastening depth.
No, I understand that... I'm not suggesting you used screws that were too short. I'm am saying that when you have such constraints (which are common), you have to get creative to come up with a solution that will meet or exceed resistance of the forces that the standards are engineered for. In your case, n8nod9it, since you're not framing your inner leaf yet, you should be able to install a second layer of cleats. Granted, in my research this evening in responding to this thread, I did find several references to the appropriateness of using 1 1/4" screws to hang 1/2" drywall and 1 5/8" screws to hang 5/8" drywall (single layers, of course). Those recommendations yield 3/4" and 1" of penetration, respectively, and those recommendations are more lenient than Rod's 1 3/8" "absolute minimum." (In any case, 3/4" and 1" is greater than 7/16".) In my book, when there's a dispute between standard/acceptable practice and Rod's recommendation, where Rod's recommendation is stricter and more conservative (and it often is), Rod wins. 8) Have you bought Rod's book yet? If not, you should -- it's awesome. You'll find that it's worth every penny, and lots more.Reading through your second paragraph leads me to think you are speaking about a different sort of beef up situation because if i used a 2 1/2" screw through the 1 3/4" of beefed up wall would penetrate through all layers and directly into the exteriorstucco (if you could screw into it at all) leaving an exposed head.
No worries. :D I always welcome the challenge. Sometimes I'm wrong, and when proven so, I'm good at eating my words. Sometimes they're quite tasty... Especially when Rod himself serves them up for me. ;-) --Keith :mrgreen:Not trying to be arguementative for arguement sake . . .
I have some new pics i will be adding soon of the gypsum layers.I just reviewed your thread, but you don't cover the beef-up strips of drywall yet. :roll:. . . how is it inadequate to fasten the wall gypsum to the OSB (OSB which is cleated securely -review my cavity filling thread) . . .
I have the 1/2 compressed fiberglass behind the 7/16 OSB to even out the irregularities in the stucco walls, so thats where i get a bit of over penetration. I read over your thread and it seems both you and Rod are speaking about *ceiling* hanging of drywall on RC through 2 layers 5/8" gypsumand minimum screw penetration depths of 1 3/8... Am i lost? Do i need less coffee? More coffee? Cuz i didn't mean to imply those inferior penetrations to be meant for ceilings...but wallsMy 1 1/4" "bare minimum" of penetration remark was based on a recommendation from Rod Gervais. In fact, upon reviewing his comments, I see that he actually said 1 3/8" was "absolute minimum." Simply put, it's impossible to get more than 7/16" penetration in 7/16" OSB. :(. . . with 1 1/4" screws through first layer of 5/8" gypsum? 1 1/4" is 2x 5/8" so i am over penetrating into the 7/16 OSB by about 1/4". Thats sounds like more than enough fastening depth.
Agreed. OSB has a far weaker pullout of certain hardwoods as its inherent integrity is much less dense and uniform than natural wood.I'm sure the pull-out resistance of screws in OSB is inferior to that of solid studs or joists, especially when there is greater penetration on the timber framing than on the OSB.
Where would the second layer of cleats be needed? On the face of the exterior studs overlapping the 2nd layer of gypsum on all of the exterior bay studs??? Like this? http://www.johnlsayers.com/phpBB2/files ... p2_263.jpgNo, I understand that... I'm not suggesting you used screws that were too short. I'm am saying that when you have such constraints (which are common), you have to get creative to come up with a solution that will meet or exceed resistance of the forces that the standards are engineered for. In your case, n8nod9it, since you're not framing your inner leaf yet, you should be able to install a second layer of cleats.Reading through your second paragraph leads me to think you are speaking about a different sort of beef up situation because if i used a 2 1/2" screw through the 1 3/4" of beefed up wall would penetrate through all layers and directly into the exteriorstucco (if you could screw into it at all) leaving an exposed head.
:( Edit: Fixed quoting. --KeithGranted, in my research this evening in responding to this thread, I did find several references to the appropriateness of using 1 1/4" screws to hang 1/2" drywall and 1 5/8" screws to hang 5/8" drywall (single layers, of course). Those recommendations yield 3/4" and 1" of penetration, respectively, and those recommendations are more lenient than Rod's 1 3/8" "absolute minimum." (In any case, 3/4" and 1" is greater than 7/16".) In my book, when there's a dispute between standard/acceptable practice and Rod's recommendation, where Rod's recommendation is stricter and more conservative (and it often is), Rod wins. 8) Have you bought Rod's book yet? If not, you should -- it's awesome. You'll find that it's worth every penny, and lots more.No worries. :D I always welcome the challenge. Sometimes I'm wrong, and when proven so, I'm good at eating my words. Sometimes they're quite tasty... Especially when Rod himself serves them up for me. ;-) --Keith :mrgreen:Not trying to be arguementative for arguement sake . . .
I just realized this sounded like i was speaking about inner leaf construction of wall buildup and not between stud bays of exterior construction which i was.Well for my beef up layers..on the walls (not ceilings) i used 1"1/4 first layer into the 7/16 osb...then used a 2" screw for second layer gypsum. I'm doing 2 layers of 5/8 gypsum between studs over 0SB. Under my OSB is a 1/2 compressed fiberglass so the screws could punch through the OSB a bit if i went a bit too deep. Everything is holding together like Fort Knox so far. This may be the room i run to in the event of an earthquake!
No, I understand you were referring to outer leaf beef-up.
Yes, that image you linked to is similar to what I had in mind... Although I don't actually use or recommend that specific configuration to folks because, in my case, I didn't actually do it. Steve (knightfly) said I didn't need to do so, since I was driving the screws diagonally into the studs.
I realize you're talking about walls and not ceilings. Certainly, the risk of pullout is far greater overhead than it is on walls.
I may be overreacting, but I'd rather overreact than underreact.
I'll defer to whatever your local building department says is OK. :)
--Keith :mrgreen:
Thanks guys.
I'm using wood framing. There is no RC on the walls, but I'm using RC-1 on the ceiling. I totally forgot to mention that. Is there anything special about the screws for the RC-1 on the ceiling?
Also, how difficult is it to screw into RC-1? I tried screwing into a plain, bare piece of RC-1 a while back and it was HARD. ??? Is there a trick to making it easier?
For RC, you use the same fine thread screws designed for steel framing - they should be self-drilling types. You just hold the screw gun against the material (spinning, of course) til the screw bites into the metal and pulls up tight.
If you keep a good pressure on the screw gun with your hand until the screw is properly sunk into the drywall, it doesn't make the screw threads do ALL the work of pulling the screw tight; this takes a bit of practice, you will probably want to play with some scraps first.
Remember, RC is a "spring" - so if you intend to put more layers on it, the channels should be spaced closer (and vice versa) in order to maintain the proper spring rate... Steve
Thanks guys - the fine-thread screws worked great on the RC, and I used Keith's recommended screw length for the wall(s). It all went up really easy.
...and yes I caulked :)
It was funny because I had three other guys helping me. They'd all put up sheetrock before, but they gave me really funny looks when I told them that it was two layers, caulked, with green glue in between the layers. They really questioned me about needing to do all that, but once we started putting up the 2nd layer they saw how it all worked.