Hmmm, far off from this portion of the project...
But a thought just crossed my mind...
If one were adding, say, 3 layers of 5/8" sheetrock to the inner-leaf ceiling -- indepenently framed, but NOT counting for the strength of the joists -- doesn't this really get a little iffy with relying on the pull-out/pull-through strength of the screws/drywall?
In other words, might the potential weight on the lowest layer of sheetrock cause it to simply pull-through over the screws (maybe not right away, but over time)?
What are the thoughts on this?
thanx,
K
Multi-layered inner-leaf ceilings....?
Originally posted at johnlsayers.com, topic 6709.
I have thought about this, too, but I don't think it's a problem.
A single layer of drywall will have dozens of screws holding it up, provided it is installed in compliance with code. There are specific requirements for this (the "screw schedule"). When a panel is hung, each screw is holding up about a pound or two.
When you hang the second layer, you're doing the same thing, using the same screw schedule. (Note that there have been suggestions here to use a "half schedule" pattern for the first layer(s), but that is not to code, and I don't recommend that for safety reasons.) So, again, each screw is holding up a pound or two.
If the initial layer(s) is/are installed correctly in this fashion, there is no downward pressure on the subsequent layer(s), so there is no additional stress on the next series of screws.
It is critical, however, to use progressively longer screws so that you have the correct amount (one inch I believe) of penetration into the joists. You certainly should not use 1 5/8" screws on your second layer, as you would achieve only 3/8" of penetration. In that case, risk of pull-out would be very high, and you couldn't pay me enough to stand under that ceiling! :shock:
--Keith :mrgreen:
EXACTLY what I was worrying about.... Yeah the longer screws might allow as much as possible for each layer to be 'separately' supported, and not stacking the loads on the lowest layer's sheetrock and screws.... K... It is critical, however, to use progressively longer screws so that you have the correct amount (one inch I believe) of penetration into the joists. You certainly should not use 1 5/8" screws on your second layer, as you would achieve only 3/8" of penetration. In that case, risk of pull-out would be very high, and you couldn't pay me enough to stand under that ceiling! :shock: --Keith :mrgreen:
You got it. 8) When you consider that it's actually the heads of the dozens of screws that are holding each panel up, and the threads of the dozens of screws that are holding the screws up, it's a little less scary, huh? :) --Keith :mrgreen:EXACTLY what I was worrying about.... Yeah the longer screws might allow as much as possible for each layer to be 'separately' supported, and not stacking the loads on the lowest layer's sheetrock and screws....