Ceiling drywall thickness - how to tell?

I need to find out how thick the ceiling drywalls are so that I can get the screws of the right size. Does anyone know of a good way to do it?

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There are only 3 possible sizes. 3/8, .50, .625.
Buy 1.625"(1 5/8) screws and they will work with whatever you have.
Colbyt

Colbyt wrote:
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Thanks. Is there any downside to using longer screws than necessary?

If you mean longer than 1.625", you shouldn't because you would then increase odds of running a screw into cables, plumbing, etc.
Bill
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Excellent point Bill.

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Normally no. If someone ran a water line improperly there might be a problem. But honestly if .25" makes a difference I have never encountered it.
Colbyt

Colbyt wrote:
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The difference is more like 0.5" (0.375" difference in screw length + 0.125" in drywall thickness). A local big box store carries 1.25" and 1.625" screws for drywalls. The former is for 1/2" drywall and the latter 5/8". I could understand the need for longer screws to hold the weight of thicker/heavier wallboards, but wondered if there's a downside to using the longer screws for the thinner type of drywall. My thinking was, if there's no downside to doing that they could/would stock just the 1.625" kind.

Colbyt wrote:
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The difference is more like 0.5" (0.375" difference in screw length + 0.125" in drywall thickness). A local big box store carries 1.25" and 1.625" screws for drywalls. The former is for 1/2" drywall and the latter 5/8". I could understand the need for longer screws to hold the weight of thicker/heavier wallboards, but wondered if there's a downside to using the longer screws for the thinner type of drywall. My thinking was, if there's no downside to doing that they could/would stock just the 1.625" kind.

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Harder / takes longer to install. Costs more money for extra length you don't need (fewer screws per pound)
Brad

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Drywall screws are used for a lot more things than drywall, that is why they stock them. In my screw collection I stock everything from 1-3". In some special cases I buy longer ones.
For all practical purposes in residential construction the 1 5/8" screw is the correct one to use.
I can't promise you that some dufus did not run a wire or pipe where it should not be. That is the risk you run anytime you work on a structure.
Colbyt

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Remove the cover plate or shroud for a lighting fixture, wall outlet or other electrical device.
You should be able to see the thickness of the dry wall along the side of the electrical box.
First, turn off the electricity at the fuse box/circuit breaker for safety.
TKM

TKM wrote:
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That's a good tip. Thanks.

All Thumbs wrote:
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I'm puzzled by your question, but maybe I'm not reading it correctly.
I presume that if you're asking that question it's because the "ceiling drywalls" are already in place so you can't measure their thickness directly.
If that's the case, why do you need screws? Is it sagging down in some places and you want to try and correct that with some more screws?
Just wondering,
Jeff

Jeff Wisnia wrote:
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I made the mistake of stepping onto the "floor" while in the attic and as a result got a few popped-out nails.

All Thumbs wrote:
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Well, If you stepped on it in the attic, then you should be able to see if there are any wires or pipes running through whatever joists or strapping you need to screw into, and keep away from them if there are.
So just grab a few screws about 1-1/2" long and start screwing.
Glad you didn't fall right through. :-)
Jeff