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Help with drywall on ceiling to replace plaster

Help with drywall on ceiling to replace plaster

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  #1  
Old 01-22-19, 11:14 AM
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Help with drywall on ceiling to replace plaster

Can someone who has installed drywall (as replacement on a 1920’s era house with a plaster ceiling that is falling apart) help me to understand these stipulations on my local code? “For either existing wood or metal studs, the attachment of the Gypsum wallboard to the studs can also be accomplished with screws. The maximum spacing of the screws is 12" on center for both the perimeter and the field of the Gypsum wallboard sheets. Screws shall be long enough to penetrate a minimum of 5/8" into the wood stud framing and penetrate a minimum of 1/4" into the metal stud framing.”

The on center part I think I understand. It means the screws cannot be further than 12 inches apart. I assume the studs will accommodate this?
The second part which reads “for both the perimeter and the field of the Gypsum wallboard sheets” I don’t get. What does on perimeter mean?
If you can draw me a diagram it would be very helpful if its easier to demonstrate or explain that way. I am a complete novice. Never done drywall before. Thanks in advance!

PS Any recommendations on thickness and screw length that are more stringent than code? Here is the full code:
https://www.permitla.org/building/dr...er_detail.html
 
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  #2  
Old 01-22-19, 11:54 AM
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Perimeter means all around the edges of each sheet. You can use 1 1/4" drywall screws. 1 1/4" screws would go in 3/4" when used with 1/2" drywall.

I don't quite get their 12" on perimeter requirement either because on top and bottom, that would require you to put solid blocking between studs that are 16" on center in order to satisfy their requirement. If it worries you call and ask. They are the ones you have to please...
 
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Old 01-22-19, 12:25 PM
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Are you removing the plaster and lath or covering it? I would cover it with 1/4" sheetrock. Screws have to be long enough to penetrate the sheetrock , plaster and lath and go 5/8" into the joists above.
Joists are typically 16"OC. The 12" spacing is in the sheetrock down the joists.covered by the sheet. Sheets should begin and end in the center of a joist so you can butt and fasten the next sheet on the common joist.

If you've not done this before, sketch and measure the coverage so you know how many sheets you need. Consider renting a panel lift. Taping and mudding is a whole 'nother job!
 
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Old 01-23-19, 06:51 AM
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1/4" Should never be used on a ceiling!
Best to use 5/8 or a bare minimum of light weight 1/2" with drywall glue.
It's not going to hold screws and it will sag between the joist.
A lot more work but removing the plaster first would be a far better way.
Were not there to see it but if the plaster keys are failing and the ceiling is sagging in places the new sheetrock will follow the waves and look poopy.
Still going to leave it up, then at least use plaster washers to pull the bad spots back up.
https://www.youtube.com/watch?v=qYSQBH5rbmU
It would also make it far easyer to find the the joist.
If I have to go over plaster I use Bugle head decking screws for a couple of reasons.
There stronger and less likely to snap off when hitting the plaster and the old wood that will be far harder then modern wood.
If the house is really old then I would bet the ceiling joist are already sagging in the middle and most likely the joist are not all the same width.
If this is the case then the whole ceiling needs to have strapping added with shims to get it level and flat before doing anything.
 
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Old 01-23-19, 11:16 AM
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I disagree. I used 1/4" sheetrock over all of the plaster ceilings in my 1920 home over 30 years ago and none of them sag to this day. And they were all screwed on.
I wouldn't recommend removing plaster ceilings to my worst enemy. A contractor with crew and equipment maybe, but definitely not a DIY homeowner.
 
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Old 01-23-19, 12:23 PM
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I assume you used adhesive between the joists ??
 
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Old 01-23-19, 12:30 PM
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If you mean me, I did not, but it's not a bad idea.
 
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Old 01-23-19, 12:43 PM
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I'm surprised it didn't sag between joists since you didn't use adhesive - guess you got lucky.
 
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Old 01-23-19, 12:53 PM
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I'm not sure it was luck. 16"OC is not much span. Sheetrock doesn't stretch, so if you aren't tearing out around the screws and pulling the whole length of the sheet in, I don't know where the sag would come from.
 
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Old 01-23-19, 12:57 PM
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Humidity. It's a well known fact that drywall can sag under its own weight but it's more pronounced when insulation is laying on the top of the drywall.
 
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Old 01-23-19, 01:08 PM
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Where is this sag coming from? Are you saying sheetrock does stretch with humidity? Then it's just as likely to occur with heavier 1/2". Having trouble seeing the logic of this sag claim.
I've offered what i have done that worked for me with a 30+ year old installation. That's all I can say.
 
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Old 01-23-19, 01:47 PM
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Well you haven't gotten up there with a 4' long straightedge to check it either, but I believe you.

1/4" may be light enough that it won't sag much... and yes, the glue is a good idea. The Sheetrock stretches (bows) under its own weight. This especially happens if joist are 24" on center, it's less likely on 16" centers and less likely to bow if there is no insulation laying on it. Lean a piece of sheetrock against a wall in the garage for a few months and it will bend... it's no longer flat. Same thing can happen on a ceiling under its own weight.
 
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Old 01-23-19, 01:48 PM
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Drywall isn't structural, the thinner it is the more apt it is to sag/bow. One of the main uses for 1/4" drywall is for curved walls. You used to have to wet 1/2" drywall to get it to bend but the 1/4" generally follows the radius fairly well, doubled up it matches the adjoining 1/2" walls. As X stated - moisture is hard on drywall and can make it sag.
 
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