Drywall sag

Page 1 of 2  

If I have ceiling joists that are 48" apart, will 5/8" drywall sag if mounted on it?
I'm not seeing too much information about that around, even though I'm pretty sure 48" is pretty standard framing for a basement.
I made the mistake of putting 1/2" up the first time - bad bad mistake that cost me dearly. But 5/8" isn't that much more. The idea of installing 2x4's between the studs isn't my idea of a fun time, especially since it will introduce more margins for error unless I'm a demon for measurements.
I am also considering the idea of using plywood backing over the joists as a way to give the drywall a larger surface to attach to - even if it isn't structural it will still remove any sagging. But that option has the detraction of reducing my headroom by 1/4" or more. I know it doesn't sound like a lot, but it all adds up - not to mention it will make adding lighting fixtures a huge pain in the ass since you can't cut plywood with a drywall saw.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eigenvector wrote:

USG recommends 5/8" gyp bd be supported by joists 16" O.C. if the gyp bd sheets are parallel to the joists and by joists 24" O.C. if the sheets are perpendicular to the joists.
TB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eigenvector wrote:

Ceiling joists at 48" are way too far apart, even for 5/8" ....if you want the ceiling to look flat
IMO even 5/8 is a stretch at 24" .....I would use 1/2 with joists at 16
cheers Bob
PS the drywall / plywood combo will cut very easily with a jig saw
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
BobK207 wrote:

I'd be curious to know where any building code allows 48" as routine ceiling joist spacing, whether in a basement or anywhere else. I'm betting you don't have a building permit.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Not required, I'm repairing existing work - I asked first. But thanks for playing.
As for 48" separation, I've seen a lot of houses with this kind of joist separation. Perhaps its peculiar to my house construction, pier and post foundation, but certainly not unique.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eigenvector wrote:

It is not pier and post, it is post and beam. Yes it is common in some parts of the country and it is for the bottom floor. The posts are usually on 8 foot center and the beams are 4 feet apart. Beams are often double 2x8's or double 2x10's. It is used for crawl spaces because who would want to live in that kind of room? Sounds like a basement that was put in after the house was constructed with a crawl space.
Or, are you talking about old type of post and beam construction with very large beams and longer distances between posts?
In any case, the minimum you need are 2x4's between beams with the 2x4's spaced on 16 inch centers. Or use a drop ceiling, not drywall.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes, it will look like crap

No, it is not

One method looks like crap and you have verified that. The other method is correct. Your choice, do it right or a second half assed job. You can get away with 2 x 3.

That certainly narrow down the options. 1/4 plywood is not going to help much anyway. That too may sag at 48" spans. That gravity thing is not going away.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I see this in a lot of houses where I live, especially in downstairs garages.
The roof joists are all 24".

That sucks. That adds a hell of a lot more work that has to be done.
Attaching the studs to the existing joists itself is going to be a trick
Nothing for it then but to do it right.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
How about screwing 3 46" 2x3s or lighter steel studs to the drywall before screwing the drywall edges to the joists on 4' centers?
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eigenvector wrote:

I'm thinking that some mis-communication is going on here........support members for drywall or even plywood would be difficult to get to perform at 48" oc
that's just too far for the sheet material to span unless, in the case of plywood, it was really thick
maybe we need a better description of the exisitng condition & the project objective
You mention what seems to be a post & pier foundation system?
what size are these "ceiling joists" that are at 48" oc? are these really "support beams" for the floor joists above?
I may have given poor advice based my lack of understanding of the situation
cheers Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'd buy a cheap Harbor Freight nail gun and a $99 miter saw. It won't be all that bad, especially if the dimension between existing studs are consistent. It would be easier yet to put them on top of the joist, but you lose a lot of headroom that way.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eigenvector wrote:

No were I have ever seen.
Without seeing exactly what you are working with I can only suggest you need to get that down to 24" or better yet 16". I would go for 16"
--
Joseph Meehan

Dia \'s Muire duit
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Now you know why furring stock is used as strapping. Lay it out to make full use of the tapered drywall edges on 16" centers.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
yes,
s

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eigenvector wrote:

Time to buy a chopsaw.
Cut each joist 1/8 - 1/4" long and test fit. Pare the ends until it fits.

Cheap circular saw or jigsaw with 2 x 4 guide fence.
Two more options: Hang 2 x 4s across the joists, 24" apart. Possible downside is this will lower your ceiling 2". That, or a cathedral ceiling.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A 1x4 may work as well. I was actually thinking of cutting 48" 2x4 spans and mounting them between the joists at 16" spacings. It's a heck of a lot of cutting and physically mounting the 2x4s to the joists will be an issue (not insurmountable though). I'm not in a hurry so I can take my time.
Anyways, I got what I needed from you all, thanks again for the options and the responses.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Don't even consider 1x4's for this. 2x4's on 16" centers is the method that will be most successful. You could install them with metal brackets if you don't like accurate cutting and nailing but if you get set up properly it should not be a difficult job to just cut and nail.
Don't forget to check the evenness of the existing joists. If they are not reasonably straight and even (level is not very important) you would want to use a guide string and shims as needed.
Don Young
Don Young
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eigenvector wrote:

Maybe you're trying to solve the wrong problem.
Forget the drywall - it's too heavy.
Perhaps ceiling tiles - they're 48" and should be quite easy to install flush with your joists.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Eigenvector wrote:

Let me suggest resilent channel (metal) at 16" centre perpendicular to the joists. Then you can use 1/2 " drywall attached using drywall screws. And the channel will reduce noise/vibration transmission between the two areas ... if that's a consideration.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
bowgus wrote:

The channels are designed to span 24" max, not 48" - so they'll sag too.
I thought of a suspended drywall ceiling, but the main runners couldn't handle 48" spans either.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.