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The ceiling in one of my bedrooms is framed with 2X6 joists, 16″ O.C. Framing is dry/7 years old. Top side of joists has 5/8″ plywood glued & screwed. Length of joists is 10′. I see a small amount of deflection in the joists when walked on from above (attic). Will drywall seams crack readily if applied to this ceiling? Will solid bridging along seams help this situation?
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Nick: What's on the ceiling now, and how well does it work? 5/8's flooring on 2x6's seems borderline. Not surprising that is flexs. Blocking would help stiffen it up. You could always screw and glue 3/8 OSB to the underside. That would stiffen it up A LOT (stagger joints relative the drywall) and cover with drywall. The floor above would also be noticably less bouncy to one's feet. It would only be $40 of OSB. -David
*2x6 is very marginal.When framing as a youngster back east, we installed 1x2 firing strips accross the underside of all ceilings (a regional thing), which it was claimed, would stop deflection of the dry wall. I think for 1/2" drywall, which is very marginal as well, I would definitely recomend that and/or some good blocking accross the joist.
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David: I started a whole house renovation (including 2 small additions) torn down to the studs, replacing all electrical, so I have been slow in getting to the "finish" work. There is nothing on this ceiling now. At the time the joists went in, I sized them to those in the rest of the house, not thinking ahead. The original sections of the house had better, thicker lumber and a plaster finish which I tore down because it was also badly cracked. At the time I attributed the cracking to settling of the house with the years, but the longer I worked on this project the more concern I learned for the use of drywall as a ceiling material.
Because of the fear of cracking, my most recent intention was to put up a wood ceiling-T & G cedar or fir, and eliminate the worry all together. Alas, money is also a question so I have been re-thinking this and re-considering the use of drywall. However, if money were not an issue, would you abandon the use of drywall and use wood? Thanks for your suggestions.
*Scooter: Do you think it be advantageous to up the thickness of the drywall, perhaps to 5/8? That thought occurred to me, but the seams would still be vulnerable to cracking wouldn't they? Or are you thinking that that with 1/2" there could be some cracking within the field as well?I'll ask the same question of you that I put to David Thomas-if you could afford to use wood as a ceiling material in this application, would you abandon the use of drywall? Thanks much
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Hi Nick,
Don't do anything to add weight to the ceiling.
Drop the 5/8 drywall idea, doesn't add enough strength to compensate for the added weight.
Drop the 1/2 idea idea, doesn't do anything for the strength.
If you can double up on the 2x6s it will certainly help to spread the load.
If you can add solid blocking and you can make it continuous, this helps. (make sure you remove as much load as you can upstairs before you do this)
Use a finished pine board, t & g vee joint and shoot it to the ceiling. Minimize your weight and maximize your strenght.
Gabe
*Nick: I'm in the same dilemna, money-wise. T+G strip birch would great as the ceiling but is way more $ than 5/8 drywall. But with 2x12's, I'm going to mount the drywall now, get moved in sooner and later install the birch over it. For your case, yeah, I'd go wood if the money is there. More strength/weight as Gabe points out. Not as much strength/weight nor strength/cost as plywood, but how do you make plywood look okay? Only if you cover it with some (1/4") sheetrock. -David
*Adding layers seems a bit experimental to me. It may reduce flex, but it will put more strain on the 2x6's that are already in place.Without consulting a span table, my off the cuff recommendation would be to add more joists. Try doubling up every other one at first, if that is insuffucient you may need to go beyond that. Ten foot 2x6's aren't horribly expensive, and, in my opinion, would be your best bet at a stronger and less flexible floor structure.
*Nick:To answer your question, 1/2" drywall is ok out here in SoCal, but most tradesmen prefer 5/8", because it flexes less (less showing of bumps) and is a better fire retardent. I don't have a strong preference, assuming the bottom of your joists are nice and straight.If not, use 5/8". If they are real bad, I'd consider using firing strips to make them so, then add the 1/2". Borrow an 8' level to check them.Neither 1/2" nor 5/8" will resist massive movement (Hey we had a 3.5 quake out here today), so if you are experiencing deflection, and intend to walk around on those attic joists, I would: (1) Put some real stiff plywood on the top of the joists, like 3/4"; (2) Add blocking between the joists; and/or (3) double up on every 2-3 joists with a second joist sistered to the first. Any one or any combination of the above will stiffen the joists considerably.Wood ceilings are nice, but fairly expensive, and add no fire retardent. They are also a real pain to add ceiling fixtures to. You won't get a lot of strengthening from 3/4" pine on the bottom.T&G ceilings were generally used for informal parts of the home such as porches and the like, but if that is the look you like, go for it. You might also consider adding some 1/2" ply and putting in some tin ceilings. Both will be triple the cost. But hey, its your home.
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> The ceiling in one of my bedrooms is framed
> with 2X6 joists, 16" O.C. Framing is dry/7
> years old. Top side of joists has 5/8" plywood
> glued & screwed. Length of joists is 10'. I see
> a small amount of deflection in the joists when
> walked on from above (attic). Will drywall
If the above room is an attic, why don't you attach a "strong-back"? That's a piece of 2x4 running perpindicular to the beams and lying flat, attached with nails or screws. Then another 2x6 or larger, attached to the 2x4. Somewhat like this:
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The strong-back will distribute the load among the existing beams and help prevent deflection.
OTOH, I've found t&g cedar to be much more expensive than drywall. Lowes in central NJ has unlimited 1/2 drywall for under $6.00 a sheet.
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Nick,
Ditto Frank....and Gabe.
Add a stiff back or "strong back" to the top of the joist if this is attic space. 10' is not that much of a span even for 2x6, if there is no live load above. Just storage? Don't worry about it. I like the idea of tight bridge blocking. That along with the stiff back should solve your problem.
You should be fine.
A wood ceiling would look nice, but no strenght there. Just no stress cracks in the drywall.
As Gabe says, forget the 5/8 vs 1/2. Neglegible as far as I'm concerned.
The strenght is in the joist system, bridge blocking and stiff back.
Ed. Williams
*My ears were burning!Ahh Dennis, one of my favorite quotes!Nick, you have been given a plethora of advice, most of it bad. The only thing that i would do, is add more framing lumber. Gabe suggested doubling each joist, and I agree. The problem, is that most 2x6 is spf, a very poor structural species. See if you can find some doug fir, or rip some doug fir 2x12' in half, and double every joist. Skip the solid blocking, and strapping. It is a waste of time and money. If you want to throw more money at it, add a third joist between the doubled members.Even then, you will still have some deflection. It is alwasy there in wood frame construction. Drywall will be ok, if the deflection is not too severe. Too severe is a debatable issue. It does sound like you are over worrying.One other sugestion would be to install a "false" ceiling independant of the floor above. This couldbe done by installing a new set of 2x6, without nailing them to the existing. Then add a furring strip along each joist, The drywall will then have a 3/4" airspace that will allow the floor joist to flex into. blue
*Frank:$6 a sheet for 1/2" - is that 4' x 12'? Wow!
*I deleted two posts that upon re-reading were a waste of readers' time. They contained no useful information, they contained no insults implied or otherwise - aw heck, I am just wordy tonight. Good night all.Dennis
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I appreciate all the responses to my question. I see the logic in starting where the problem begins...by working on the joists first. I will sister the joists that are in the main walking area of the attic above this room. Though there was variable enthusiasm for solid bridging, I'm going to try some anyhow...particularly out to the eaves where I might not want to add joists, but where there should be less concern since no one can walk there. I don't think I want to use a strong-back since the area of greatest concern is also in a walkway where someone could trip and fall. The lumberyards here don't carry a lot of Douglas Fir, but I called and they do have 2X10, which I can easily rip to 2X6 as suggested. I'm glad there wasn't strong support for using 5/8 drywall vs. 1/2 on the ceiling. I don't mind admitting that I don't look forward to hoisting the extra weight. It's true that the wood probably doesn't really belong in the bedroom anyhow, but I hadn't thought about the issue of retarding the spread of fire and will be glad to save the expense as well.
Thanks again for the help.
Nick
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The ceiling in one of my bedrooms is framed with 2X6 joists, 16" O.C. Framing is dry/7 years old. Top side of joists has 5/8" plywood glued & screwed. Length of joists is 10'. I see a small amount of deflection in the joists when walked on from above (attic). Will drywall seams crack readily if applied to this ceiling? Will solid bridging along seams help this situation?