My garage has 24″ oc trusses and the ceiling drywall has bowed or “bellied” down a little inbetween each joist/truss. Now, I have 2 additions scheduled (a kitchen addition and a garage with finished space above) each with 24″ spaced trusses. What can I do to avoid drywall bellying down?
Jim
Engineered-stone shower panels are waterproof, but proper installation relies on tight seams and silicone sealing.
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Replies
Strap the ceiling at every foot with 1 by 3's. Some try to skimp with 1 by 2's but spend the extra dime and do it right.
Gabe
Run 1x3 straps 16" OC perpendicular to the trusses and fasten SR to them instead?
Just use 5/8" drywall next time. I've never had trouble with it bowing down.
Veni, vidi, velcro: I came, I saw, I stuck around.
All the above methods work. Another one is to use special drywall.
Ask your local drywall supplier. (non sag-or sag resistant?) something like that.
YCF Dino
Edited 10/7/2004 10:13 pm ET by YCFriend
We strap up rollformed steel "RC" resilient channel on 16" centers, then hang 1/2", or hang 5/8" straight to the 24-center truss chords.
I say "we" but really am speaking for my rocker.
Go to Dietrich Industries site for a look at RC. Your local supplier probably stocks it. It used to be cheaper than 1x3 furring, but hey, with prices as crazy as they are now, particularly steel, who knows?
Don't all trusses bow. That is what the clip are four to attach the furring. I always thought a L/120 roof could bow several inches in the middle????
Use screws or ringshank nails to fasten 1x3 furring directly to the truss chord bottoms. Use screws for fastening the RC channel. Then screw the rock directly to the furring or channel.
Truss clips are used to fasten the tops of wall plates to trusses. They allow upward truss chord movement, while wall movement normal to the truss chord is still braced.
Don't know what you mean by "an L/120 roof" as it might apply to a trussed roof design. L over something refers to beam deflection under load.
"Don't know what you mean by "an L/120 roof" as it might apply to a trussed roof design. L over something refers to beam deflection under load."
The L over something also applies to roof trusses. Around here the limit is L/240 for live load, and L/180 for total load.
Personally, I think that's WAY too much. If you have a 40' truss at L/180, that means you can have over 2 1/2" of deflection.
Fortunately, it's not typically a problem. Most trusses we build are pretty high pitched, and don't have much deflection.Happiness is having a scratch for every itch. [Ogden Nash]
"I always thought a L/120 roof could bow several inches in the middle????"
I don't think you're going to get several inches of deflection in any residential roof trusses that I've seen.
Most SEANONAL movement you'll get will only be 1/2" or so.Sex is not the answer. Sex is the question. The answer is yes.
I live in Buffalo NY arae and when 7ft of snow flys.....there are many roof collapes. I am sure trusses sag at least 1/5" with 7' of snow on them. A 50lbs truss maxes out about 3'6" someone once told me.
Thanks
"A 50lbs truss maxes out about 3'6" someone once told me."
Don't know why they'd say that. A roof truss designed to be set 2' O.C. is maxed out at 2' O.C. at whatever load its designed for.
Obviously there are safety factors. But it's not as simple as what your friend told you.
It's a shame you have roof collapses up there. With the technology available these days, there's no need for that. Houses can be built to withstand whatever snow loads they need to.There is no doubt in my mind that millions of lives could have been saved if the [German] people were not "brainwashed" about gun ownership and had been well armed. [Theodore Haas, Dachau Survivor]
No 3'6" of snow maxes out a 24' oc 50lb. roof truss. And then they collap. Everything are around here is about the wet snow from lake effect snow bands.
O.K. - Sorry I misunderstood about the 3' 6" thing.
The weight of snow varies with how wet it is. Wet snow would obviously be heavier than dry snow. I assume lake effect snow is wet, although I've never been around it.
Trusses are designed with a 3X safety factor. So a truss designed to carry 50 PSF should theoretically carry 150. But in reality, there are flaws in the lumber, misplaced plates, etc. So the safety factor goes down to somewhere around 2X the design load.
A lot depends on WHERE on the truss the snow is. Snow almost never piles up evenly across an entire roof. It's often wind driven and piles up more on one side than the other. Or it drifts up against a second floor wall, etc.
But like I said - This can all be dealt with easily if it's planned for when the house is built. So it kinda bugs me when I hear of roof collapses from overloads. It's a lot easier to do when it's built than to clean up the mess afterwards.Is It Cold In Here, or Is It Just You?
BOWED???,NEVER, unless of course, they were only engineered for 5' of snow and you got 15' or more on them.
Coz,
Do not know exactly what your builder did, but my house is constructed with the roof trusses on 24" centers and I do not have any problem with the sheetrock sagging or bowing, including the garage. I am not sure if it is 1/2" or 5/8" . The house is 25 years old and I have been in it since new.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
If you can , nail a strongback across the 2x4 members in the attic space. This is 2 2x6 nailed together in the shape of a t,invert this and nail to top of 2x4. This acts as a beam.
Around here they either use 5/8ths regular or 1/2 ceiling rated rock, it even says it on the drwall "ceiling board". Have never seen 1/2 ceiling drywall at the big box stores, maybe that was the problem, someone used plain 1/2 on the ceiling
maybe the garage is not insulated and your having mositure problems making the drywall sag, just a wild guess
my rocker uses the 1/2 ceiling board and I have seen no problems