Attaching sheetrock to bottom of truss

[kestrel]

Hi,

I have a truss roof. I'm in the process of putting up a new sheetrock ceiling. My trusses are 24" OC. The truss length is 32'. I'm debating whether I should uses furring strips, or dry wall clips, or just attach sheetrock directly to bottom of trusses. Any pros and cons about these methods? Are there other methods?

[Wgoodrich]

Drywall spanning 2' requires 1/2" drywall installed perpendicular to the trusses but only allowed if no water based texture is applied. 5/8" required again perpendicular to trusses if water based texture is applied.

I advise if spanning 24" use 5/8" drywall in any case personal choice to protect from sagging of drywall.

Nails may be used not more than 7" apart or screws 12" apart attached directly to the trusses as minimum standards.

If you want a stronger ceiling then use joist hangers using 2x4 - 24" on center between the trusses. The 2x2 nailers will do little good to add.

Hope this helps

WG

[suemarkp]

In some places with wide temperature and humidity variations, the center of the truss can lift up a half inch or more at times. If you nail to the truss, you could see a big gap in the ceiling along the centerline of the house.

I've never had that problem, but recall that the solution is to put a nailer in the center of the house and not nail to the trusses within a few feet of the centerline. WG's suggestion of using separate 2x4's between the trusses that are joist hangered in place is probably the best solution if this is a common problem in your area.

[kestrel]

I live on Connecticut where temperature changes and humidity have wide variations. I am trying to fix my truss uplift problem. Some of my trusses were uplifting. I took out all the attic insulation so I could see what was going on. That was in early spring 2004. Since then, the trusses have not moved through summer or winter. There was R19 in the attic parallel to the trusses with vapor barrier face done. There was a second layer of insulation running the opposite direction. That was R15. However, this R15 also had a vapor barrier face down on the top cords, thus trapping moisture. So I have taken down all the 1/2" sheetrock ceiling, which in some cases was previously cracked along the joints. It was also popcorned too. So now I have put in R30. I also nailed three sections of 2x4 lateral bracing in the attic--one down the center, and one each to the left and right. I hope that the truss uplift was most likely caused by the second layer of insulation that had the vapor barrier.

What are "joist hangers using 2x4 - 24 on center between the trusses"?? Would you still recommend them?

[Wgoodrich]

YOu insulation is required by the building code. The insulation is required so thick that it buried under the insulation putting the bottom board of that truss under the insulation making it on the warm side of hte insulation. The top part of your truss is exposed to outside temperatures.

Heat and cold cause expansion and contraction. The cold weather temp exposed to the top part of your truss creates a difference between the warm temp of the bottom boards of that same truss causing a sway back horse effect.

Cure is to make a trim on the inside walls secured to the truss so when the truss rises the trim board moves up the wall then when the truss comes back down that same trim board slides back down the wall to original position. You can't stop this and meet the code rules concerning the insulation blanket requirements for heat loss concerns. You just need to install a slide joint of trim allowing the top of that wall to rise and lower with the weather. Otherwise you are going to get the cracks.

This rise and fall will not affect the ceiling drywall being attached to the truss that is moving. The only part that is affected is the connection that is taped and bedded where that truss ceiling moving and wall not moving is attached to each other. This is where you need some give designed such as the sliding trim attached to the ceiling but not the wall to allow the movement.

Good Luck

Wg