Attaching Drywall, to ceiling need ideas/recommendations

gregt848 · 10-24-2009, 06:57 AM

Need some help here to see what is allowable and what would successfully work as I am starting this tonight and tomorrow. You may have to picture this, Basically, to not get into everything to indepth, I am removing my collar ties and installing plywood gussets around the ridge board. I had a structural engineer come out, he recommended the gussets, have a stamped letter and the building department gave me the go ahead. They also said it would be ok to run a 2X4 at the bottom of the gussets sandwiched between them running rafter to rafter. This 2X4 would serve as a nailer for blueboard, lightning, etc. as well as allowing for a flat ceiling span before sloping down the rafters. I am only making the gussets about 4'. Since I have a shed dormer off one side of the ridge the the span is greater than if it was two steeply sloped sides, this makes the 2X4 extend (2') past the end of the gussets (4') and them tapers down to meet the opposing rafters. I am trying to figure out if that part will be ok or will I get a hard time about it. Where the 2X4 gets really thin, the drywall screw will also bite into the rafter above so it should hold. I just want to address any potential problems before the happen. Any other ideas on how to make this work? I was told that I could make the gussets 6' which would be total span, but that would be a lot more plywood because with the 4' I am able to use the short side. Thoughts?.....More than appreiciated

gregt848 · 10-24-2009, 06:01 PM

Anyone got any ideas/advice? I was thinking maybe those metal nailing plates on each of the 2X4 ast the gussets. I am trying to post a picture but can't find the battery charger

**Gary in WA** · 10-24-2009, 08:59 PM

"this makes the 2X4 extend (2') past the end of the gussets (4') and them tapers down to meet the opposing rafters. I am trying to figure out if that part will be ok or will I get a hard time about it." --- You can't just nail the 2x4 on the other side of the plywood from the rafter? Isn't the plywood acting as a ridge tie to hold the rafters together at the peak? The collar tie was installed to reduce the span of the rafters from bearing to bearing, making them stronger. Sounds like you are going the correct course, here is some reading for you on collar ties, purlins and struts. Page 257: http://books.google.com/books?id=1fI...20ties&f=false
With tapering to a point, they may call you on this as it may not transfer the loads down correctly. Here's the same idea, on beams and joists, page 38-40: http://books.google.com/books?id=iwS...joists&f=false
An alternate way to attach shed dormer rafter ties/ceiling joists, page 43-47, Fig. 31-B: same book.
Be safe, Gary

gregt848 · 10-25-2009, 08:08 AM

I get what your saying put the 2X4 on the outside of the gusset? I think that would work, but the section that extends past the gusset I would need to add a plywood spacer to bring it to the same level. What do u think?

**Gary in WA** · 10-25-2009, 12:55 PM

Yes, just use a string line pulled tight to get the ceiling framing all the same level, otherwise it will show with drywall. Set the stingline 1/2" below your finished level so one member doesn't touch line to set all the rest lower.
Be safe, Gary