Need help with ceiling joist problem

[minicus]

To preface, any and all help/feedback is appreciated. We built a new home in 2005 with a builder who went bankrupt 3 months after completing the home (this is one of many problems). My current problem that I just noticed is it seems the builder skipped ceiling joists in our bonus room for some reason, so instead of being 16” on center they are 32” on center. For reference, the room is 40’ long, 20’ wide, has a 12/10, and there are 6’ knee walls on both sides of the room, and all rafters are 16” on center. The current joists are 2x8 and span 12’ for the most part. My questions are is this structurally sound? If not do I need to add the rafters he skipped? Does the fact that there are knee walls mean that it is ok to skip rafters? And lastly what would you do to fix this problem?

[Richard A Hetzel]

The ceiling joists are probably adequate. The problem, if there is one at all, would be the ability of the gypsum board to span the 32 inch centers. If he used 1/2-inch gyp. board, it will probably sag noticeably between the ceiling joists. If he used 5/8-inch gyp. board, it will probably sag considerably less. When you look at your ceiling, is it flat, or does it appear wavy? If it's relatively flat, you can sleep well at night. If there is a noticeable dip between the joists, then you'll have to decide whether to live with it, or try to correct it. The seat of my pants tells me that once it has sagged, simply adding new joists might not bring it back to flat, but I'll hope someone with hands-on wallboard experience might offer an opinion about that. Other than the possibilty of a wavy ceiling, there is no structural inadequacy, in my opinion.

[Don_P]

Edit, I stopped for breakfast, I see Richard has posted. He may well be correct, but I'll leave this up for just another thought.

You are mixing terms I think. Rafters are the angled members. Ceiling joist are the horizontal members tieing the rafter feet together to prevent them from spreading and providing support for the ceiling to nail to. Structurally there are enough ceiling joists to keep the rafters from spreading... but they need to be well connected to the rafers over the walls below. It looks like that might be sketchy from the photo, check to see that they make it to the walls with at least 1-1/2 inches bearing over the wall plates and that there is adequate nailing between the rafters and the cj's.

There are not enough ceiling joists to properly support the drywall it will sag over time.

Its going to be about impossible to fit in more full length cj's. You can block between existing cj's on 2' centers and screw to the blocking from below. If the connections between existing cj's and rafters are inadequate then that won't help anything. 8' ceiling joists from each side on opposing faces of the rafters lapping across the center would work there. In the 1-1/2" gap a vertical 2x4 post up to alongside the ridge to support the lap then blocking to fill the lap area each way. Fill this with nails. The cj ends at the rafters would get a 40 degree cut and are stuck out to the roof sheathing to givwe plenty of nailing room there. Without knowing snow and roof loads this is real generic advice. You should probably get an engineer in there to take a look. There may be a better solution... blocking and metal straps, etc.

It looks like a little insulation is in order when this is taken care of.

He could have framed the whole thing on 24" centers, would have used no more wood, and everything would have been ok.

It also looks like you need 2x4 blocking at the end wall where I'm seeing insulation to seal those chimneys off.

[Roy J.]

The builder left out the collar ties and purlins too?