Hanging ceiling joists from a beam in attic 1

[mfstructural]

Hey everyone, I have a question regarding removing a bearing wall in a residence. There is a 6' long wall that the client wants to remove. There are 2x8 ceiling joists lapped and bearing on this wall. In addition, there is an opening adjacent to this wall where to facilitate walking between the kitchen and living room. There is a 2x8 beam bearing on the end of this wall. I know we can shore up the ceiling joists, and construct a header below the ceiling joists and opening. The issue with this is that the client wants to have a flush ceiling. So what I'm thinking of doing is shoring up the ceiling joists and adding posts that extend up past the top of the ceiling joists. Then, a beam will span between the two columns and the ceiling joists will be hung from the beam with a steel strap and/or orthogonal metal ties. Does anyone have any input or additional things I should consider?

It's a shallow roof with vertical 2x4s every 3 to 5 feet. I think because the vertical 2x4s are in place, vertical load from the ridge will be forced into going into the bearing wall below. I attached some pictures. Any input on that? The shallower the roof the more prone it is to spreading. So I think some tension is going into the ceiling joists/ties, but because of the vertical 2x4s and the shallowness of the roof, some loading from the roof rafters will go into the 2x4s. I will obviously have to design the header for the roof loading.

Thanks,

 

[SlideRuleEra]

I had a client who want to do exactly the same thing (remove load bearing wall, flat ceiling). Made sure the overlapped ceiling joists were secured to each other, then had him add vertical members to turn the joists / rafters into king post trusses, see sketch. The horizontal, flat 2 x 8s create secondary load paths tying together all modified trusses and existing ceiling joists that are still supported by the load bearing wall.

His insurance agent required an engineering design and approved the plans and as-built modification. This was 16 years ago, still no cracks or other signs of distress in the sheet rock ceiling.

http://www.SlideRuleEra.net

 

[mfstructural]

Thanks slideRuleEra, this is pretty much what I'm looking to do. How long of a span was the modified truss? I'm looking at 30' total. You had only one king post installed? Do you think it's overkill to have two, one on each side of the ridge to support the ceiling joists? I know if you ensure they're connected it might be overkill, but for good measure you could add one to each side.

 

[mfstructural]

Also, this is a little off topic but not too much. I recently looked at a house being renovated that had 2x4 roof rafters spanning about 15'. The roof was pitched at about 8:12, with 2x4 ceiling joists/ties. There were some baseboards inserted vertically at some point, presumably because the rafters were sagging. I'm going to recommend adding vertical supports like slideruleera has shown above between the midspan of the rafter and the ceiling joist. The only thing that concerns me is the vertical load that will be then induced into the 2x4 ceiling joist. Instead I was thinking of attaching the reinforcing 2x4s or 2x6s together at the midspan of the ceiling joist and then angle those up to connect to the midspan of the roof rafter. that will force it behave more like a truss. Any thoughts on that? I included a photo

 

[jayrod12]

I would say constructability... There's usually a ridge beam or ridge board(I've seen a 1x6 in a lot of cases for a ridge board just there to keep the rafters in place until the sheathing is on) and therefore you can't go up directly in the centre and fasten appropriately to each rafter. It's quite likely that the added dead load that close to the "panel point" won't overload the rafter, but you'd need to run the number.

 

[SlideRuleEra]

mfstructural - Agree with jayrod, a little eccentricity on location of the king post is not a big deal:

1) King post tributary area of ceiling loads is relatively small compared to other loads.

2) Adding the king post gives a load path for ceiling loads to replace the removed load-bearing wall.

3) The existing "members" (rafters & ceiling joists) are conservatively sized, compared to a "real" truss.

4) Adding the king post adds nothing to bending stress in either the rafters or the ceiling joists. It does increase compression of rafters, tension of ceiling joists, and adds load to walls supporting the "truss"... which means, run the numbers, per jayrod's comment. Span of 30' is just a meaningless number until calcs tell you what that means. The span for my project was 24'... just another number unless there are calcs. Check the rafters and ceiling joists for combined bending and axial loading. Also, the king post for tension, or course.

Concerning your other question, I would not add members that introduces additional bending to existing members that appear marginal... add axial load, maybe. Don't guess, check it.

http://www.SlideRuleEra.net