residential wood truss interior bearing walls
residential wood truss interior bearing walls
(OP)
Looking for general thoughts on what spans/conditions at which one should start considering interior bearing walls to support wood roof trusses in typical residential applications.






RE: residential wood truss interior bearing walls
As an example, you could have a long truss which was designed for the full span and in which case all the interior walls do nothing structurally. On the other hand, you could have a much shorter "truss" that resembles a truss but is actually 2 half trusses that each bear on an interior wall. My point is that the span does not dictate if the interior walls are bearing or not.
General rules:
If a wall is bearing it must lie directly under a joint on the truss above in order to provide support to the truss.
If a wall is bearing there must be a mechanism to bring the load it picks up to the ground. If it is a single story house, the wall must be on a footing, not simply on the floor. If it is a 2 story house the wall must rest on a strong and stiff enough beam that is capable of bringing the load to the foundation.
I would never make judgements about removing interior walls in my house based on things I read on the internet. Hire a structural engineer to come for an inspection. It will not take a knowledgeable engineer very long to determine if the wall in question is load bearing.
Great spirits have always encountered violent opposition from mediocre minds - Albert Einstein
RE: residential wood truss interior bearing walls
No interior bearing wall:
Pro:
-Provides flexibility for renovations in future
Con:
-If long span, truss may get more expensive
Interior Bearing wall
Pro:
-Distributes load more through several load paths
Con:
-Additional foundations required
RE: residential wood truss interior bearing walls
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: residential wood truss interior bearing walls
RE: residential wood truss interior bearing walls
RE: residential wood truss interior bearing walls
RE: residential wood truss interior bearing walls
RE: residential wood truss interior bearing walls
RE: residential wood truss interior bearing walls
How do you finish that joint? I don't imagine that it makes a nice, clean line.
RE: residential wood truss interior bearing walls
You have to provide a slip joint btwn. the top of the wall and the trusses, so as to provide lateral support for the top of the wall, but still allow these vert. truss movements. We used to do this with a blocking means on the top plate of the wall, at each truss, but always got a fight from the builder and carpenters for this extra work. Simpson and USP now provide a piece of "L" shaped hardware which does this, with slots in the vert. leg, loose nailed to the truss bot. chord, and solid nailed to the wall top plate. I've actually seen walls hard nailed at the trusses, lifted right off the floor below when the trusses lifted up, there was a 1/4"+ gap btwn. the bot. pl. and the sub-fl.
Regarding the ceiling sht.rk....: in its crudest form, nail a 1x6 x 20" long flat to the top of the wall, btwn. each set of trusses, and nail/screw the clg. sht.rk. to this, or at least push the wall sht.rk. up under the clg. sht.rk. and up to this blocking. But, then do not nail the sht.rk. to the trusses until you get 16-18" away from the walls. This allows the sht.rk. to flex without popping nails and with less likelihood of cracking significantly at the walls. A small cove molding or some such nailed to the wall, but not the clg. will hide this joint. You can't nail to the clg. because the trusses move and this joint does not. In some cases a larger cove molding can be nailed only to the clg. (to move with the clg.) and be allowed to slide vertically at the wall or on another flat piece of molding affixed to the wall. This joint may show the movement in paint or stain discoloration from behind the lower toe of the cove. The above works pretty well along the length of the wall which is perpendicular to the trusses. The most difficult detail area is at the end of the wall which goes up to the clg. where you have to let the clg. sht.rk. flex on both sides and for about 16-18" beyond the end of the wall. And, you want to avoid sht.rk joints in this immediate area too, if you can.
RE: residential wood truss interior bearing walls
RE: residential wood truss interior bearing walls
My office condo has end bearing roof trusses and ceiling/wall cracks. Some owners spend a good deal of money trying to fix them. They are not large, I accepted them long ago. But I love the ability to rearrange my interior walls as I want without much thought to the roof/attic or my downstairs neighbor.
I suggest you have a discussion with the Architect. If the building is to be inhabited by people who will hate even a small crack in the ceiling/wall, then break the trusses to reduce arching.
DBennett
Lone Star Engineering, PC
www.lonestarengineeringpc.com
RE: residential wood truss interior bearing walls
Also bearing conditions at the truss and tie downs. Longer trusses need more bearing on a wood top plate and have higher uplift. Pay attention to girder trusses especially. DON'T assume the truss designer is looking out for you on this. The fine print on the shop drawings will tell you the things they are not responsible for and they don't usually flag it for you if you don't meet bearing requirements.
Deflections as the conversation is going should also be a concern. L/240, L/360 etc... then you should consider a max limit. Keep in mind -stiffness attracts load. SO if you have partition walls under a long truss the floor joists under will start to deflect too. I once reviewed a home under construction where the floor was deflecting like crazy +2" without any occupation yet. Turns out, the roof was using a "partition wall" as a nice support structure and the floor was willing to help out.
MAP
RE: residential wood truss interior bearing walls
After 40' - your call.
Get with your local truss designer and work out the details.
My choice - clear span if at all possible.