The interior wall on the top floor is labeled as “non-load bearing”, and the wall directly below it is “load bearing”. Why is the wall on the top floor non-load bearing?
If the wall on the lower level is supporting the weight of floor above, isn’t the top floor supporting the weight joists above it?
Look again, the arrows are pointing to “interior” walls, they are not carrying any load other than their own. The exterior walls of the top level are load bearing.
Simon,
The wall on the lower lever supports the weight of the level above it, and the upper floor does not support the weight of the trusses?
When properly designed, typically, the truss load bearing/transfer points are at its edges or the exterior walls. The floor, on the other hand, will transfer some of its load in the middle because the joists alone are not strong enough and need help from midspan.
Saman: The roofing structure in the photo shows trusses. The bottom cord of the truss does not require support, therefore that partition in the centre is not load bearing, as Simon said, while I was typing.
Hope this helps
Cheers
The trusses load bearing is on the exterior walls, In other words they are clear spanned. So no bearing is needed in the center.
For some reason, I was under the impression that any wall stacked on top of another load-bearing wall, was also load bearing.
Thank you all for the responses!
Use under (in place of “on top of”) and you would have the need to continue the bearing to the footing.
The best way to think about it is if structure above is not strong enough to carry its own weight through other structural supports, then the wall underneath becomes load bearing. It is possible to have a load bearing wall that transfers its load to the floor it sits on without a bearing wall right underneath. It is all a matter of design. The graphic you are referencing shows most basic/common design.
Due to the fact that, an architect calculated the interior walls members the arrows point to are not require to be interior load bearing walls due to the fact the exterior wall assemblies have sufficient load bearing capacity to carry live and dead loads of the roof assembly above.
Larry, thanks for the clarification. I think I just flipped the requirements in my head!
The space above the lower truss cord is not habitable, thus no people occupying/walking/storing (hopefully) their crap up there, so there is no weight to bear, so non-load bearing on that wall below. Yes that can change if the trusses are designed for weight carrying capacity, and is being used in that fashion. Just another reason that the truss Certification is required to be available in all homes for reference.
Sample:
Note: All attic trusses do not require a load bearing wall beneath, as they are typically designed for bearing on the exterior walls, as in the example above.
That makes sense! Thank you Jeffery!
If you look at JJ’s drawing the bottom chord is under tension, like pulling a rope in a tug of war. The top chords are under compression (from weight of roof) and pushing out on the ends of the bottom chord (applying tension).
The floor joists below are under compression from the weight above. In the cellar the steel I beam and lally posts support the floor joists in the middle because they are not rated for the complete span across the home. The wall on the first floor provides the same support to the second floor.
Saman, Probably 95% of the time engineered trusses span from one exterior wall to the other exterior wall. BUT, there are exceptions when dealing with extremely long trusses or roofs with complex geometry. In these cases the truss designer can take advantage of some interior walls to make the truss lighter or to fabricate the truss is shorter sections. Some times it’s obvious and sometimes not unless you have access to the truss plans and know how to read them. When in doubt write it up for someone else to make that determination.
Maybe this is over simplistic, but a typical floor is expected to be able to support a 40 pound per square foot load. An attic bottom chord/floor does not have to support a load such as that, therefore there is no need for a bearing wall.
That s correct except as Randy mentions here:
Or, when the 350 pound inspector steps on the middle gusset joint! LOL!
The interior walls on 2nd floor are partition walls and should not touch the ceiling joist of the roof structure. ans the exterior walls are the load bearing units.
Often these are used so the truss can slide up and down. If installed correctly, they won’t affect the drywall joint.
It’s the questions like this that let me know I’m doing right by my clients and explains why 90% of my work is referral based. They want understanding and experience for their $400. Not a test-passer.
Thanks for the validation. No offense.
