Mechanically Hung Wall Framing
bluscape
| Posted in General Questions on
I would like to hang my second floor joists inside a framed wall instead of placing them on top of the wall (crown). My mind says the structure will be more rigid if you hang them.
Would it be ok to hang second floor joist on joist hangers on the framed walls?
Why are moist second floor joists placed on top op the wall?
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Replies
bluescape,
Platform framing has evolved to be the way it is for reasons of simplicity, strength and ease of construction. Walls were originally hung from ledgers in balloon framing, but it had so many downsides with no appreciable advantage that it has almost entirely disappeared.
Off the top of my head, the disadvantages of d0ing what you suggest are:
- You have to use much longer studs.
- It will take much longer to do, and be much more difficult.
- Fire-blocking is an issue.
- The loads are now carried on a mechanical connection, rather than supported from below, making the structure weaker.
-The structure doesn't gain any useful rigidity over a conventional one.
- You may have differential settlement between the exterior walls and the interior partitions framed conventionally.
All that said, there are still niche framing methods the use variations on balloon framing. You might want to explore Swedish Framing - which has been featured here in GBA.
Thank you so much for the detailed response. I never really took into consideration the amount of extra material it will require (the longer studs) to hang joists. Therefore I will just stick to a crown. Thanks.
bluescape,
The risk with just doing what is commonly done is 0f course that it stifles useful innovation. But even conventional house building is a fairly complex task, and it's worth carefully picking your spots to do things differently - being sure they yield real benefit, without throwing up a lot of unwanted complexity. A general rule of thumb is that if you don't see something being done, there is often a good reason why.
Good luck with your build.
While I agree with Malcolm that for conventionally-built homes, it's very hard to beat the efficiencies of platform framing, there are other projects where balloon-framing the exterior and hanging the joists on the interior can make sense. We did just that when I worked at a high-performance panelizing company. Balloon framing and hanging the joists on let-in "ribbands" (one of many spellings) is a traditional approach, though stud lengths are limited and may cost more per foot.
What do you plan on hanging them from and how will it be supported? No you should not just nail on a board it needs to be notched into the wall for support getting it perfect take time and skill.
Then you need to install fire blocking slow any fire from spreading from floor to floor getting a perfect seal in every stud bay sounds hard.
If the projects plans need approval this will be a big red flag likely requiring an engineer’s stamp on the plans and extra inspections for fire blocking.
Walta
IRC section R602.3(5) shows the maximum "laterally unsupported stud height" for sizing wall studs. With balloon-framed floors, the floor is lateral support.
Figure R602.3(1), directly below that table, shows on the right-hand side a typical balloon-framed detail.
You are correct that fireblocking would need to be added where the floor meets the wall. I've installed miles of it, it's not that complicated.