Wood

[I-beam]

Does anyone know of any issues of framing a 3-4 story wood framed building with
2x studs and floor framing @ 24"oc, versus 16", if the analysis of the wall
studs checks out for all loads, including lateral
Thanks

 

[phamENG]

If the analysis works, it works. You may need to specify machine graded lumber or engineered studs. To keep it at visual grades, you'll have to work really closely with the architect to keep floor spans manageable. I wouldn't hold out hope for the analysis working part, though. I did a 5 story wood structure and my preliminary design required triple 2x studs at 12" on center for some walls on the first floor...

I can't imagine any constructability issues, but others may disagree.

 

[jayrod12]

Even many of my 3 storeys have 2x studs at 12 by the main floor. Especially for the corridor walls picking up that extra load.

 

[JoelTXCive]

I do not see any issue with it, BUT I would definitely want to be comfortable with estimated axial deflection values of the 1st floor studs.

In my pre-engineering days I walked many 3 story wood structures with 2x4 walls. These were non-engineered homes just built to IRC code. The first floor studs would bow like crazy with the studs at 16" O.C. The homebuilder I worked for switched to 2x6 framing on all the 3 story homes (and they added a bunch of wall blocking).

 

[phamENG]

Also keep in mind the crushing of the sole plates - you can brace your studs all over the place and make them stable while crushing your plates to nothing.

 

[merrittEIT]

I used to do a lot of wood and EWP design. As pham said- if it works, it works. My thoughts would be with the osb bowing at 24 oc and giving the floor too much spring even if your girders are ran at a decent spacing. It's one of those things that is hard to tell through analysis and mroe of a serviceability question. BC Calc (I have no affiliation) offers free web based analysis software to quickly determine things like this. Link to web based software here---> Link

 

[Aesur]

Make sure you look at the fire wall requirements and assembly, many assemblies require studs at 16" o.c. max as well as there is a reduction in strength per footnote m of table 721.1(2) in the IBC. Additionally there are requirements of le/d which tells how to apply the reduction (in some cases you may have to "increase" the height of the wall to check compression, but not bending because of these ratios)- the newer building code appears to have addressed this though. I believe there is also an upper limit of 50 for le/d per NDS.

As noted above, plates become an issue, I have had to use engineered lumber and even 3x plates occasionally to handle crushing as well as if the studs don't stack or have a load path that puts bending on the plates.

Another concern is shear walls, make sure you aren't using a sheathing materiel that requires 16" o.c. max or taking the increase in strength for 3/8" sheathing when spaced at 16" o.c.

 

[Ron247]

My main question is what braces your studs laterally? Solid blocking is all I will accept. I do not accept sheathing unless you can demonstrate it will be there forever.

Saw a 3-story sprinkled building with drywall they claimed braced the studs. No blocking at all. When I asked them if the 1st floor had a fire that the sprinkler put out but ruined the drywall, what was happening next?. Answer, replace the drywall. My answer, you will soon have a 2 story building.

Read the IBC versus IRC. The chart for "minimum stud size" is dangerous in my opinion. Architects use it regardless of the loads. There may not be a structural engineer on the job. If I am correct, one states studs must be braced at 48" OC. The other does not. Where I live, the City bounces back and forth on apartments whether they are to build per IBC or IRC.