Wall Stud Sizing Question for Typical Three Story Wood Frame 1

[JonL418]

Hello!

I just have a quick question in regard to a typical three story wood frame project. The building is currently a one story frame with 2x4 (1.5"x3.5") studs at 16" O.C. We are trying to renovate the building by adding another two stories atop the existing one story. What is the best / most efficient way to go about this? adding 2x6 or 3x4 studs to every 2x4? Or to every other 2x4? Or just tear down the entire frame and rebuild using 2x6 / 3x4 studs?

And in regard to the second and third floor, regular 2x4's should be fine for the walls, correct?

I appreciate all insight/ideas/comments. Thank you!

Jonathan

 

[msquared48]

I would sister on additional 2X4's at the first level. The upper floors should be OK with 2X4's, just check the spacing at the second floor - may have to be closer than 16" which will affect the top plate of the first story.

I take it that 2X4 walls are sufficient for the insulation requirements in your area?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JonL418]

What arrangement would you "sister" on additional 2x4's on the first level? And also, how do you come about calculations to see if the spacing for the second floor needs to be closer than 16" O.C.?

The 2x4 walls are sufficient for insulation requirements because it has been an existing one story wood building for a while.

 

[woodman88]

Have you checked to see if the foundation works for the addition loading from the second and third floors you are adding?
If so and it works, then you need to follow the wall requirements in the IRC (or whichever code you are using) or do a calculation for the studs.
If you are looking at 3x4's at 16" oc being required, than adding a 2x4 to each existing 2x4 at 16"oc (assuming they are the required spieces and grade) will work for the first floor.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[dik]

There may have been changes to the code requiring added insulation. I would consider this a major modification to use and occupancy... it's OK because it 'was' is not necessarily a good engineering assessment...

Dik

 

[JAE]

JonL418,
You would simply develop your roof, floor and wall loads, carry them down to each floor, apply lateral C&C wind loads and verify if they work or not. You will need to determine the grade of existing 2x4's and then analyze them when sistered to new 2x studs, allocating load to the existing and new in proportion to their relative stiffnesses. Since you indicated you are a structural engineer, you should be able to do this. This is really not a difficult task.

Another option would be to ignore the existing 2x4's and sister all new studs based on your local code provisions (IBC in the US - section 2308) which should have empirical requirements for studs in walls with three story buildings.

 

[msquared48]

"And also, how do you come about calculations to see if the spacing for the second floor needs to be closer than 16" O.C.?"

This is basic structural engineering. You should know that answer.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[shobroco]

I didn't see a storey height anywhere & I can't size studs without knowing how long they are or what they are carrying. Depending on wind & snow, 3 storeys of 2x4 studs at 8' long can be fine and one storey of 2x4 @ 12' doesn't work.

 

[CANPRO]

I don't like 2x4 for exterior walls.

Sure the 2x4 works for strength (probably borderline at best for getting insulation), but then the plumbers come along and cut a few holes, electricians start drilling..etc...the 2x4 doesn't have a lot of forgiveness with this.

Look at the cost of using 2x6 vs 2x4...very small increase in price compared to the total cost of the job. The potential problems with 2x4 exterior walls aren't worth the savings!!