Stud size?

[bjochman]

Looking into building a detached garage for storage, shop and potential future "bonus room". The garage is going to have gambrial trusses for a barn look and the room upstairs. What are some opinions on stud size/spacing? 2x4 at 16" centers, 2x6 at 16" centers or 2x6 at 24 centers? Was leaning to 2x6 for insulation purposes in case I do ever finish it, was told usign 2x6 at 24" centers is just as strong, any thoughts?

 

[thammel]

I used 2x6 on 16" centers. Definitely stronger than on 24" centers. I think the point is that 2x6 on 24" centers is as strong as 2x4 on 16" centers.

16" stud spacing is the norm for many other reasons. Carpenters are used to this as even most of their measureing tapes are laid out this way (16, 32,48,64, etc.) If you're going to hang anything from the walls (cabinets?), the 16" will also be advantageous.

I used large attic trusses of a special design. The bottom chord (piece of wood) is 2 x 10". I was glad when the builder had these trusses put on 16" centers too as this made my attic storage area (12" x 32" with 7' ceiling height) even more strong (less floor deflection). This is unusual - typically trusses are spaced on 24" centers - but this is neat now in that the trusses are spaced right on top of the wall studs.

Tom

 

[tcianci]

The 2x6 on 16 inch centers would be your best bet as far as the insulation you can install. Now if the building is not heated, then the thinner insulation in a 2x4 wall would be fine. As far as strength, both spacings are more than strong enough for the compressive loads they will encounter, but the spacing should also be equal to the spacing of your rafters or trusses so that the roof framing falls over a stud, providing a load path to the foundation.The difference is obviously cost and a 2x4 wall on 16 inch centers will provide a generally flatter and less springy wall with respect to any lateral forces than a 2x6 wall on 24 inch centers. Do the numbers, and see what works out the cheapest, fewer but more costly 2x6's or more but cheaper 2x4's and dont forget top and bottom plates too.

 

[IHI]

The only thing we put 24" o.c. are floor joists and trusses, EVERYTHING wall related is 16" o.c. unless other circumstances call for something else.

 

[wadd1]

You also have to consider the ceiling drywall
if you decide to finish
with 24 inch centers you will need 5/8 board
because the 1/2 will eventually sag and look like ****

5/8 is fireboard and considerably more money than regular 1/2

 

[logical]

Without knowing wall height, everything above is a guess. Under 10' high, 2 x 4 @ 16 and 2 x 6 @ 24 is probably an either/or depending on cost and desire for insulation. In many areas..over 10' high will require 2x6 @ 16 minimum.

 

[ddawg16]

5/8's cost me about $1 more than 1/2"

Go with 2x6's on 16" centers....trust me on this....and those 2x6's will give you much straighter walls.....

 

[KenS]

Remember if you go with 2x6s, you need to get doors with deeper jams.

 

[kvom]

Remember if you go with 2x6s, you need to get doors with deeper jams

and windows

 

[marty_p]

Don't EVER consider 24" OC spacings for verticals, horizontals, or ANYTHING -- you'll get what you pay for!

 

[kbs2244]

24 inch spacing of 2x4's is very common around here for detached garages.
16 inch spacing or 2x6's is fine, but it is overbuilding.
I would ask the truss mfg about floor "spring" though.
If you are going to use it for anything other than storage.
Closer spacing and deeper bottom chords with X bracing will help reduce it.

 

[bjochman]

Alright, defenitely will go for the 2x6 on 16" centers, it's only $275 different in cost. Now with that said I'm slightly confused on some statements in this post about the trusses. I thought trusses were always on 24" centers, is this not the case?

 

[nate379]

If you are insulating 2x6 for sure. Even 2x8 wouldn't be crazy. I have seen double 2x6 walls around here even to get 12" of insulation.

 

[porschedude996TT]

If I were to build my shop again, I would have used 2 X 6's rather than the 2 X 4's. The 2 X 6's would have made my wall much straighter. Also the insulation capability is higher. As far as the trusses or cut and stack rafters, I would do it on 16" centers and 1/2" sheeting on the roof and use 5/8" drywall.

 

[kbs2244]

Trusses that are only carrying a roof load are good at 24 inch, even 48 inch, centers.
It is when you are going to add storage loads to them that you have to be careful.
How much weight and if it is going to be "dead storage" or "live weight" (meaning people) has to be considered.

 

[Doug I]

Putting a residential live load on trusses pretty much rules out 2x4 studs even at only 8' walls. 2x6 at 16" would be the first option I'd start at in the design/analysis. Snow and wind loads would determine if 2x6/16 are ok, or you may need to go to 8". Depending upon the span or the truss, occupied area, wall height and the factors I mentioned it's really hard to determine what the stud size/spacing needs to be.

Reference to KBS mentioning storage/live load ..... per Code 'storage' stipulates a 125psf (pounds per sq. foot) load while 'residential live load' is 40psf.

 

[tcianci]

Doug, could you please explain "putting a residential live load on trusses pretty much rules out2x4..etc."

 

[Doug I]

no problem

The Main Wind Force Resisting System (MWFRS) of a building is the framing that resists the external forces applied to the building and supports the internal loads determined by the service of the building.

The external forces are :
1. Wind
2. Snow (blanket and/or drift)
3. Earthquake
4. Retained earth
5. Rain ponding

The internal loads are most often :
1. Dead load DL (flooring, partitions and things that generally don't move)
2. Live load LL (people etc)
3. Service loads unique to that building
4. etc

The International Building Code stipulates minimum values for all of these loads. It's a book about, ohh, 2 inches thick and covers just about everything to do with buildings.

Where the building is determines most of the external forces. Snow loads in Alaska are a little higher than those in Alabama, while coastal wind speeds are higher than inland areas. The IBC defines each of the terms, and has maps showing snow loads, wind speeds etc etc and etc for the US. Wind acceleration due to ridges etc is also covered ... but I digress.

Once I know where a building is I can determine the forces that act upon the envelope of the building. Depending upon the Design Wind Speed a 2x4 stud may be fine, but when a snow drift against it is added to that wind load it may fail, so we can tighten up the spacing or make them bigger.

When we add a floor above the studs are now acting as columns to resist the vertical loads from the floor while still acting as a 'beam' to resist the wind and other horizontal loads. The IBC has pages covering all the different types of rooms that are commonly found and the respective minimum load to be applied to those floors.

A "storeroom" has a minimum live load of 125psf (ok while things that are stored don't often move the load is still called 'live') while a residential floor has a minimum LL of 40psf. A public floor space has a LL of 100, or 150 when it's in a fire egress corridor ... and etc.

Not knowing the geometry of the building in question here, but knowing that it has a floor above it's possible that the vertical load from that floor plus the horizontal loads on the wall may exceed what we call 'unity' for a 2x4 stud. In other words the ration of the sum of the applied bending and axial stresses divided by the maximum allowed for that grade timber is greater than one.

In other words it fails.

It's pretty rare for an external wall supporting a floor to have 2x4 studs.

HTH's

 

[ddawg16]

Or....in simple terms....if it's more than one story....go bigger....

And...the number 16 IS the most important # you will every use.....you'll find out when you start installing shear walls and drywall....ask me how I know.

 

[tcianci]

Doug, wanna run that by me again? You are claiming that nearly every wood frame building is built incorrectly! explain the THOUSANDS of structures that I have either worked in or built that have 2x4 walls supporting upper floors on the first, 2nd and even third stories.

You state:

"It's pretty rare for an external wall supporting a floor to have 2x4 studs."

You're teling me that you have "rarely" seen this construction?

Also there is no such thing as a building that consists only of one wall, wind resistance is a combination of the framing and the frame. Adjacent and intersecting walls either properly wind braced or sheathed with plywood or OSB provide a majority of the wind resistance of a structure.

I know you're using the IBC as your source and I really don't care how thick it is. Because I risk ranting on and telling you that I thnk you have no freakin idea what you're talking about (and i'm not going to say that), will you or anyone else here who obviously understands what I'm not gettnig, explain it to me again.

 

[hmc610]

As a manager at a contractor supply yard that has supplied thousands of homes,garages,comm. bldgs,ect... 99.9% of the time the studs are 2x4 16" o.c. For your garage 2x4 studs would be more than fine even if you had a 2 story garage. Only real reason for 2x6 studs would be for insulation value.

 

[Bevis]

And...the number 16 IS the most important # you will every use.....you'll find out when you start installing shear walls and drywall....ask me how I know.

Okay... How do you know.

 

[Doug I]

whoa there tcianci - simmer down a bit. It's a stud size question for christs sake. You asked me to clarify a comment I made and you seem to be trying to jump down my throat. Nah that ain't gonna happen.

I don't recall claiming a damn thing about buildings being built incorrectly. The OP's question was generic - and I kept my response generic to that. Yup I re-read what I wrote and nowhere did I make that claim - maybe I missed it?

To be boring I'll repeat myself:
but knowing that it has a floor above it's possible that the vertical load from that floor plus the horizontal loads on the wall may exceed what we call 'unity' for a 2x4 stud note I said may exceed not 'does'. I guess I should have added that it's possible that the combine loads may not exceed unity but I really did think that was a little redundant.

Also there is no such thing as a building that consists only of one wall That's why I said right there at the beginning - The Main Wind Force Resisting System system - more than one element, or more than 1 wall.

In referring to the IBC being 2" thick I was trying to inject a little humor into what some could have seen as a 'technical' reply. I don't give a rats patoot how thick it is either - it sits there on my desk getting in the way most of the time.

Of course the cladding on the frame contributes to the global stiffness of the structure - we all know that. It's determining just how much stiffness that cladding adds that is the important question - but not here - the OP's question was regarding stud size.

The forces acting on, and loads supported by a member have a combined effect. The external forces are beyond our control. The building is 'here' hence there are minimum wind and/or snow and/or seismic forces acting on the various parts of the structure. The internal loads we can somewhat control through the frame geometry. We can 'force' a floor load to go 'this wall' by orientating the floor joists in that direction, while the roof loads go to 'that wall' by the same means. That way the loads are shared. There are situations where a wall will carry floor loads and roof loads and wind loads and snow drift loads - and it's then that those combined forces and loads will develop stress that exceed the limits of a certain sized member. If so we make the member bigger. That's what I was meaning tcianci - the combined effects on an individual member that's part of the total system.

A 2-story structure could well have 2x4 studs going the whole way, but those studs will not be carrying enough load to buckle them, or at least I hope the engineer that stamped the drawings has checked that that is actually correct.

Until we know where bjochman's garage is, its dimensions and something about the geometry it's hard to really say how big the studs need to be. If it's 10' to the first ceiling and another 8' to the second floor with 30' floor spans and built in Fairbanks then those studs at 16" centers will be supporting a little over 2000 each. A 20' long 2x4 stud may not do it.

 

[tcianci]

OK, maybe I was too curt with you. The one thing that really made me doubt your whole explanation is that you stated that a 2x4 wall supporting a floor above is a rare situation when in fact it is probably the most common situation that anyone who works in wood frame buildings will ever see.