Best Choice For Tall Stud Walls

[KootK]

I've got some 14' 2x6 exterior stud walls. My designer swears to me that they work as 2x6 stud grade @ 8" o/c. Assuming that to be true, and I'll check, is there a practical limit on stud height irrespective of capacity? Should we be using an engineered wood product simply because a straight 2x6 stud grade stud will be difficult to find etc?

Capacity aside, how tall is too tall for regular stud grade stud walls?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[manstrom]

20' is about the max height. It's hard to get anything longer that is not too warped. Over about 10', I'll switch to 2x6s. I have done 2x8s on tall walls as well.

From a code point of view there is a slenderness limit.

2x6@8" o.c. should work fine for a 14' wall. I would switch to (2) at 16" in order to get any electrical through there.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[CANPRO]

I like manstrom's idea of using 2 ply @ 16" instead of single @ 8". Getting straight 2x6 that length isn't too difficult. Back in my house framing days, we would pick the straightest 16' 2x6 for the top plates of the walls...wouldn't have to look through too many to get straight ones. If the framer is any good he is going to discard quite a few to get straight 2x6 for the studs, but not impossible/impractical for a shorter stretch of wall. If this is a long stretch of wall I would consider 2x8 or an engineered product, but if its just a short section of tall wall say in the entrance of a split entry, I would just stick with 2x6. If there are large openings in this wall that may affect your choice as well.

 

[jayrod12]

I've seen guys do 20' tall 2x6 walls.

If the wall is to be insulated see if they work with doubles at 17.5" o/c. Your contractor will love not having to custom cut every batt.

I generally default to 2x8 once I exceed about 12-14 feet.

Is slenderness really an issue if you've got sheathing on the outside and possibly sheathing (drywall) on the inside? I guess in the strong direction it may be but I've never (needed to) ran the number.

 

[CANPRO]

jayrod, that is definitely thinking ahead for the insulation guys with the 17.5" o/c. But the framer will be cursing you when he has to cut every sheet of plywood. I guess you can't keep everyone happy!

 

[jayrod12]

ah, for the plywood you don't have to cut each sheet. It actually ends up working out reasonably well because you've got double studs they only end up having to trim the odd piece to make sure they get a good lap.

I had a really experienced site super on a few of my jobs in a row. He always had little tricks to make peoples lives easier and it taught me a lot about how to save time on a job site. Time is more expensive than material is most cases (Specifically timber framing).

 

[CANPRO]

jayrod, not saying you're wrong here....I'm just having a hard time picturing how the majority of the plywood wouldn't have to be cut.

17.5" does not go evenly into 96", so on a long run of wall I don't see how you can drop full sheets of plywood down and have the joints land on regular stud spacing. I would love to be proven wrong here and learn something new. I think studs at 19.2" is the closest you'll get here.

 

[Canuck67]

If you can get your hands on Tables A-30 to A-33 in Part 9 of the Ontario Building Code, they are tables for tall wall wood studs (with brick, without brick). I sometimes use them as a sanity check. Don't know your wind loading, snow loading and supported tributary width criteria, however, there are instances in the tables of 2x6 SPF No. 1/2 @ 8" o/c (in tables as 2 ply 2x6 @ 16" o/c) being used up to 18' tall.

I have used LSL studs, which are very straight, in tall walls for great room end walls, etc..., however, it can get very expensive doing more than a localized section of wall. For your typical garage/shed type structure, I normally stick with dimensional lumber. My decision on LSL vs dimensional generally depends on the project ... million dollar houses get LSL's, work sheds get dimensional lumber.

 

[Brad805]

Your designer might want to take a look at the energy code before deciding on 8" centers if these are exterior walls. 8" Centers is not practical nor are they very cost effective except for short regions. This sounds a like a case where the designer does not want to change their drawings.

We have done 20'-0" walls in 2x6, but our contractors prefer 2x8 to keep the walls straight above 16'-0" or so. Relatively straight 14'-0" 2x6 studs are easy to find, but the contractor still needs to pay attention to match the stud bow during framing.

 

[Signious]

Nothing too much to add here, good points made by all. I always forget what code you are under kootk, but in most of Alberta stud grade SPF 2x6 is good under C&C loading up to around 18'. Make sure you spec #1/2 or btr for plates if it is a requirement in your area.

Once you hit around 26psf wind loading 18ft or higher goes to an LSL or LVL. Recently I've had lumber yards calling me trying to get MSR spec'd in my tall walls - so that could always be an option for longer 2x8 walls.

 

[KootK]

Yes! Double 2x6 at 16/17.5 it is. There's a bunch of blocking in the wall for weird diaphragm reasons. All the more reason to open up the spacing.

@Jayrod: does insulation need to be trimmed rather than just squishing it in there? Does squishing compromise thermal performance?

@Canpro: a short length wall at a two story entrance space is exactly what this is. Clairvoyant.

@Brad: the "designer" is one of my guys. We can make changes. Excellent point regarding energy codes.

@Manstrom: solid advice obviously. I don't get the electrical part though. Is it that, while you'd have to drill through the same number of studs with 2-ply, it would be done in half the number of operations? Probably a little tough to get a drill and hand in an 8" space too I suppose.


I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

I'm AB too Signeous. We're fairly well represented on here for some reason. I never would have guessed a preference for MSR. I wish that the local framers would publish a live "we prefer this stuff in this order" list online. My predictve powers seem to be pretty close to nil.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

You are not incorrect CANPRO, It's just how it was described to me. It's also a lot less cuts to trim the plywood then to cut all the batts. 19.2" o/c is a spec I've used before, but it is likely in this case that doubles at 19.2" will not work either.

KootK I was told that insulation should not be squished to the point of deformation as it can have an effect on the R-value.

And the electrical part is because it's an absolute bitch to drill holes with an auger bit if the studs are at 8" o/c. The holes end up at weird angles, the wiring doesn't pull nicely and you have to technically fish it through twice as many holes (even though they're half as long).

 

[CANPRO]

jayrod, I've never had the experience of cutting a lot batts to fit, so I guess I can't relate...but I will keep that in mind, thank you. I suppose it would be easier for the framer to nail 5-6 sheets of plywood together and cut a stack to the appropriate length rather than the insulator cutting each batt.

Agreed that squishing the batts isn't ideal. My understanding is that the air space between the fibreglass provides the insulation value, if you squish it out you lose R-value.

 

[Brad805]

Fluffy insulation---> good, tight compressed ---> bad. Buy one bag of insulation and cut about 20 pieces. Immediately after you will appreciate why the insulators do not like to cut it. Spray foam insulation is wonderful, but not too many can afford it.

 

[KootK]

So is insulation available in 24/16/19.2/12 inch strips? This is all new terrritory for me.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

not strips, stud spacings. they're in 22.5,14.5 and 10.5. I don't know if they have them in the 19.2" equivalent or not.

 

[Tmoose]

I believe a decade or 2 back one of the big fiberglass companies claimed 5 or 10% compression was optimum for one of their thermal insulation products, but not the standard residential stuff.

there is a chance I'm mis-remembering acoustic vs thermal performance

 

[medeek]

As soon as I get walls over 9ft I check them and if a DF stud grade won't work I go to a 2x6 DF No. 2. I've only gone to a 2x8 wall once but retrospectively it may not have been a bad idea on a few other projects as well. On tall walls I also specify around windows for a double king stud (2) 2x6 DF No. 2, this is because they are picking up more of the wind load, and in some cases even a triple king stud for a larger window in a tall wall. So two trimmers and three kings, I can imagine the electricians are excited about it.

I've never tried a double 2x6 stud (other than where required for shearwall sheathing panel edges), however in one recent situation I have contemplated it.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[XR250]

I did a church recently where the gable end wall topped out at 29 feet with brick veneer. We used finger joined 2x10's for studs @ 16" o.c.
Seemed to work out nicely. Getting the loads into the diaphragm was a little tough.
14 ft. 2x6's @ 16" o.c. are done here commonly. i usually go to 2x8's over 15 or 16 ft.