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Advanced Framing, 16-ft. tall wall

user-7346422 | Posted in General Questions on

Hello,

Let me preface by saying I’m not a professional home-builder, rather an owner-builder in the design phase of my first (and likely only) house that I’ll be building.  I have gained a lot of information on this site and I appreciate it, as well as the contributors very much.

The design will be going to engineering very soon, but I’d like to prepare for the likely framing requirements regarding a 16′ tall wall planned in the living room.  The house will be primarily framed 24″ oc with 2×6’s.  Most of it will be 2-story, with the exception of the living room which will be open. 16′ tall walls with vaulted parallel chord trusses (16′ span to outside of exterior walls). Total living room is 16’x18′ (to exterior of walls).

Gable end (16′) will have bigger windows, but side walls (18′) will have windows fitting within 24″ oc studs so their won’t be any breaks in the framing.  Collar ties are spaced every 6 ft which will be wrapped in wood veneer for an exposed timber look.  Sheathing will be structural 1″ rigid foam (Ox SIS, previously Dow), followed by 3/8″ rain screen, followed by 19/32″ LP Smartside panels (also structural) for board batten.

I know 24″ oc 2×6 is not enough structurally. I’m wondering what to expect would be?  Would double 2×6 do it, sistered or spaced 12″ oc? How about single 2x8s?  Or alternately, would staggering 2×4’s 24″ oc offer the same structurally as 2×8’s?  I plan on mineral batt insulation.  Because of the relatively small space, cutting custom sized batting isn’t a dealbreaker, just less than ideal.

Thanks in advance for your help.

Jim

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Replies

  1. Akos | | #1

    Jim,

    You will have to check your local code what is allowed. Here the code tables allow 16' with 2x6 16oc with blocking. The size of the timber/spacing depends really on the snow load and supported roof span.

    One option is to split the wall up into two 8' tall sections. Means adding in extra top/bottom plate in the middle but you can probably stay with your 24"OC.

    1. Andy S | | #4

      This is all speculative and theoretical at this point, so really the only answer is to consult your engineer and let them spec out exactly what will be needed structurally. But since we're just talking here...
      Splitting the wall like that without a floor or intersecting walls could be a potential hinge point. Here in seismic country I doubt it would pass engineering easily.
      Balloon framing that one gable wall isn't out of the question though, it'll just depend on what kind of loads are on it. I just built a 14' gable with a pretty substantial beam above and there were quite a few engineering details that were spec'd but it wasn't anything crazy to accomplish.

      1. Akos | | #8

        Agreed, stacking here is only allowed here for limited opening widths, otherwise tall walls need full length studs.

        Tall walls are very region specific, engineer is the only way to go with it.

        Building them is not too bad, just be ready to spend a lot of time going up/down scaffolding.

  2. user-7346422 | | #2

    Thanks Akos,

    If splitting the wall into 8' sections is acceptable, that would be an easy solution. We'll see what the engineer says. Thanks again for your input!

  3. User avatar
    Peter Engle | | #3

    Splitting the wall into 8' sections is not a good idea. The break in the framing acts as a hinge and makes the entire wall system much weaker. If anything, your engineer may want to go to larger (2x8) studs or engineered studs. You might want engineered studs anyhow, as they are poker straight for their full height. Standard sawn lumber studs are going to be a bit squirrely.

    Your engineer is also going to want to check those collar ties. There is a lot of lateral loading in a tall space like that and some of the loading goes through the collar ties. Every 6' might not be enough, depending on their height, loading, fastening, etc.

  4. user-7346422 | | #5

    I should have mentioned, yes I think I'll be using engineered studs. I also hear you on the hinge effect. The thought occurred to me as well.

    As far as the collar ties, my hope was that 24" vaulted parallel chord trusses could handle the lateral loading. The collar ties are mostly because I like the look, but figured I would mention it because it would add some strength as well.

    Thanks again for your help!

  5. Nathan Scaglione | | #6

    The Wood Frame Construction Manual (WFCM), and supporting books, is the basis for the code and includes both prescriptive and engineered methods. It is superior to reading the code.

    Learn that book inside and out.

    For your first build you're putting yourself on a tight rope. One consideration is dropping the height of the walls in the vaulted area to 10'.

  6. user-7346422 | | #7

    Thanks Nathan. The 16' walls are to match the roofline of the rest of the 2-story house. I'm kind of stuck with it without some major re-design.

  7. Lance Peters | | #9

    I just had my 19'2" tall x 21' wide tall wall Engineered. This is in front of our living room area and is open to the second floor, with large south facing windows.

    The Engineer ended up specifying 5x7 Engineered (Paralam?) load bearing uprights at either end of the headers, transferring loads around the windows. The short (4-6') sections on either side will be split with plates in the middle. The headers attach to the 5x7s with heavy steel U brackets, and the bottom of the 5x7s is anchored into the poured foundation with long fasteners that go through the rim joist area.

    The main concern for this wall (in our area) was wind load. At 400 sqft a little wind goes a long way to generating high forces, and as others have pointed out, my Engineer wanted to avoid having a hinge in the middle of the wall.

    I had originally designed a different proposal for this wall that I feel would have been structurally viable, but I'm building a double-stud wall with an awning roof and the calculations involved would have been more complicated than his eventual, and more conventional, solution.

    At the end of the day the Engineer is liable for the design and they won't do something that makes them uncomfortable. Their solution may or may not agree with your desired outcome, but what they propose should be structurally sound.

  8. Scott Wilson | | #10

    You may discover that in order to have sufficient shear walls you may have to decrease the size of your windows (or lose a couple near the corners). You may have to include steel beams and supports, or possibly a flitch beam. Your engineer will be able to advise you.

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