Stabilizing a tall wall

[grover]

I have a tall wall at the end of my cabin.  It is 24 ft long and about 24 ft tall from floor to peak.  That is 10 ft of lower wall and another 12 ft of the 12/12 pitch gable.  Right now it is just 2x4 studs and osb on the exterior.  Anyway, the problem is it has some wobble when you push on it.  Not a lot but an inch or so looks like a lot when your pushing on it.  I know walls of this size are built every day but I'm not sure what is done to eliminate the wobble.  I have thought about adding two or three 2 x 10's from a parallel inside wall and tie into the outside wall and wrapping it with some rough sawn wood to make it look like a large beam. It would reach 14 ft from the loft to the outside wall.  Another thing I could do would be cut out a 1 1/2 inch spot in the top plate next to another stud and run a long 2x4 from bottom up through the top plate and up as high as possible.  This should help but I think the beam is best.  Hope my explanation is clear.
Any other ideas?

[MountainDon]

That is 10 ft of lower wall and another 12 ft of the 12/12 pitch gable.

I envision 10 foot long 2x4's from the bottom plate up. Then an upper plate running horizontal across those 10 ft studs. Maybe 2 plates? Then 2x4's from that mid wall plate up to the 12/12 pitch slope of the upper gable end.   

Is that more or less the way it is?  Then that movement would be expected.

When you push on the wall diaphragm,or when the wind blows and gusts the wall moves like a drum skin?
No interior walls intersect that end wall to act as a brace?
How many windows? Size? Placement?

This something that is outside the realm of the prescriptive code. Walls like that should be analyzed/designed by an engineer.

A solid interior brace would probably work. It would have to be stout enough to not flex under wind design loads. The wind load can easily reach to 20 PSF, possibly more. In another thread in the last day or so Don_P likened a tall wall to a floor on its side. Think about that for a moment and the size of what would be used as floor joists for spans. Sleeping rooms are usually figured at 30 psf loads for comparison.

Hopefully Don_P will see this later tonight or sometime tomorrow. One thing I know that has been done at times is to place a 2x10 or 2x12 flat as the mid wall plate. That can act to stiffen the wall.

[akwoodchuck]

You're likely going to have to sister on some long 2x4's to your existing studs, tying the two wall sections together and creating a rigid assembly...one on the side of each stud, I would imagine.  Make them as long as you can get from the floor on up (20', probably), and just don't worry about the last few feet at the peak...or add some scabs if you want.  If there's plates in the way, cut 'em out, but only enough to let the sister studs slide in....you'll need those sections for fireblocking.  Sorta like this:  http://www.crodog.org/garage/frameinspect.htm

[MushCreek]

That's similar to the end wall of my barn, which is 28' wide by 22' tall. Mine is framed with 2X6's, and they have been sistered to bridge the joints, but the wall still wobbles. The inspector paid no attention to it, but I'm sure the wall isn't to code. I'm eventually going to put a few beams across to the loft deck, which is fully sheathed, and that should stiffen it up. Another option I considered was a deep shelf across the wall, which would also work, but I didn't want a huge shelf there.

Interestingly, we had a wind storm with 60 mph winds, and I couldn't feel any movement at all, but I still want to brace it.

[grover]

Don, that's exactly the way it is.  No interior walls there and only 2 windows, a single and a double on the dining room end.  Nothing up top.
Chuck, the 2x's sistered onto the existing ones is what I was trying to describe above.  As I said I will have to cut out a 1 1/2 inch long portion of my top plate to slide the long 2x in.
Mush, that's what I will do only with 2x's.  Also a beam running from my loft to the wall meeting it at a 90 degree angle (perpendicular) and anchored well on each end should help a lot. 

Another thing that would really firm it up would be a porch with shed roof on the outside of that wall.  We were leaving that out now so maybe a future project.  That would give me a wrap around porch on that end. 

[Don_P]

Here's where we were on the other thread, I used this as part of a math example there.
http://countryplans.com/smf/index.php?topic=13424.0

A beam across from loft floor to the hinge in the wall will break the top plate span in half.  It would help but would still be insufficient. An interior "plant shelf" beam across the plate zone would help. The end walls and the beam from the loft would be the same as 3 points of support under a girder in the plant shelf scenario.

Tieing a porch roof and ceiling in would work by creating a diaphragm... a thin deep beam to reinforce the wall. It would need to be well connected. The porch ceiling ledger should probably be screwed with oly's or similar structural screws to each stud. That is actually the scenario that finally satisfied an engineer when I got in over my head on one.

[Davegmc]

Is there a loft floor at that end? Seems like the only reason to segment the wall studs on an end wall would be for a floor diaphram. If not, I would really consider adding full length studs oc everywhere except in the shadow of the windows. I believe I read once where Don_P said many jurisdictions even require 2x8 framing in these tall end walls. My inspector wanted as many full length 2x6 studs as possible, and would not let me extend window headers, etc.

[Don_P]

Take a look at table R602.3(5) for maximum allowable stud heights and spacings for typical 90 mph framing.
The max laterally unsupported stud height for a bearing (typically eave) wall is 10'. The max laterally unsupported stud height for a non bearing (typically gable) wall is 14' for a 2x4 and 20' for a 2x6. These are for unbroken, full height, studs.

akwoodchuck mentioned he has had up to 2x12's specced and on the job I mentioned that was what the engineer said he would have specced if I had called him in before I hot dogged it. I had used 2x6's and had built 2 vertical and one horizontal flitch plate beams with 1/4" steel sandwiched between studs and plates. I knew I'd blown it when the wall was still flexible under my fly fart of pushing. He then went on with something else I wasn't thinking about and it relates to thinking about this like a horizontal floor assembly structurally. "You have a few end nails at the top and bottom of these tall studs and we have a large lateral load, do you see the next failure point? The end connections will rip out. I'd like to see framing angles from studs to plates and make sure you have the plates very well connected to the floor and roof diaphragm."

When I've built log homes it is very common to log up to the 8' level and then build a stick framed gable above that with log siding on it... a hinged wall. The log pen below is stiffer than a framed wall but by the time it is punched full of windows and doors the cathedral greatroom wall has 2 rows of header logs, miserably floppy. That was when I started building "plant shelves" at the top plate, basically framing a narrow "loft floor". I would then glue and heavily nail 2 layers of 3/4" ply to top and bottom with seams offset, a plywood box beam. You can find spec papers on the APA website. I've also laid 1/2" steel plate on top of the log wall and lagged it down. I've used a solid sawn 6x12 laid flat as a plant shelf beam inside the wall, that worked well, connection was a bear through the 12" direction. The best was a 10x10 solid sawn beam laid on top of the log wall and then framing above that, looked very nice too. So several ways to skin the cat.

[akwoodchuck]

akwoodchuck mentioned he has had up to 2x12's specced and on the job I mentioned that was what the engineer said he would have specced if I had called him in before I hot dogged it. I had used 2x6's and had built 2 vertical and one horizontal flitch plate beams with 1/4" steel sandwiched between studs and plates. I knew I'd blown it when the wall was still flexible under my fly fart of pushing. He then went on with something else I wasn't thinking about and it relates to thinking about this like a horizontal floor assembly structurally. "You have a few end nails at the top and bottom of these tall studs and we have a large lateral load, do you see the next failure point? The end connections will rip out. I'd like to see framing angles from studs to plates and make sure you have the plates very well connected to the floor and roof diaphragm."

Yeah we used a ton of Simpson LTP5's on the outside of the sheathing, as well as MGT's fastened to the 4x12 corner posts with allthread going down into the foundation, thru the 4x12 PT sill   .....the great room gable had 4x8 king studs at all the windows, with coil strap tying them to the plates.... moral of the story, use lots of Simpson, it makes inspectors go away.....lol. Prow walls, though more complicated, are nice for great rooms, adds a lot of strength.

[Davegmc]

I have a set of plans that shows a great wall gable end wall where there is a 10' lower wall and then the raked gable wall sitting on top of it like Grover's. There is no floor membrane. The wall is stiffened with MST27 straps on the inside of the wall about every other stud. Grover, that would give a big strength and deflection improvement over what you've currently got.

[grover]

I guess I'm not understanding some of your explanations for fixing what I have.   Especially how the Simpson LTP5's or the MST27's are used.  Pictures always help if you have them. 
I thought If I tied the wall to my loft with a beam that would hold the wall steady and I can see how long 2 x 6's from the floor to the ceiling would fix a lot of the drumming.  Basically I've got a hinge point where my bottom wall connects to my upper wall.  I really thought adding a covered porch to the outside of that wall would make it solid.  The roof of the porch would be kind of a shelf on the outside of the wall.  I was hoping the beam would do until the wrap around porch could be added.

I'm going to the property tomorrow so I will take some pics of the wall.

Any other suggestions are appreciated.

[grover]

Check out this guy's wall.  It looks much like mine except his is framed with 2x6's.
http://www.crodog.org/garage/frameinspect.htm
Scroll down to the bottom half of the page.

[Don_P]

Yes, saw it earlier but didn't want to go there. The old adage, just because it's on the net doesn't make it right. The inspector was probably more generous than he could have been, but I'm sure it was stiffer. With 2x4's this would be stiffer than it is but well out of range stiffness/height wise. Notice the roof framing problems as well. Straps on the inside, would help reinforce the hinge. Unless they are tensioned into bowstrings though they won't change the deflection.

[grover]

I only brought it up because it was on of the things that came up when I Googled how to stabilize a wall.  I'm trying to figure out an acceptable fix.

[grover]

MushCreek, I went back doing some searches and found your post (April 19th, 2013) where you had just about the same problem I am having.  You described a fix which is also exactly what I am thinking of doing with beams from your loft to the tall wall.  I didn't see any follow up about how it turned out.  Can you fill me in on the outcome?   

[MushCreek]

I haven't done anything yet. The barn is currently packed full of all of our worldly possessions, as we sold our FL house last month. It would be impossible to work on right now. Plans are to put two triple 2X10's across the 16' span. I'm going triple so I can box them in with 1X wood to simulate large beams in keeping with the size of the room. I'm going to attach them to the loft ledger with 3" angle iron brackets through-bolted. They will overlap the 2X6 framing on the other end, also through-bolted. I'm as worried about the wall being sucked outward as I am about it blowing in. As such, I think it would take a LOT of wind to actually damage it, and we have a dense grove of pines right behind the barn, so the wind tends to blow over the top, rather than hitting that wall with any force.

[grover]

Our minds think eerily alike.   I am thinking of doing just one beam in the middle (14ft) made up of 3-2x10's and maybe some cross beams.  If I put the first cross beam against the wall then I could tie that to the wall also.  If I don't do the cross beams I might do 2 from the loft to the wall.  I don't think mine will get a lot of wind either as we are surrounded by trees.

[MushCreek]

One of the more radical ideas I've had is to put my two beams about 4' apart, and put a bridge across the room. I would put handrails, of course. I want to put a couple windows in the upper gable section, so the bridge would allow access if I wanted to open them in nice weather. Mostly, though, it would just look cool. I could see it all decorated for Christmas. We are supposed to be having fun, aren't we?

[flyingvan]

Would the interior design allow for a diagonal brace running from the ridge somewhere towards the center of the house, diagonally down to a crossbrace in the wall in question ( the closer to the center the better)?
  like this except actually punching through the ceiling to join the wall somewhere

   I'd bet a box of nails Don knows a name for that structural member.

[grover]

The diagonal piece might work but it is a truss ceiling so probably not ideal. 
I had another thought this morning...how about a couple of vertical beams built up of 1-2x8 and 2- 2x12's?  The 2x8 would be in the middle and the 2x12's would be on the outside, flat on one side and a 3 1/2 inch "pocket" on the other side.  The beams would go from floor to ceiling and they would go into the wall and the pocket would wrap around and attach to the 2x4's in the wall.  I would have to wrap the beam with something rustic like rough sawn wood from the local sawmill.  It seems this would look good and make the wall very solid.

What do you think?

[Don_P]

I did something similar on a timberframe SIPs wall. There was a communication breakdown in the order and I had to recut the window openings which messed up the specs on the SIPs.  I think the wall was ~18' wide and ~14' up to a heavy timber rafter tie. The architect ok'ed a triple 2x8 with a piece of 3/8x6" steel sandwiched in the buildup and I made 2 columns that were wrapped in oak to match the timbers. We got some framing angles mounted to the floor and to the oak tie to secure both ends well. Go all the way up to the roof deck not to the ceiling plane of the trusses.

There probably is a correct name for your brace flyingvan, I'd just call it a roof brace... time to drag "Historic English Carpentry" back into the reading room 

there is a log home nearby designed by an engineer friend that has the catwalk to the center of the tall gable wall. I like it. I tried to get one of our clients to let me go from the loft floor, along both side walls and across the end of the greatroom with balconies and bookshelves, a 4' wide U shaped affair, didn't fly but that would act as a pretty good stiffener. Not as good as a full second floor but much better than an open room of tall walls.

[flyingvan]

  The other thought I had last night was, you could put a fireplace against the middle of that wall then frame in a chimney chase covered with sheer panel all the way up.  I'd always rather see fireplaces in the center of the house for heat distribution and optimal draft, but it would serve two purposes here