Tall Wall construction

[rwalter]

 Well I am contemplating a last minute design change which is probably never a good idea but here goes. I am building a 20x32 1 and 1/2 story cabin. My design incoporates a steep pitched roof, 17/12, and a dormer on one side.The loft size is 19x20 and on the other end is cathederal ceiling.  Well I am thinking about expanding the dormer so it runs into the cathederal ceiling area of the cabin and adding a dormer on the other side of the roof the same size.  This would basically complete my design and make it the same as the "Providence "design on Johns tutorial.

http://countryplans.com/3dha/Roofs/Providence/Providence.htm

The problem I see is that I already have framed 8 foot walls in place in the area of the cathederal ceilings and the dormers would essentially have two walls stacked on top of one another. Thus creating the potential "hinged wall problem.  I thought to solve this I could use simpson strong ties straight banding irons to strengthen the hinge but I am a little leary. Any suggestions. Whats the maximum height a wall like this can be built and what techniques should be used when framing it. Thanks for the responses.

[DavidLeBlanc]

I'm not familiar with the "hinged wall" effect, but I can guess...

I'll bet you can find a construction adhesive so strong that the wood will fail before the glue line does.

HTH...

[rwalter]

I thought about also taking a piece of threaded rod and bolting the plates together but using glue would be a good idea in addition to the mix.

[PEG688]

  If you haven't sheeted your walls yet , sounds like you haven't, your framed hopefully not sheeted as well  .  You could just apply your sheeting so the break is not at the same place the wall plates are .  You could soldier the sheets, ( apply vertical the sheets to get max break, 4 feet more or less , from the plywood / OSB splice point and the wall plates .)solid block at the break , top and bottom. Hence no hinge effect

  If you are already sheeted some type of strap or maybe threaded rod and some type hold down between the break . Thru bolted thru the studs pulling the wall together  ?? The straps will make drywall or any type interior finish work  a pain

   Where  going to be doing a Prow front place soon and the engineer and I talked about that effect at the windows . He was really good with that as anti hinge effect.   That is here in Washington state , we have lots of earth quake engineering , not sure if that's a issue where you are . Good luck , HTBH  ;)PEG

[PEG688]

I thought about also taking a piece of threaded rod and bolting the plates together but using glue would be a good idea in addition to the mix.

 I didn't peak about the threaded rod idea . I doubt the glue would be considered in this if it's a inspected job .   Only glue they concider a option is epoxy for foundation bolts . A const adh would just be looked at as a good practice but not a silver bullet for a hinge effect problem .

[rwalter]

Unfortunately parts of the walls are sheated but not  100% of it is yet. I might consider removing a sheet or two or at least part of a sheet. Any use of a construction adhesive would be in conjuction with another method of securing the wall. If I go through with this change I am leaning toward bolting the plates together and adding the glue between the plates. I'd also add straps where the sheating is not yet in place or where it is possible with out removing to much sheating. From what I've read on the subject the straping might only be needed every 48". I am in upstate NY so we don't have to worry to much about earthquakes.

[PEG688]

  Out here they go nuts with hold downs , engineering etc .    The flaw with the bolting together of the plates is that without the over lapping of the sheeting ,,,all you have done is bolt the plates together,, the hinge point still is in place . It's a bit wider is all .  If you could do every other or every third as your existing sheeting allows , you'd get a better tie together . Good luck , HTBH  ;)PEG

[John Raabe]

If this is a dormer that is going in where the cathedral ceiling is running (IE: no floor) and you have a double plated wall at 8' then you would like to get the studs to work as if they were full height. This is what you would do if starting over. (Most inspectors let you go 12' high with an unsupported wall).

I would use metal straps to tie the studs above and below the plates. Consider either Simspon H2 ties under the sheathing or something like the MSTC28 that can be installed over the sheathing. That should do the trick.

[rwalter]

John,  

I am a little confused by your post. Yes you described the potential situation correctly. The dormer would continue on into the cathederal ceiling area. Thus there would be no floor in that area. Are you saying the maximum hieght is 12 feet for this? I actually would need the full hieght of the stud of 92 5/8" for this to work.

Here are some screen shots of the design.


http://pg.photos.yahoo.com/ph/webworldcomp/detail?.dir=5d35&.dnm=fcac.jpg

http://pg.photos.yahoo.com/ph/webworldcomp/detail?.dir=5d35&.dnm=23c3.jpg&.src=ph

I tried to post these as images but it didn't work

[John Raabe]

A 12' height limit is what most inspectors have for an unsupported and unengineered wall. You have quite a tall wall there waving around in the wind or earthquake. The floor system stabilizes this of course but that is missing there.

I think I would use cross ties such as double 2x8s on either side of the studs at 48" to tie the opposite walls together. You have some flexibility as to what height you put these.

Put a 2x4 in the middle of this sandwich and you can run wiring and hang fixtures from it.

There are other solutions if you want to talk to an engineer. You could also ask the inspector and maybe they will let it fly. I wouldn't do it where we are, however.

[PEG688]

 Another idea , if you have 2x6 stud walls would be to cut thru your top plates,  both of them, and put a 6x6 post in place up to the under side of a contunous header , like Lindal homes use,, a dbl 2x8 or 10 U shaped header.   Then back frame in your windows / walls between the post .  Keeping in mind span of the header .    Not knowing the overall height you need to get to , It's sort of a guess as to if that is feasible.   The purlin sort of beams John talked about could work but you'd lose the open "feel " .   Just trying to help out    

  Out here we have to block every ten feet for fire . ( No stud bay can be open for more than ten feet.)  We built a Schucks store years ago and used 18 ft . 2x6 studs,, blocked at ten feet for a  exterior party/ fire wall . Of course that more then likely was a engineered wall . To long ago to remember that .   HTBH  ;)PEG

[rwalter]

John and PEG688

Thanks for all the advice. I am not even sure if I am going to follow through and make the changes. .  John yes I had already thougtht about the cross ties I forgot to mention them in my post.  I was actually planning on using either double 2x12x 20 Doug Fir or 2x10x20 Hem Fir at  48" OC  place right at the 8 foot  or 9 foot level from the floor. (I have extra of both on my wood order from the floor joists and roof rafters.) I was planning on doubling them up with a 1/2" plywood spacer glued in between. I like the idea with the placing them on each side of the stud and running electrical lines through them.

While I sit here and type this I feel less inclined to change the original design. One of my objectives of the change was to make the cathederal ceiling area ready to lower to a regular ceiling/floor at some point in the future in case I decide later that I wanted more room upstairs. The other major objective was to make the room feel larger and let in more natural light. Sure I could use skylights but I dislike skylights. They seem to be problematic in this neck of the woods since this area gets a ton of snow and I know a lot of people who have had problems with them leaking and causing ice dams. Just a personal bias against them.  Maybe I be better off building a smaller "pony wall" and place a few smaller windows in this wall. Keep it something less than the 12"  in height, use metal strong tie bracing every 48", bolt the plates and threw in a cross ties at the "future" potential floor height.