Knee/Pony Wall Framing Question

[rwanders]

Planning a 24x34 1 1/2 story with 10'x24' loft and a 10'x24' balcony. I will frame the 2x6 wall to 12' and this will include a 3' knee or pony wall at loft & balcony to provide more usable space. The roof will be 12/12 with 2x12s and will be built with a 36' 5 1/8" x 16" glulam for the roof beam. The side walls are 2x6 with 7/16 sheathing and board & batten siding. Should I be concerned about the apparent "hinge joint" where the knee wall is attached to the loft and balcony platforms? If so, are there effective methods to reinforce the joint to counteract any "pushing" by the roof? I know I could use some balloon framing at the 2nd floor levels, but would like to avoid that if possible.

Checked out quite a few similar forums----this one is clearly the cream of the crop!!

[glenn kangiser]

If you are using a ridge beam that is properly sized and supported at the ends or as necessary by the engineer, then there should not be outward forces on the walls.  If using a standard rafter system then there are forces pushing out and the semi-balloon framing would be best. 

24' wide is a pretty big roof area and may require design by a local professional if not using a calculated  engineer/architect's design.

...and members like you and others willing to freely share knowledge keep this forum great... along with us chasing off the undesirables. 

[rwanders]

I have consulted both a civil P.E. and an experienced builder and both advised a roof beam--I had originally planned for just a ridge board since my site is somewhat remote and I dreaded getting a crane out there that was big enough to handle a 36' glulam. We had not discussed the knee wall question since I did not plan on one at that time. I feel much more confident now----your counsel is very much appreciated!

[glenn kangiser]

I'm not an engineer or close, but understand loads and work with similar stuff in steel, etc.  If you got similar info from an engineer and builder, then I think you are in pretty good shape.  Eliminating the outward force is why the beam is used but it needs to transfer the force through sufficiently sized posts or headers and posts clear down to the ground in one way or another.

It changes the load from outward thrust (gravity pulling joist centers down - hinging there and wanting to make them longer as they go down - forcing the walls out, as they are what is reacting to the gravity -- pushing back to keep the peak up) to more of a shear on the top beam attachment -- maybe a bit of tension as the joist are held up by the beam, and a compression - or straight downward load on the outer wall rather than an outward force as it no longer has to push the ridge to keep the joists up.  The post supporting the beam are in compression as they are now resisting the loading and transferring it to the ground.

That should be pretty well right -- I don't know about terms for sure but the principals I described should be right.

[John_M]

I will frame the 2x6 wall to 12' and this will include a 3' knee or pony wall at loft & balcony to provide more usable space....I know I could use some balloon framing at the 2nd floor levels, but would like to avoid that if possible.

I know you want to avoid ballon framing, but why?  It just adds so much more stability to your structure and would reduce a lot of the issues you are fearful of.

Also, proper use of collar ties always helps as well.  Lots of info on that subject on this website as well.

[MikeT]

For what it's worth, my place is on a steep slope and 15- 40 miles from the nearest municipalities and I didn't have much trouble at all finding a crane to hoist my glulam to the the ridge of my structure.  I think is was about $200 or so.  Much safer than hand packing.

I should also note that I built using 2x6s with 12' high walls (balloon framed).  A loft sits 8 feet high on the walls and is supported by 6x10 beams.  On one side the beams hang on HUC 610 hangers.  On the other, they rest on  posts that fall between the regular stud bays (I didn't want to lag in a ledgerboard and create a hinge point).

I didn't get a picture of the install, but here is later in the day:



mt

[rwanders]

Actually, I am going to uses a semi-balloon framing system for most of the building. My wall studs won't extend directly from the foundation beam (I will have a sonotube pier foundation)---I intend to use wood I-beams (11 7/8 BCI's)with 3/4 TG for the floor platform. 12' 2x6 walls from there. The only complication for me was the knee wall I needed at the balcony. ..The roof extends out 10' on the front to cover both a first level porch (10x24) and a balcony above that (10x24). With no stud wall between the porch deck and the balcony, I will have to construct a 3' knee wall at the balcony level to support the roof eaves. That was the area giving me pause. My current plan is to mount a 24' 3 1/8x12 glulam on 4x6(corners) & 4x4 posts to form the support beam for the balcony, then using 2x10x10' joists 24oc  running from a ribbon ledger set into the 2x6 end wall to hangers on the glulam. 2x6 decking on top. I intend to frame the 3' 2x6 knee wall from that level to serve as the rafter seat. I will place 4x10's or 6x10's let into the endwall and attached to the glulam using hangers to provide support under the knee wall and lag bolt the bottom plate them to make the joint as stable as possible. These 10' builtup beams will serve as 'headers" between the end wall and the outside balcony supports to carry the balcony and roof eave loads. I have kept firmly in mind the need to always have a clear line of support from loads to the foundation beams and sonotube footings. This forum and the great input from our contributers has been invaluable------they constantly illuminate the complexities hidden in what can seem simple to us newbies! Reading these pages have allowed me to identify numerous "aw shits" in my plans while they can be corrected with my well-worn eraser.

Thanks Guys & Girls!