12 foot studs for sidewalls?

[Jared Drake]

I'm sure I've asked this before but I don't remember the answer. Please forgive me. Would 2x6x12' boards be ok for sidewalls if a sleeping loft were going to be built at 7-8 feet? Or would it be better to use some sort of platform framing for the loft?

[MountainDon]

You don't indicate what plans you are using, or the width of the building, etc.

But using tall walls with a loft floor at about the 8 ft height leaves the structure with no rafter ties at the top of the walls the way most folks want to do this. That piece of wall sticking up wants to bend outwards with the weight of the roof and wind and snow loads. It is not a recommended way to build. Is it done? Yes, but that does not make it right. It does not meet building code either.

Better would be to build the walls to 8 feet and place a floor there with the floor joists tieing the walls together. Then build upper walls maybe 5 feet tall. Depending on building width that may give sufficient headroom upstairs when used with rafter ties no higher than the one third point up the rafters. Rafters will likely need an increase in size because of the raised tie. Hope that is clear. If not we can help spell it out. Please give info on bldg width, location or the snow / wind loads and what the seismic zone is.

[Don_P]

Or, the tall studwall, fireblocked between floors, with the roof supported by a ridge beam. This eliminates the need for rafter ties.

[Jared Drake]

I intend to use my Little House Plans. And wouldn't a roof push out on a short stem wall as well? Cabin will probably be around 14 feet wide.

[MountainDon]

. Little House Plans......wouldn't a roof push out on a short stem wall as well? .

Yes, any standard rafter roof with a ridge board, not a ridge beam, exerts a horizontal outward force on the supporting walls. The rafter ties that also serve as the ceiling joists, one at each rafter pair, restrain that outward push when nailed in properly. The problem is when the wall studs are made taller without the ties/joists on the wall tops. The outward force then applies the horizontal force to the end of the extended stud in a manner the stud was not designed for.

As far as I know the Little House plans show 8 foot high walls with ceiling joists / rafter ties on the wall tops and 12/12 pitch rafters connected at the wall top and rafter tie connection.

We do see examples of this use of 'kneewalls' or stem walls used in DIY projects. That does not mean it is best practice.

[Jared Drake]

http://www.pinterest.com/pin/54395107973127234/

There's a link to a pic of what I'm wanting my wee cabin to look like. Suggestions on how to achieve it using the plans I've got?

[MountainDon]

As I suggested previously or Don_P's ridge beam method.

The windows are in the way of a simple ridge beam and columns. There can also be beams and columns to take the load path around the windows. Easiest ridge beam would be to use different windows and take the load straight down each end wall, ridge beam to foundation.   A ridge beam requires a solid foundation to take the roof load; one beam, 2 columns means half the entire roof load on each column. That'll need a good footing and some calcs to size everything. Don_P or I can assist with that.

[akwoodchuck]

Platform frame your second floor, build 5' or 6' sidewalls on top, and scissor truss your roof....that'll give you the desired look, better livability, ability to pass inspection, and no center bearing required (simpler foundation), as well as superior insulation and venting.  All the cool kids are doing it   

[Jared Drake]

Seems like even a scissor truss will want to push those knee walls out. I'm beginning to question whether or not this look is worth the trouble.

[Don_P]

A scissor truss has some deflection but it is minimal, can be designed, and the deflection can be reduced by design. The deflection at design load is provided by the design program when you sit down with the truss designer. He will likely design to the minimums first pass which will give the minimum sized members and max allowable deflection, the cheapest allowable truss. If you don't like it ask him to reduce the deflection. He can do that by lowering the interior pitch or upsizing the members, he'll be spitting out costs at the same time. The most rigid of course is to tie the rafter feet or use a rigid beam to hang the rafters from. With 5-6' kneewalls above you can usually raise the ties to give headroom and still keep them in the lower third of rafter height, this will sometimes require an upsized rafter but generally by the time you have sufficient insulation depth you already have enough rafter depth to handle this. There is also a chart of connections for raised ties, last table in the rafter span tables. Don't raise the ties more than 1/3 of roof height or the spreading forces get too high for the tie connections.

[jhivy]

If it makes you feel better, I'm building what I think you are describing.  Jdhen did too in his "14X36 in Northwest Arkansas" project.

http://countryplans.com/smf/index.php?topic=13308.msg173546#msg173546

http://countryplans.com/smf/index.php?topic=7442.msg95600#msg95600