balloon framed structure

[troy]

Been daydreaming about my cabin, and keep going through all sorts of options... balloon frame, platform with an attic truss, platform with a pony wall, etc... I was curious about balloon framing and stumbled on this site, which has an interesting description of how it can be done.  In short, it talked about raising and bracing the corner posts, then attaching the ledger, then raising the studs one at a time and attaching to the ledger and toenailing to the sill plate.

The few walls I've framed, have always been on the floor, sheeting attached, then raised and braced.  I was not looking forward to trying this with 12-14' walls, and the procedure described on that site seems like it would be a great way for a single builder.

The question I have, is what downside there would be by toenailing the studs to the sill plate?  Does this impact the strength of the structure at all?  Are there any downsides to putting up a balloon framed structure like this?

I have other questions with regards to balloon framing, but not quite sure how/what to ask yet.

Thanks,

-Troy

[Don_P]

There is nothing wrong with toenailing studs to plates or building walls in place. It is often the best way, your tall walls are one example (I darn near flipped a 17' wall back on us one time and built the next one in place) Basement and garage walls on imperfect slabs are another case where I'll often secure the sole plate, frame the ends, stretch a string to D above middle C and measure for each stud to get the top plate level off an undulating floor. The sheathing actually ties the structure together, in wall framing the choice is between end nails in withdrawal or toenails, neither one is putting the connectors in shear which is the proper way to build strength, that is where connecting it all together with the sheathing does the real work. Gable walls are also often framed in place. You can build tall sawhorses as temporary staging, we've done this while hoisting log walls as well. Don't forget to fireblock at each level or every 10' on tall gables to break up the chimney effect of balloon framing.

As a side note, the 1.5 story balloon frames you see so often on this site with a plate in the middle of the upper gable wall are wrong, the plates should occur at the floor level not in the middle of an unbraced wall. This forms a weak hinge.

[troy]

Don,

Thanks, that makes sense.

Where you mention the gable wall, I assume that you're talking about this:



So, the plate between the upper and lower wall sections should be at the floor, not at the height of the side walls.

---

Next question...

In this photo, the ledger is just a few inches above the headers, wouldn't it be simpler combine the header with the ledger?  Would this have any negative impact on the load bearing capability of the wall?

[Don_P]

Yes, the first photo is of the incorrect framing, the left and right walls are correct, the front and back, gable walls should either be platform framed (to the floor diaphragm) or balloon framed to the rafters (the roof diaphragm).

Sure the ledger can be part of the header, if sized appropriately.

[Two Wheels]

Here's a question that boldly reveals my ignorance...just trying to learn what I can.

Is it possible to have both platform framing and balloon framing on a house that will have a partial loft?  In other words, I'm suggesting a house design that has an open vaulted ceiling in the front area, and a loft in the back.  Can the taller (say, 10 or 12') walls in the vaulted area be constructed of a single stud like balloon framing, with the loft area sitting on the platform of 8' studs, with wall built on top of that to match the same height as the front wall?

[Don_P]

Short answer, sure. Long answer, is probably longer than all the variations I can think of right now but here's what comes to mind right off the bat.
There are maximum stud lengths without engineering, typically 10' for most situations. This is also probably one of the least enforced sections of the code but there still needs to be some careful thought. Do you understand the need to either tie across the lower third of the rafters, or alternatively to hang the rafters from a beam capable of supporting half the weight of the typical roof to prevent outward thrust on either of these walls?

[Cougr67]

I have a question for DonP and Mountain Don:
First off I have the utmost respect for your advice and opinions you share on this site. I do however feel like every time I turn around you are pointing out how others are doing their build incorrectly. From the sample pictures discussed above to balloon framing without support at the top of the wall etc.(like the plans sold on this very site).  I too am wanting to build a 1.5 story cabin with a loft/vaulted ceiling  but I am totally confused about the best and/or proper way of accomplishing this . Is balloon framing not a good idea in general or is it only ok when supporting the roof with a ridge beam or trusses? etc  I will be building in the mountains of Arizona with a 50# snow l load and they are pretty particular about following the building codes and inspections.

This style of cabin is obviously desirable for many people for a variety of reasons. What is the best practice for achieving our desired build both economically and safely and still get sufficient headroom in the loft?

Thanks again for the time and experience you share here

[Ernest T. Bass]

It's just a matter of making sure you don't have top/bottom plates floating unsecured in the middle of your wall. Framing your gable wall to the floor like the graphic here is one way to avoid that, as the OSB floor sheathing braces that potentially "hinge-y" joint.

[MountainDon]

This might ramble a bit...

I grew up in a neighborhood that was built in the late 1800's; a mix of 2 story and 1 1/2 story homes. Our family had a 1 1/2. The stick built roof had the rafters resting directly on the top of the lower walls. It's still there today. That made the upstairs room width about 12 feet I think, on a 20 foot wide lower floor footprint. Sloped ceilings over most of the room, a narrow flat strip down the center. Vertical inner walls ran lengthwise making a triangular space out to the eves. Most of the pictures I see of 1 1/2 floor homes of that era were built like that. There were lots of dormers used to make the upper floor area more spacious. Ours had one where the staircase was and another where the one bathroom was located.

The two story homes were a full 2 stories. I don't know if they were all balloon framed but at least one was. I remember it as there was a fire that gutted one wall. The skeleton with continuous 2x4's from top to bottom was visible until spring when it was rebuilt.    If I do a Google image search today for balloon framing almost all the images that come up are the 2 full story type. The full height upper floor has the rafters placed on the top of the walls making a flat ceiling. Ceiling joists for the upper floor tie the wall tops together. There were afew tall giants; 2 1/2 floors tall. The upper floor on those had slanted walls just like the 1 1/2 's. Nary a "kneewall" in sight.

That same technique of two full height floors with flat ceilings and ceiling joists tieing the rafter ends (and walls) together can be replicated today in either balloon or platform framing and be made fully compliant with today's building codes. The roof structure is structurally the same as in a typical rafter framed single story home; a very strong triangle assembly.

Some time between then and now somebody started building these 1 1/2 floor designs with upper floor kneewalls. I don't know when that became more prevalent or who did them. I can understand the desire for more upper floor space. That was my bedroom for many years. However now I also understand more about engineering principles. I can calculate forces that are involved with the roof loads vectoring outwards on the tops of those wall stubs.

Building codes also evolve over time. Simply put the type of upper floor, walls and rafter built roofs that do not include ties at the wall tops or at the very least ties within the lower third are weak and do not meet code. Most will not fall down but there is potential for sagging ridges and bowed out walls.

There are still many plan books out there with plans for site built trusses. Most were aimed at ag structures from what I have seen. None of them meet current residential codes. Many, maybe most, will come with caveats about checking with the local building authorities for compliance to local enforcement of codes. Plans with roof structures that can not meet present codes can be altered and become compliant. That is where manufactured trusses or ridge beams with column supports come into play. It is possible to build either balloon framed or platform framed homes with half story upper floors with either of those methods.
~~~~~~
Roof truss.
Ridge Beam (most likely also an engineered, manufactured product).
Platform framed short upper walls using raised rafter ties in the lower third. 

One of those, or a combination, is the answer to the question posed, "What is the best practice for achieving our desired build both economically and safely and still get sufficient headroom in the loft?"

Hope that helps.

[JRR]

I'm having a hard time getting my head around why the "incorrect" framing is so incorrect.  True, the sill plate joint will offer a "hinge" opportunity, but just how much "hinging" will happen at the base of the roof triangle anyway ... not much, I think.  And that continuous band of "sill" member, all at the same height around the perimeter, seems to offer a rigid plane that would help keep the sidewalls in place.  Some steel straps applied across the sill joint could offer some hinge resistance if it is a concern.

Having said that, I have always balloon-framed continuously up to the rafters in end walls heretofore.

[akwoodchuck]

For the most part, 'bout the only time we "balloon frame" or build tall walls is in open stairwells adjacent to an exterior wall...almost always topped by roof trusses. Just built one this fall, 36' of 2x12 stud and plate, 4x12 corner posts, 20' tall and sheathed with 5/8" osb....you can bet we built that puppy in place!   A built-up 6x6 post to support a structural ridge beam would solve the problems I see in the pics....

[Don_P]

It might help to think about the wall as if it were a roof or a floor. Instead of snow or furniture as the load, it is wind... ~30 psf is often used for design, the live load for a sleeping room floor is 30 psf, the wind load is fairly significant. The doubled 2x6 top plate at midspan in the gable wall is the girder, the span is 16-24' typically on these cabins. Would you frame a roof or floor with a double 2x6 girder on that kind of span?
I've drawn in the past here a simple fix I've used a few times, a built up horizontal beam spanning that hinge running from wall to wall. Check the mounts at each end of that beam, they are horizontal but no different than posts supporting a typical girder, the load is lateral, the resistance is lateral. Running a vertical ridge support post from floor to roof breaks the span in half, check load and resistance and it may work... think rationally not by guessing, determine load, provide resistance.

from tonight;
http://countryplans.com/smf/index.php?topic=13434.0;topicseen
Let's do a little load math to quantify what we think our bodies are producing compared to what the wind can produce in a full out gale. When VA Tech hooked a football player in a harness up to a scale and had him push or pull he topped out just under 80 lbs of force before losing his footing, they tried several surfaces to give him better traction. In the example above the wall has about 360 square feet of surface. Give the wind 15 psf push or pull at 90 mph, 5400 lbs of lateral load on the wall. What conclusions should we draw when we push on a wall and deem it good enough? In other words, do conclusions about structural capacity of things the size of houses that revolve around "it feels plenty strong" seem rational?

I was not born with any gift, the school of hard knocks is a tough teacher.

[troy]

Been playing with sketchup, slowly getting over the learning curve.  Came up with this drawing:



This is a 16' wide, 8' porch.  The ceiling on the 2nd floor is 8' across and 8' high.  I put a gambrel roof because I really like the look.

What I don't know, is if the 2x6x12 walls and 2x12x16 joists used will be sufficient to resist the thrust from the 2x10 roof.

* For some reason, I'm having problems posting in-line images... maybe post count too low?

[Don_P]

Technically, that is an untied roof and produces thrust. Thrust is a function of load and pitch, this is quite steep which reduces thrust. The shorter the kneewalls and the steeper the lower pitch the better. Correctly the gambrel springs from the floor. Many don't, my barn is a 24' wide gambrel on 18" balloon framed kneewalls framed with the upper tie like yours, my tie is 14' if memory serves, but it is also a barn and not a house.

[MountainDon]

* For some reason, I'm having problems posting in-line images... maybe post count too low?

Post count is fine.

Some image hosting services don't like "hot links" to their images from outside webpages. I'm not familiar with imagebay.us so can't pass judgement on them. However, I did try editing in the img tags and the pictures from imagebay refused to display.

[grover]

Don P or Mountain Don,
Can you explain how a plant shelf is put together or better yet point me to a link where I can see an example?  I've tried to Google it and all I get is how to build a shelf to put my flowers.  I'm still thinking my 2 vertical beams 6 ft apart in the middle of the wall will stiffen it up sufficiently but I haven't done it yet.

[grover]

Ahhhh, I did a little more searching and saw a post from July 2009 where Don_P posted a sketch of a plant shelf.  It looks like short 2x4's tied to each wall stud sandwiched between 2, 2x12's.

http://countryplans.com/smf/index.php?topic=7250.25

Page 2 about 2/3rds of the way down.

[Don_P]

Going back to looking at a wall like a floor with wind causing the load instead of people and furniture... the "plant shelf" is acting the same as a girder supporting a floor. First the girder is sized adequately for the span and load. The next thing to look at is the supports at each end of the girder, where it attaches to the side walls. If you scroll down a couple of posts further in Beavers thread you'll see where I built up columns with 2x8's and steel plate to stiffen a tall gable wall, that was an architect's fix on that job, basically a version of a built up flitch plate girder.