Author Topic: My 1.5 story cottage -thinking to balloon frame it. Does it have enough support?  (Read 4566 times)

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Offline walker

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My dad and I are getting ready to build my first house. It is a simple rectangular 1.5 story cottage. We're building it all out of local pine. We're a little unsure of whether to balloon frame it or platform frame it, but it seems like from what I've read on this site that balloon framing would be the way to go (let me know if you don't think so!). Dad has building experience but has never built a balloon-framed house.

Here are our basic plans:


Sorry for the metric measurements...Framing is mostly 2x4" and joists 2x8". Total exterior wall height is about 10 feet, the upper floor joists are to sit at about 8 feet. It will be clad with 1x8" pine weatherboards.

I found this image posted elsewhere on this forum - so I gather the standard process for a building a balloon framed house like this is to run a ledger around all 4 exterior walls and to face nail joists to the stud:


Then I also found this image, which seems to show a different approach for the gable ends:


So what do you suggest for a house like this? Any pointers would be most appreciated!!  ;D

And do we need some kind of additional bracing beyond the collar ties as shown on the plan, to stop the house from bulging out sideways for instance?
« Last Edit: September 20, 2015, 09:36:02 PM by walker »

Offline Ozarkhomesteaders

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Hey Walker.  You could build your house with either type of building.  The platform framing is what I usually do but only because it was the way I was taught, is easier and just the way I know.  I would suggest for some nice reading material on some well done balloon framing to go check out "Our Build In Lincoln Co Mo" on the owner/builder forum.  He has some good pictures of his project he has been working on.
Ozarkhomesteaders

Offline Don_P

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Let's go back to the thinking behind it.
R602.3 ... Studs shall be continuous from support at the sole plate to a support at the top plate to resist loads perpendicular to the wall. The support shall be a foundation or floor, ceiling or roof diaphragm or shall be designed in accordance with accepted engineering practice.

A stud needs to run unbroken from horizontal planes of support. If there is a joint in a stud wall it needs something to stabilize it from buckling under load or wind.

When I can platform frame I do, when that is not possible that is when I fight a tall wall into place. When you do balloon frame it will need to be fireblocked at each floor or every 10' of height max.


Offline walker

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Thank you for the replies Ozarkhomesteaders and Don_P.

Don - we have one concern regarding platform framing it. Should we be worried about the roof trying to push out the top of the upper wall, i.e. where the upper wall meets the rafters?
See red arrows:



I am wondering whether some kind of additional bracing would be required, or whether the boxing-in of the eaves themselves would act as a bracing?

Offline Don_P

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Yes you should be worried about that area, there is no lateral restraint at the top of the wall, balloon framing doesn't really fix that underlying problem. One way is to balloon frame it and extend the floor joists through the wall to form the soffit and tie the rafters to the extended floor joists... forming a stable triangle. Another way is to hang the rafters from a ridge beam sized to support half the roof load. If the ridge cannot sag there is no thrust. Another way is to make the walls on the second floor tall enough that the tie between rafters can be installed in the lower third of roof height, this usually starts working at around 5' high on the kneewalls.

Offline Don_P

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Got back into my P-bucket  ::)
Found a pic of the one way;


Another;


This is a pic off the net I had saved, an old barn with a raised post trying to restrain roof thrust. Over time someone pinned the connection with steel to try to hold it together. Notice the creep deflection in the top of the post.


Taller kneewall and tie dropped to lower third of roof height;


« Last Edit: September 22, 2015, 05:08:36 PM by Don_P »

Offline walker

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Hi Don_P,

We're eternally grateful for your assistance with this! Thank you so much for those ideas - and the pictures - it's exactly what we were chasing. Dad and I have taken a look and we will likely extend the joists out to the rafters near the edges of the eaves. We're amazed we had not thought of this ourselves  d*

Offline Don_P

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I'd use something like the second pic I posted. The next trick is to get the connections up to snuff. On one of the houses I'm working on, 1920's era, it is built that way. The few toenails are tired and there is a lot of split wood at many. I cut plywood gusset plates for each side of the rafter/joist joint, for connection specs it took a little cyphering. First, the codebook heeljoint table, at the end of the rafter span tables, gives the number of nails required in the rafter to joist connection based on building width, roof pitch, and snow load.
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_8_par027.htm?bu2=undefined
For a 20' wide 12/12 building in up to 70 psf snow country 6 nails at each end and at any laps in the joist will resist the tension. They are talking about 16 penny common nails through one 2x and into another. My drawing is stacked rafter on joist and plywood sideplates. We need to create an equivalent or better connection.

The (code approved) awc.org connections calc;
http://awc.org/codes-standards/calculators-software/connectioncalc
is a good place to start.
Set it up in AllowableStressDesign for nails laterally loaded in single shear
To figure out their design strength with 16d commons enter them in SPF 2x's
...120lbs per nail, code called for 6, so they are calling it a 720 lb tension connection. (actual tension in that chord is much higher, code logic  ???... don't spare the nails)

Most people would be shooting a 12d box nail .128x3.25
I'd try 1/2" structure1 ply for the sideplate gussets...66lbs/nail
Try 3/4 ply ...80 lbs. More nails is going to be way cheaper than thicker ply.

Required connection strength was 720 lbs, divide by my 66 lb gun nail = 11 nails. I clamped our gussets on with 2 c clamps and nailed 6 shots from each side into the joist and 6 from each side into the rafter... 24 per rafter heeljoint total.

With that arrangement the ledger could be notched in on the outside of the studs, the compression side. It would be a good wall sheathing nailer there as well.

Seemed like a good idea at the time  :D
« Last Edit: September 24, 2015, 03:35:46 AM by Don_P »

Offline walker

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Don_P - Great info! Thanks for all your help, we'll put up some photos as we progress!