Stud Walls Between Post-Frame Columns for Alternative Sidings?
Reader JAKE brings up an interesting question:
“Hello! I was looking at the blog for a question I had about wall girts for post frame buildings… I was wondering that if a form of siding is installed on the building other than sheet metal, needing wall sheathing, would it be structurally sound to frame 2×6 walls between your 12’ apart posts and not have wall girts? Just attaching the wall sheathing to the posts and 2×6 walls in between? Thank you!”
Mike the Pole Barn Guru says:
Before we get to your structural question, a few words. 6×6 columns are notorious for having dimensional variability. I have seen them run as much as 3/4″ over dimension. An over 5-1/2 inch dimension would mean your columns are going to project either inside or outside of your stick framed interior wall.
Now we get into structural soundness.
My concern is how to adequately transfer loads from the top of the stud wall into columns.
Walls lie within two wind zones. Zone 5 is within 10% of least building footprint dimension, with a minimum of four feet. It applies to any secondary member with over 50% of its length within this zone. Provided your building is 60 feet or less in length and width and bays are 12 foot, it would not be applicable for your case.
Wind pressure is derived from wind speed “V”. For an Exposure B (protected from wind in all four directions) site, here are applicable loads in psf (pounds per square foot) for secondary components and cladding members (with mean roof height less than or equal to 15 feet) and a fully enclosed building:
MPH PSF (ASD – Allowable Stress Design)
95 10.527
100 11.664
105 12.86
110 14.114
115 15.426
120 16.797
125 18.226
130 19.713
135 21.258
140 22.862
All of these loads are negative, meaning your wall is trying to be sucked out of your building.
Arbitrarily picking 110 mph and a 10 foot wall height (if this is for a residence, or accessory building to a residence, then wall heights are limited to 11’7″ by IRC – International Residential Code Section R301.3):
Total load on a 12′ section of wall (by length) would be: 12′ x 10′ tall x 14.114 psf = 1693.68#. One half of this load is transferred to ground through bottom plate, and one half of remainder must be transferred through top plates to column or 423.42#.
When not nailed into end grain (through a plate into end of stud would be end grain and value is reduced x 0.67; toe-nailing reduces value x 0.83) a 10d common nail (3″ long x 0.148″ diameter) nail has a laterally loaded strength value of 102.022# with Hem-Fir or SPF lumber.
How to attach the wall section to the column is your challenge.
In order to nail through end stud into columns, connection at top of stud (nail driven through top plate) would take 423.42# / (102.022# x 0.67) = 6.19 nails. Probably unrealistic to expect to drive 7 nails into top of a single 2×6 stud.
How about toe-nailing plates to column? 423.42# / (102.022# x 0.83) = 5 nails. While ugly, this might be doable.
Ultimately, connection of top plates to columns would probably be cleanest by use of a Simpson Strongtie strap such an LSTA12.
For our example I have picked a fairly low design wind speed, so higher wind speeds will increase loads and make connections even more difficult. As building mean eave height increases beyond 15 feet, applied loads will increase. In order to meet enclosed building requirements – plan upon use of wind load rated doors (other criteria also apply to meet enclosed requirements), else applied loads may increase. Don’t have a protected site? Exposure C places a load approximately 20% greater than Exposure B on your building.
In summary, while what you propose might work, it should be checked by whatever engineer is placing his or her stamp on your building plans.
This week the Pole Barn Guru answers reader questions about the safety of a pole barn in the event of a tornado, whether a new post frame garage can be added to an existing home, and the standards to run utility wires and pipes through posts.
DEAR SAM: Think of a hole being drilled through as being an “open knot”. Lumber grading rules refer to these as being “Unsound or Loose Knots and Holes” due to any cause. Most structural framing – like wall girts and roof purlins or posts and timbers are graded as Number 2.
DESIGN LOADS/CONDITIONS:
DEAR POLE BARN GURU: It is tornado season again in mid-America and it reminds me to inquire about how best to be survive when up to 150MPH winds hit my ‘prospective’ post-frame house with on-grade slab. What sort of ‘solution’ does the Guru recommend for the SW corner of the house? Here in Zone 6, traditional houses have a concrete basement and include at least a section of reinforced concrete to provide a ‘safe zone.’ Newer houses built on a slab include a reinforced concrete ‘cave’ inside the house which may also be a utilities room. Thanks for any insights you must have since you also know about tornadoes hitting close to home. BRIAN in LE ROY
DEAR POLE BARN GURU: Do you build in the state of Texas. DOUGLAS in MIDLAND
DEAR JASON & ERIN: Your plans did not arrive as an attachment, so I am unable to speak to them. If your concern is with properly pressure preservative columns prematurely decaying when embedded in ground, then Permacolumn Sturdi-Wall Plus brackets are indeed your best design solution. Unlike other, cheaper, brackets, these actually will resist moment (bending) forces and have ICC-ESR approvals as being Building Code conforming. For extended reading on Sturdi-Wall Plus brackets:
DEAR DAN: Every Hansen Pole Building is fully engineered to meet or exceed your jurisdiction’s minimum design wind speed requirements (in Ventura county Vult = 100 mph). When wind is a client concern, we always recommend designing to higher than minimum design wind speeds. In many instances, added investments are minimal. Most important is designing to correct wind exposure for your particular site. Most other providers sell Exposure B rated buildings, when many sites are actually Exposure C. For extended reading on wind exposure, please read: 
DEAR POLE BARN GURU: Would it be possible to install a 1/8- 1/4 ‘’ steel plate C-shaped with a “tail” extending from back side to tie a bottom chord and king post together and then cut out a 6’’ section to allow for a garage door opener install. GABE in SIMCOE
Attached quote is how I would want my own building…..
Mike the Pole Barn Guru’s answers:
Tornado damage in Jefferson City, Mo. as seen on Thursday, May 23, 2019. Photo by David Carson, St. Louis Post-Dispatch.
The entire construction industry can greatly benefit by staying focused on providing framer-friendly details that are easy to understand and implement. It’s critical that we come together with the goal of fostering innovation, using accepted engineering practice, creating installation best practices, working closely with professional framers and assisting building departments to focus inspections on key load path elements. We all are educators. By working together, we will significantly improve the built environment.”
Thank you for your interest in a new Hansen Pole Building. We should be able to take care of all of your needs with a third-party engineer sealed set of blueprints specifically for your building. Face it – this eliminates any guesswork, as anything you do without a Registered Design Professional involved is nothing but a W.A.G. (Wild Ass Guess), probably an errant one. Given height of your roof (it takes full brunt of wind coming from a side) it is unlikely a 6×6 column will work in bending (it is plenty strong enough to support downward forces from building weight and roof snow load acting alone).
In order for this to occur, all jurisdictions should be conforming – requiring Building Permits for structures, RDP sealed plans in order to obtain a structural permit to build, and jobsite inspections to insure conformity to building plans.
DEAR JON:
Since January 1973 anemograph stations within the United Kingdom have tabulated for each clock hour the mean hourly speed and the maximum gust (of approximately three second duration). The ratio of maximum gust speed to the mean speed for individual hours as an effective height of 10 meters is referred to as the gust ratio. The mean wind ration is the ratio of the extreme gust speed to the extreme hourly mean speed, both having a return period of 50 years. This ratio turns out to be 1.60.
Mike the Pole Barn Responds: