Post Frame Barndominium Exterior Wall Questions
Reader IAN in RIDGWAY writes:
“I am looking for help understanding a couple of exterior wall questions.
- My county is enforcing the 2018 IECC for energy efficiency. In my region this requires R-20 cavity + R-5 exterior wall assembly. From everything I’ve read, this means a continuous layer of 1″ rigid between the framing members and the metal siding. Is this an accurate understanding in your mind? Does the 1″ of rigid between framing and siding affect the integrity of the structure at all? Are the fasteners that are shipped with your kits long enough to accommodate the 1″?
- We will be living in our pole building, which means we will need to meet minimum code standards for receptacles at the exterior walls. I am under the impression that the poles must remain whole and are not designed to have a hole drilled through each for ease of pulling wire. Am I correct here? What is the suggested solution? Conduit everywhere below my slab?”
Mike the Pole Barn Guru responds:
Nice to see jurisdictions enforcing IECC (International Energy Conservation Code) requirements, as it will result in more energy efficient structures. In Ouray County, you are in Climate Zone 6B. This requires ceiling R-49, wood frame walls of R-20 plus R-5 (or R-13 plus R-10) where second value is continuous insulation and slab edges to have R-10 four feet deep.
According to Martin Holladay (Green Building Advisor editor) your continuous insulation is just as effective when installed on the interior of your wall framing. This is very important when it comes to fully engineered post frame construction. Properly engineered, post frame construction relies upon shear strength of steel skin to transfer wind loads through building planes to ground (https://www.hansenpolebuildings.com/2011/12/lateral-wind-loads/). Having rigid insulation between framing and siding would reduce or negate your siding’s shear strength and result in a less than satisfactory outcome. My recommendation would be to use a Weather Resistant Barrier on the outside of the framing, directly inside of steel siding. Fill insulation cavity with unfaced batts (preferably stone wool such a Roxul as it is not affected by moisture https://www.hansenpolebuildings.com/2013/03/roxul-insulation/) or BIBs (https://www.hansenpolebuildings.com/2011/11/bibs/), then a well sealed rigid insulation board between framing and interior finish. Done this way, your wall will ‘dry’ to the exterior, making your home’s HVAC system less responsible for reducing interior humidity levels.
Your wire pulling is far easier than you may have initially envisioned.
Very little drilling, if any, will be needed for holes in order to run electrical wires. Wall framing (girts) extend or are placed so as to leave a 1-1/2 inch space between outside of wall columns and siding.
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.
For practical purposes, a hole up to just less than ¼ of board face being drilled through will be within grade in #2 lumber. Example: 3-1/2” face of a 2×4 a hole up to 7/8” may be drilled through, as often as every two feet. Allowable hole sizes are reduced and spacing increased for higher grades of lumber.
Any holes drilled through pressure preservative treated lumber or columns, especially near grade, should be treated with a Copper Naphthenate solution. Copper Naphthenate is available as a brush-on (Cuprinol No. 10 Copper-Green® Wood Preserver https://www.homedepot.com/p/Copper-Green-1-gal-Wood-Preservative-176223/300502829)
or spray-on(https://www.homedepot.com/p/Copper-Green-Wood-Preservative-14-fl-oz-

Using two inches of closed cell spray foam directly inside steel siding panels not only air seals exterior walls, as it is an effective vapor barrier, but also provides approximately a R-14 level of insulation. Effective applications also require installing form fitted inside closure strips at top and bottom of every wall steel panel – including window and door openings. Closure strips keep spray foam in your walls rather than oozing out and keeps small crawling and flying critters out.
When placing under slab vapor barriers, run up inside of pressure preservative treated splash planks and sealing to top and around columns. Install seal gasket under pressure treated base plate (mud sill) and caulk inside edge to concrete slab.

DEAR KURT: Thank you for your investment in a new Hansen Pole Building – be sure to send me lots of progress photos during construction (and of course ones when it is all complete).
DEAR GREG: Any possible movement would come from either inadequately compacted or loose soil below column footings, inadequate footing diameter, or frost heave. To prevent frost heave, columns footings should be placed at frost depth or deeper and perimeter of slab should be insulated vertically with rigid insulation. In your climate zone, this would entail a four foot ‘tall’ R-10 insulation board. Install on inside face of pressure preservative treated splash plank, with top of insulation even with top of concrete slab. As an alternative, you can insulate slab perimeter per Frost-Protected Shallow Foundation requirements found here (note, slab edge does not have to be thickened or have a stem wall):
DEAR POLE BARN GURU: Hello Guru! We were wondering if the USDA Rural Development program allows for the construction of a pole barn home? KIRSTYN in LANSDALE
Engineered post frame (pole barn) houses rely upon their skin (usually steel roofing and siding) being properly installed to provide diaphragms. When material is placed between horizontal wall girts and steel siding to create a vented rain screen assembly, it defeats your building’s structural integrity, unless structural sheathing is applied to wall girts.
For sake of discussion we will assume you have a dead attic space and will be insulating directly above a finished ceiling. I would ventilate your dead attic space at the eave (air intake) and the ridge (air exhaust). Make provisions for preventing condensation on the underside of roof steel by having some sort of a thermal break. My personal preference is by using an Integral Condensation Control (
For walls – best results will be from two inches of closed cell sprayed to inside of wall steel, then fill balance of wall cavity with either open cell spray foam, or unfaced batts (ideally stone wool
DEAR TIM: Back in my post frame building contractor days we built many a building in and around Medical Lake.
DEAR ANA MARIA: Well, you have reached out to where you should be, as Hansen Pole Buildings specializes in post frame homes (barndominiums and shouses).
My recommendation would be to place a well-sealed WRB (Weather Resistant Barrier) between all wall framing and siding. Use commercial style bookshelf girts to create an insulation cavity
Thank you very much for your kind words. My goal is to see to it people avoid making crucial mistakes so they end up with buildings best meeting their wants and needs, and be as ideal as possible – even if they are not Hansen Pole Buildings.
This myth is created and propagated by post frame kit suppliers and post frame builders who do not understand there is a solution – and a very cost effective one (in both labor and materials).


DEAR JOSEPH: From Hansen Pole Buildings’ Construction Manual, Chapter 2:
DEAR PAUL: I am guessing you are talking about concrete poured for a footing pad under the columns. 
The purpose of a vapor barrier is to stop warm, moist, indoor air from infiltrating fiber-type insulation (think fiberglass or cellulose) during cold weather and condensing. Visible moisture or frost on the inside of a vapor barrier is either caused by a leaky vapor barrier or moisture migrating into the wall cavity from the outside. Leaky siding can cause this, and it often happens in basements that are apparently leak free. Vapor barriers are essential for any kind of insulation that air can pass through. Never do the really foolish act of slashing a vapor barrier that you find has moisture behind it or forgetting to install a vapor barrier in the first place. Today’s best vapor barriers prevent moisture from moving into wall cavities while also letting trapped moisture escape.
Once a ceiling has been installed, blow in attic insulation.