Tag Archives: shearwalls

Moisture Barrier for a North Idaho Hanger

Moisture Barrier for a North Idaho Hangar

Reader BILL in SANDPOINT writes:

“Hey guru! Question about insulation – moisture barrier. We are under construction on a 64×70 post frame aircraft hangar in North Idaho. The eave height is 19 feet, plus a two foot heel. There are no overhangs. Roof pitch is 3:12 and the ceiling is vaulted 1:12 there will be a 58 foot wide by 18 foot tall hanger door. Attic venting will be from gable end vents. The roof will be sheathed with 7/16 OSB and receive 30# felt under the 26 gauge PBR. The walls will be sheathed 7/16 OSB and house wrapped under the 29 gauge steel panels. The plan is to install metal liner panel on the ceiling and 5/8″ drywall on the walls. Insulation will be r49 blow in the attic, and r25 unfaced batts in the walls. The hanger door is yet to be determined, but it might also be unfaced batts under a metal liner. Two 125,000 BTU radiant tube heaters will be installed in the ceiling. They will be vented outside and will draw combustion air from outside. I am thinking that it makes sense to install a full vapor barrier for the walls and the ceiling, but would appreciate your thoughts on the matter.”

Mike the Pole Barn Guru writes:

Before we get to your question, I have some concerns….

First – you are putting a 58 foot wide door in a 64 foot endwall. This leaves only three feet of solid wall on each side of your door opening. These areas need to be shearwalls and maximum aspect ratio for a shearwall is 4:1 (four feet of height for every foot of width). With a three foot wide shearwall your maximum opening height would be 12 feet. You are likely to experience some tremendous racking problems (if not a failure) on your door endwall.

Second – trying to ventilate a 4480 square foot dead attic space with gable vents will require 1075.2 square inches of NFVA (Net Free Ventilating Area) in each endwall and this is providing half of NFVA is located in each upper and lower half of each endwall. You could accomplish this with say four 24″ x 36″ galvanized gable vents each end, however this might not be your most aesthetically pleasing design solution. Downside of gable vents is once you get past your first pair of trusses, airflow becomes negligible. I would be much happier with vents in your sidewalls (in area of truss heels) as an intake, combined with continuous ridge venting.

If it were me – I would use unfaced R-30 rockwool batts in sidewalls (they are not affected by moisture and R value does not degrade over time like fiberglass does) with a well-sealed interior vapor barrier before hanging drywall. This would allow your walls to dry to outside. Ceiling should not have a vapor barrier, as you want moist air to be able to escape into your well ventilated attic. I would blow in R-60 of rockwool.

Best of success with your build.

Sometimes There Are Just Not Words: Hansen Building Disaster

Sometimes There Are Just Not Words to Express…  Building Disaster

How horrifically a build can be botched.


In a scene from 2013’s box office flop The Lone Ranger – Tonto (played by Johnny Depp) and the Lone Ranger (played by Armie Hammer) the heroes get themselves buried in the sand up to their necks. After looking at the photos provided by our client of what a “professional” builder did in framing his building, I am thinking tossing a coin to decide the builder’s fate might be appropriate. Heads – buried in the desert to the neck, or tails – boiled in scalding safflower oil (as we would not want the builder to meet his demise due to saturated fats).

These photos are of the front endwall of a Hansen building. The areas where the OSB (Oriented Strand Board) are visible are shearwalls. These are needed in order to carry the horizontal loads imposed on the building due to wind from the roof to the ground. In most cases, the steel siding is adequate to carry these loads. In this particular case, a large endwall door opening precludes this as a design solution.

In order to function as a shearwall the OSB has to be nailed on all edges, hence the 2×6 which is visible on the face of the columns. The engineered plans for this building happen to show the verticals as being 2×4, however this did not stop the builder from hacking up 2×6 which was ordained for somewhere else on the building. The trick to attaching the OSB at the edges (next to the columns) is to mount the provided 2×4 half onto the column, the other half projecting past the column so the OSB can nail to it.

Oops – ignored this part of the plan (and obviously never opened the Hansen Pole Buildings’ Construction Manual where this assembly is shown in step-by-step fashion).

But wait, it gets even better (or worse for the poor building owner)! Stay tuned tomorrow for the next installment .
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Eave Lights in Endwalls

Eave LightsPolycarbonate wall light panels are a very affordable way to get natural lighting into pole buildings which will not have finished interior walls. Most often (and most cost effective) is to install them at the tops of the eave sidewalls.

(For more reading on polycarbonate eave lights: https://www.hansenpolebuildings.com/blog/2011/09/polycarbonate-eavelights-light-up-my-life/)

There are some cases where it would work out better to polycarbonate panels on one or both peaked endwalls.

A caution – eave light panels should not be placed on endwalls below the bottom chord of the end truss, unless significant reinforcement is done to the endwall framing. Eave lights are not designed to be able to transfer shear loads and if placed below the truss, there is a strong possibility they will buckle, crack or fracture. Their failure could cause wind pressures within the building, which it was not designed for, resulting in total collapse.

How would reinforcement be accomplished? By adding appropriately sized steel strapping Xs to the corner bays of the endwall, such as Simpson Strong-Tie CS or CMST: https://www.strongtie.com/products/connectors/cs-cmst.asp

The challenges of using strapping is it must be sized appropriately for the shear loads being transferred to the end of the building, and a significant length of strap must be wrapped around the column at each end, with lots of nails into the column.

So, under what circumstances might “end lights” be appropriate?

When the building is placed so the wall which receives the greatest amount of sunlight is an end. Think of a building placed with eave sidewalls amongst trees, or other buildings which would cause shade.

Another case would be when a side shed or sheds would cause sidewall eave lights to be in the dark.

When adding end lights, the top of the endwall steel panels should be attached to the bottom of the truss, or end truss bottom chord siding backing, with diaphragm screws on each side of every high rib. Z flashing should be placed above the wall steel, then the light panels can be installed with screws every nine inches on center across all horizontal framing.

Keep in mind, any end truss members will “show” through the panels, even though they are most often ordered as opaque white. If end lights are installed below the truss bottom chord and shearwalls reinforced with steel strapping, this strapping will most likely show through the end lights, as well as any wood framing.

With all these considerations, my best advice is always to design a building in such a way the polycarbonate panels for lighting can be placed in sidewalls.