Tag Archives: roof only building

Skylight Width, Gable Fans, and Post Spacing

This Wednesday the Pole Barn Guru answers reader questions about the standard width of a skylight, gable fans for ventilation, and post spacing for a roof only building.

DEAR POLE BARN GURU: What is the standard width of a skylight on a pole building?


DEAR ROBERTA: In most instances pole building skylights are fiberglass or polycarbonate panels with same configuration as 3′ width net coverage steel roofing. For some extended reading on skylights please visit: https://www.hansenpolebuildings.com/2012/01/skylights/


DEAR POLE BARN GURU: Just completed a 36×84 x 14′ high pole building. Self designed. I sheeted the roof, both gable walls, and the front wall for shear and strength using 1/2″ cdx. I used ice and water shield under the roof and house wrap on the walls. Concrete slab with 6mil vapor barrier underneath. No insulation. Also, no ventilation. Noticing I need ventilation, before things get moldy etc. I’m considering putting a 24″x24″ 5000cfm powered gable fan on the east side, and a 24″x24″ intake vent on the west side. Would this be adequate to keep condensation and moisture at bay? TODD in PORT ORCHARD

DEAR TODD: Lack of ventilation is a harbinger of future condensation problems with well-sealed buildings. Your building has roughly 51,000 cubic feet of interior air volume, meaning a 5000 cfm powered fan will turn your air roughly every six minutes (or 10 times per hour). This should be adequate, however a greater capacity might be worth considering. You will also want to look at actual NFVA (net free ventilation area) of your intake, as lack of intake area can restrict performance of your exhaust fan.


DEAR POLE BARN GURU: Hi, My name is Joe. I’m trying to build a pole barn with in an area of Washington that has a snow load of 15 PSF.  The building is 24′ wide by 38′ deep with 14 feet clear height. no side walls. Seems like spacing varies quite a bit from 8 ft to 12ft. Thought I would see what u would suggest for this?  I was thinking about doing 12 ft or maybe even 10 ft.  Any thoughts would be much appreciated? JOE in WASHINGTON

DEAR JOE: I would look at doing bays of 12′ – 14′ – 12′ first, however you should discuss options with whoever is going to engineer your building plans. Depending upon what you will be using this building for, it may be less expensive to cover one or both 24′ endwalls from roof to ground, than to have a roof only. A Hansen Pole Buildings’ Designer will be reaching out to you to discuss your needs, as we have provided roughly 1000 fully engineered post frame buildings to our clients in Washington State.

Swaying Roof Only Pole Barn

Swaying Roof Only Pole Barn

Yes indeed folks, as probably every owner of a roof only post frame (pole barn) building can and will attest, they sway with the wind.

Reader MIKE in ORLANDO was concerned about his new (not from Hansen Pole Buildings) roof only pole barn moving just from his installing steel roofing panels.

Mike from Orlando writes:

“I just completed the roof panel installation on my open-sided (roof only) Pole Barn structure. It is 38 x 48 with 14 ft eaves. The posts are 8″x 8″x18 ft (4 ft in the ground with full concrete embedment).

While working on the roof I noticed a sway in the structure. As I move around on the roof, the entire roof moves back and forth. It is the poles that are swaying!

This is my first Pole structure (I am self building it from a kit and following the engineered plans).

Is this normal movement? It makes me nervous to walk on the roof – but more importantly, will this be an issue with normal wind forces? Should I add any bracing (like girts between the posts) at the top of the posts to make the structure more rigid?

Thanks for your help.”

Mike the Pole Barn Guru writes:

Your building’s entire roof moves because its columns are working as pure cantilevers – like a diving board. Jump onto an unsupported end of a diving board and even though the board has a well anchored opposite end, the free end flexes. And flexes lots.

Wind (or you installing roofing) causes your building’s posts to act in a similar fashion. Only practical way to reduce or eliminate this will be to cover one or both endwalls from roof to ground with a properly engineered wall (or walls). Unless you truly need to have a just a roof only building, I would recommend you contact your engineer who produced your building’s original plans and contract with him or her to design one or both endwalls for you.

For more reading about roof only pole barns: https://www.hansenpolebuildings.com/2015/04/roof-only-pole-buildings/.