Tag Archives: OSB roof sheathing

Wall and Roof Sheathing, a Residence/Horse Barn Build, and Animal Confinement Barns

Today’s “Ask the Guru” covers questions regarding the use of sheathing on walls, and roofing with trusses 2′ on-center, if a combo residence/horse barn can be built, and a question asking what the “typical” size of animal confinement barns might be.

DEAR POLE BARN GURU: I am planning to build a pole barn garage with sheathing on walls and roof. Do I need to use purlins on the roof if I use the sheathing instead? The trusses will be 2 ft on center. Thank you, BRUCE in BIG RAPIDS

#12×1-1/2″ Diaphragm Screws

DEAR BRUCE: While there are people who will screw steel roofing directly to sheathing. I would be none of them. Most certainly not OSB, as it will not hold a screw. Personally, I would lay 2×4 purlins flatwise (3-1/2″ face towards sky) on top of sheathing – screwing purlins through sheathing into tops of each truss with structural screws. Then use diaphragm screws to attach steel to purlins https://www.hansenpolebuildings.com/2024/03/thru-screwed-steel-screws/

 

DEAR POLE BARN GURU: Can you put a residential and horse barn together. JARED in WAPAKONATA

DEAR JARED: Absolutely, however there are some considerations to keep in mind:

Dust, insects, rodents, noise and odors.

Fire separation – your jurisdiction may require as great as a two-hour fire wall between these two conflicting uses. You will likely not be able to directly pass between these two, so plan upon an outside entryway.

Insurance will be costly, if even available.

Most clients opt to have these two uses as individual structures.

 

dairy barnDEAR POLE BARN GURU: What are the typical sizes of the animal confinement pole barns? Small and Medium including the doors. GARRETT in PAGOSA SPRINGS

DEAR GARRETT: There are no “typical” sizes for animal confinement as animals vary as much as do their owners. In general, you will find best bang for your investment is multiples of 12′ in width and length.

Sheathing Under Portion of Steel Roof

Sheathing Under Portion of Steel Roof

Loyal and very kind reader JOSEPH in LaPORTE writes:

“Good afternoon, let me start off by saying that I’m extremely appreciative of your content. The reason for my email is that I’ve been contracted to build several 30x180x9 post frame buildings and my plans are calling for 5/8” OSB for the center 60’ of the buildings. Do you have a diagram that shows how to “lower” the purlins 5/8’s to reduce the transition? Thank you in advance.”

Thank you very much for your kind words.

Cases such as yours should always (but rarely are) specified by your building’s Engineer of Record on sealed building plans, but somehow rarely are. Our third-party engineers take it upon themselves to actually account for situations such as these and don’t just leave it up to contractor’s whims to resolve.

Your solution is actually fairly simple – in areas with OSB order trusses with standard 1/4″ heel cuts (vertical ‘butt cut’ on end of bottom chords). For areas without OSB have heel cuts increased by thickness of OSB (in this instance heel cut would be 7/8″). This will allow for all truss carriers to be set to same height and result in a smooth roof plane.

As you have trusses on top of truss carriers, where your transition in heel heights occurs, attach a 2×4 ledger alongside top chord of first 7/8″ heel cut truss (at extreme edges of OSB sheathed area) to support ends of 2×4 purlins laid flatwise.

Somewhat unrelated to your question – I can only assume OSB has been added due to buildings being very long and narrow (aspect ratio is 6:1). If this is indeed your situation, then steel roofing by itself is unlikely to be able to carry applied shear loads. However, greatest shear is at each endwall, not at center of roof. I would have expected to see a need for OSB closest to each end, rather than in center 1/3rd. You might want to point this out to buildings’ engineer as (given information at hand) it could prove to be a serious design flaw and could potentially result in a failure situation under extreme wind loads.