Tag Archives: steel sheathing

Attic Ventilation, Shearwall Stitch Screws, and Adding Sheathing

This week the Pole Barn Guru addresses reader questions about ventilation needed for a new attic with metal ceiling and blown-in insulation, a confirmation for endwall needing stitch screws for shear, and if adding sheathing to an existing pole building would add value.

DEAR POLE BARN GURU: I bought a house with a pole barn that is unfinished inside. The metal walls were not wrapped and the only insulation in the barn whatsoever is double bubble on the underside of the barn roof. I am going to have a metal ceiling put in and then blown fiberglass insulation for an R30 value in what will then be the attic. There is currently no ridge vent nor gable vents either so I am concerned about air flow in the attic once the metal ceiling and blown insulation are complete. The eaves have perforated soffit so I’m hoping even after the blown insulation is done that will provide an air flow into the attic. So am I correct to think that I need to have gable vents put at each end or a ridge vent so that there is positive air flow through the attic? Thanks! BILL in STEVENSVILLE

DEAR BILL: Your thinking is absolutely correct – you need an adequate ventilation exhaust point. Ideally, this would be at your ridge. Gable vents, while meeting code requirements, actually only provide good ventilation immediately closest to vent locations.

This article covers requirements for attic ventilation: https://www.hansenpolebuildings.com/2023/06/274512/

In Queen Anne’s County – you are in Climate Zone 4A. 2021’s IECC (International Energy Conservation Code) specifies R-60 for ceilings in your climate zone. As so much of your cost of blown insulation is having installers show up, you may want to consider going with a greater R value than originally planned. Energy costs are not ever going to go down (nor cost of insulating).


DEAR POLE BARN GURU: I have a rear end wall that is labeled shear wall that says I need an inch and a quarter number 12. Stitch screw 9 and 3/8 on center. Is that every 9 and 3/8 on center vertically on each overlap? DAMINA in TONOPAH

DEAR DAMIAN: You are correct. Panels stitched together have roughly twice as much shear capacity as do unstitched panels.


DEAR POLE BARN GURU: Question for you Guru! I bought a property with a small pole building/shed. Is there any value in adding sheathing? If so, how do you retroactively figure out if the roof will handle the additional load? JESSE

DEAR JESSE: If the roof steel is properly fastened (1-1/2″ screws in flats along one side of each high rib in field, #12 or #14 x 1-1/2″ screws both sides of each high rib at eave and ridge) chances are it will perform admirably without any sheathing. Think of steel roofing and siding as acting like very strong, very thin OSB or plywood.


Purlin Spacing, Wall Insulation, and Roof Sheathing

This week the Pole Barn Guru answers reader questions about purlin spacing for 2×8 that span 17 feet, wall insulation recommendations, and if roof sheathing is needed for a new shop.

DEAR POLE BARN GURU: I need to span 17 feet with 2×8 purlins. Do I need to go 12 inch on center, or can I double 2x8s 24″ on center? Will deck with 7/16 OSB and install standing seam metal roof. BRAD in SPARTA

DEAR BRAD: IRC Rafter span tables are available online here: https://codes.iccsafe.org/content/IRC2021P2/chapter-8-roof-ceiling-construction

Scroll down to Table 802.4.1(1) (this would be for a minimal snow load).

Assuming 2×8 #2 Southern Pine 24″ on center will span only 13’1″ (even 2×10 #2 will only span 16’6″).

Going to a spacing of 16″ on center 2×8 #2 Southern Pine will span 17’1″.


DEAR POLE BARN GURU: Hello, I am looking to insulate the walls of my pole barn and plan on putting up vapor barrier. I insulated the ceiling last year and used Tyvek® basically to hold up the insulation as I can’t afford the steel yet. My question is should I also put up a vapor barrier on the ceiling? Thanks in advance, I appreciate the guidance as this is not my expertise. CHAD in GENESEO

DEAR CHAD: Henry County is Climate Zone 5A.

For your walls, I would recommend unfaced Rockwool either R-30 with a well-sealed interior vapor barrier or R-20 with R-5 well sealed continuous insulation boards on the interior (Comfortboard® 80 or EPS).

As you have under 8000 heating degree days, a ceiling vapor barrier would not be required. Hopefully your attic insulation is Rockwool as fiberglass is affected by moisture and loses R value when exterior temperatures drop. Make sure your attic space is properly ventilated (https://www.hansenpolebuildings.com/2018/03/adequate-eave-ridge-ventilation/).


DEAR POLE BARN GURU: Hello, I am building a 36x50x12 shop with 5:12 roof pitch, that will be conditioned space. The plan is to build out the interior with 2 small bedrooms and a bath then the rest open floor. I am putting in a ceiling at 12′ and will insulate the walls and ceiling leaving the roof uninsulated. Building is located in South Central Texas near La Grange. Does the roof need sheathing and felt or can I just lay the metal roof directly on the purlins? What about adding house wrap to entire building, walls and roof? Being in Texas, heat is biggest factor and with the a/c pumping inside I want to keep attic space vented correctly to keep moisture from building up. I plan to have large soffits to allow for soffit venting then ridge vent on roof. One of my biggest concerns is keeping out all the elements, including creep crawly bugs and concerned the garage doors will be source intrusions. It is my understanding that a sectional garage door is best for keeping out the elements vs roll up type. Can a garage door be truly sealed from all elements including bugs from crawling in? STEVEN in SUGAR LAND

DEAR STEVEN: Roof probably does not need to be sheathed unless your design wind speed is 140 mph or greater (Code requirement) or your engineer specified it. Do NOT housewrap roof, order roof steel with an Integral Condensation Control factory applied. Order raised heel trusses so you can have full attic insulation depth from wall-to-wall. While a sectional garage door is best, there is never a 100% guarantee of keeping crawling critters out – because you are going to open door at some point.

All Steel Buildings Propaganda Part III

NOTE: Today’s blog is part III of a 3 part series – back up two days for the beginning! For those who wish to skip parts I and II, a simple typographical error on the Internet got me to “hansonsteel.com” (Hanson versus Hansen-which is the company I work for) where I found an interesting page on “Steel vs. Pole Buildings”.

For sake of ease of reading, words in italics are those from the all steel building website.


Once your Hanson Steel Building is constructed, it is constructed for a lifetime; the buildings are virtually maintenance free for years.

Pole barns/buildings must have sheeting reattached on a regular basis. And wooden frames for doors and windows will need replacing. Sagging trusses or warped wood framing will cause steel to pull away from the screw connections thus generating water leaks. The leaks in-turn damage the wood construction further. Most pole barns/buildings will need a complete overhaul of sheeting, bolts and screws.

Pole Barn NailIn my thirty plus years, pole building sheeting has never had to be reattached. If proper screws (like those designed for diaphragm design) are used, the manufacturer guarantees the screws will outlast the steel roofing and siding. Companies using nails to attach steel to wood framing – yes, they will come out of the wood creating water leaks and damaging the wood framing. Using screws and the “right” screws as mentioned, stay tight over time due to their design, with the neoprene washer, do not allow water to enter.

I’ve been in all steel buildings which leak.  All steel buildings are often used for commercial & retail uses.  My wife and I frequent a ShopKo in Sisseton, SD. It had numerous leaks in the roof within 5 years of its construction.  The most frequent causes of leaks…in either all steel or wood framed buildings are: use of improper screws, inadequately installed screws, or screws missing the framework.   This retail building had customers walking around plastic covering damaged floor stock due to a leaking roof.  I saw huge dollar signs in looking at the ShopKo building for repairs, not to mention damaged valuable merchandise.  As a customer, it made me a bit leery to even be IN the building, wondering if the roof was going to come down as I watched it dripping into the many “catch” buckets.

The use of vinyl windows and steel jambed commercial steel entry doors eliminates the need for replacement. Prefabricated metal connector plated wood trusses will not sag, and once dried wood framing has been properly installed and fastened in place, warping is not going to occur. Again, I would like to see documentation of ANY pole barn needing a complete overhaul of sheeting, bolts and screws.

Roof and Wall Panels

All Hansen Steel Buildings offer 26-gauge roof and wall panels with strength of 80,000 psi.

Pole buildings are normally produced with a thinner roof and wall panel consisting of 29-gauge steel.

To give a perspective on steel thickness differences, from 29 gauge to 26 gauge the difference in thickness is .0045 of an inch. A sheet of 20# paper measures .0038 of an inch. Roughly speaking the difference between the two gauges is about the thickness of a piece of paper!

Now the important part – how much load will a steel panel carry? The “weak link” in a pole building structure is not the steel roofing and siding, it will be found somewhere in the underlying framing system. Taking a look at the span tables provided to us by American Building Components (ABC) for their Imperial Rib® (Imperial Rib is a registered trademark of ABC) panel, when placed across three equal spans of 24 inches, 29 gauge will support a live load of 124 pounds per square foot (psf) and 26 gauge 141 psf. The difference is only 13.7%!

Bottom line is… do you need 26 gauge steel?  No, you really don’t.  29 gauge is going to do everything you need it to do.  When would you need 26 gauge steel?  If you are going to purchase an all steel building and have 5 feet between your purlins and 7 feet between your girts.  On a wood framed building with half those spacings or less, it’s just overkill.  Beware of those who try to sell you something you don’t really need.

Read more about steel thickness here: https://www.hansenpolebuildings.com/blog/2012/01/steel-thickness/

Fire Rating

Pre-engineered steel buildings offer a Class C fire rating which is the same as masonry buildings. Hanson Steel Buildings are designed for heavy wind, snow, rain or earthquake commercial building codes and provide protection for the building contents.

Wooden pole buildings offer a Class A fire rating which is the lowest resistance to fire hazard. Wooden pole construction cannot be used in many areas where there are stringent building codes for wind, snow, rain, or earthquake.

According to Stephen L. Quarles, Senior Scientist, Insurance Institute for Business & Home Safety, Richburg, SC, “A combustible material will be rated as Class A, Class B, or Class C based on its performance in this test. A material rated as Class A would have a lower flame spread, and therefore a better performance rating, than a Class C material.”

Pole buildings are Code conforming structures and can be designed to meet heavy wind, snow, rain and earthquake design loads. We’ve had clients get permits and successfully construct pole buildings at high snow ski-resorts, in California, Miami/Dade (most extreme wind), New York, Alaska and Hawaii.  In fact, we have pole buildings in all 50 states, including very urban areas. As long as buildings are built to Code, there is no reason anyone should not be able to use post frame construction for their new building.