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Concrete, Steel Gauges, and Skylights

This Wednesday the Pole Barn Guru answers reader questions about volume of concrete needed to support a 300lb sign, pros and cons of both 26 gauge and 29 gauge steel, and replacing skylight panels.

DEAR POLE BARN GURU: I need to know how to calculate how much concrete would support this sign at 10ft with a 6 inch metal pole sign weighs 300lbs. BILL in TACOMA

DEAR BILL: Required amount of concrete will be based upon design wind speed and Exposure where sign will be placed, height of sign above grade and surface area of sign. You would be best served to reach out to a local Registered Professional Engineer, who can provide a sealed design for you (may be required by your permit issuing authority as well).

 

DEAR POLE BARN GURU: For steel roof panels and siding, what are the pros and cons of both 26 ga. and 29 ga. panels? Do the 29 ga. panels have a higher steel yield strength (80 ksi)? TOM in SMITHVILLE

DEAR TOM: Cons of 26 gauge steel roofing and/or siding are added investment and lower steel yield strength (usually 50 ksi or less). For more thoughts on this discussion, please see https://www.hansenpolebuildings.com/2020/11/do-barndominiums-need-29-gauge-steel/

 

Skylight WarningDEAR POLE BARN GURU: We need to replace some sky light panels on one of our older sheds. The roof and current panels are on 12″ center ribs. Do you have sky light panels that will fit my building DAN in ALMA

DEAR DAN: Sadly you are now faced with deterioration issues coming along with fiberglass panels placed in roofs. We provide panels with high ribs every nine inches on center. I would recommend you visit with the ProDesk at your nearest The Home Depot, with exact measurements of your steel profile, as they may be able to order in what you need.

This entry was posted in Professional Engineer, Skylights, Pole Barn Questions, Pole Barn Design, Roofing Materials, Constructing a Pole Building, Footings, Rebuilding Structures and tagged , , , , , , , on by .

Do Post Frame Barndominiums Need 26 Gauge Steel?

Through Screwed Steel Roofing for Post Frame Barndominiums – What Gauge?

If I need to have major surgery, I am probably not going to ask for expert opinions on social media. However apparently, when it comes to construction expertise, Facebook is where to go. Always plenty of armchair engineers, semi-educated builders and competing structural systems to throw out their two bits worth.

American Iron and Steel Institute (AISI) has published accepted measurement standards for steel thickness. 29 gauge steel (post frame industry’s standard) has an average thickness of .0172 of an inch (with a minimum of .0142). 28 gauge steel has an average thickness of .0187 (minimum .0157) and 26 gauge is .0217 (minimum .0187).

These thicknesses are all measured prior to application of any primers or paint.

Steel coil is sold by steel mills or wholesalers to roll formers by weight. Roll formers sell finished formed roofing and siding by lineal foot. Roll formers make the greatest profits by ordering steel coil as close to minimum thickness as possible, as it produces more lineal footage per pound. When roll formers order steel coil, they place orders by minimum steel thickness (e.g. .0145 min would be 29 gauge).

To give a perspective on steel thickness differences, from 29 gauge to 26 gauge difference in thickness is .0045 of an inch. A sheet of 20# paper measures .0038 of an inch. Roughly speaking, the thickness differences between these two gauges is about a sheet of notebook paper! In comparing minimum thicknesses, although a sheet of paper may not sound like much, 26 gauge steel is 31.7% thicker than 29 gauge, based upon minimum thicknesses.

Now more importantly – how much load will a steel panel carry? A post frame building’s “weak link” is not load carrying capacities of its steel roofing and siding, it will be found somewhere in its underlying framing system. Taking a look at span tables provided to us by Union Corrugating Company for their MasterRib® (MasterRib is a registered trademark of Union Corrugating Company) panel, when spanning 24 inches, 29 gauge will support a live load of 112 pounds per square foot (psf) and 26 gauge 150 psf. These differences equating basically straight line with thickness differences.

Unless a building is at a snow ski resort, roof snow loads are probably not going to approach 112 psf, but what about wind loads? The same 29 gauge MasterRib® panel will support 118 psf in wind load, roughly equal to 214 miles per hour! For a perspective, highest officially recorded wind speed measured in the United States was 231 mph. It was logged on 12 April 1934, at New Hampshire’s Mount Washington Observatory at the summit.

But, what about hail? Please read https://www.hansenpolebuildings.com/2020/11/steel-roofing-hail-dents/ and https://www.hansenpolebuildings.com/2020/11/how-to-minimize-possible-hail-damage/.

But, but – oil canning?

Oil canning is a visible, wavy distortion affecting cold-rolled metal products. It’s seen in flat areas of metal panels, and can be characterized as a moderate aesthetic issue. Typically, rippling, waviness, or buckling is especially seen in the broad area of a metal roof or wall.  Most popular 36 inch net coverage, through screwed, steel panels are manufactured with high ribs every nine inches and two low profile ribs in between. These low profile ribs almost guarantee no eye-visible oil canning will occur.


Bottom line is… do you need 26 gauge steel?  No, you probably 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 almost always just overkill.  Beware of those who try to sell you something you don’t really need.

This entry was posted in Roofing Materials, Pole Barn Planning, Steel Roofing & Siding, Post Frame Home, Barndominium and tagged , , , , , , on by .

How to Minimize Possible Hail Damage

Welcome back from Friday’s article. As a fan of long suffering professional sports teams (Vikings, Twins, Mariners) I had the opportunity to watch Randy Johnson’s epic relief appearance in game 5 of 1995’s ALDS.

Randy also helped Geico sell some insurance with this snowball (not quite a baseball sized hail chunk): https://video.search.yahoo.com/search/video?fr=crmas&p=randy+Johnson+throwing+snowball+commercial#id=1&vid=2f0c9212ab8080ee8ad0b4b53361f2a3&action=click

Randy was clocked throwing a 5.25 ounce baseball at up to 102 mph (miles per hour).  A 1-1/2 pound hailstone will travel at speeds up to 105 mph – basically impacting whatever is in its way with nearly 3-1/2 times the force of a Randy Johnson fastball!

At this point in time, there is no solution providing a completely hail resistant roofing solution. No traditional roofing materials can come away from these types of hail stones without being dented or damaged. While there are suitable measures able to be taken to prevent damages from most hailstorms, largest hailstones will cause damage to even the most durable of roofing systems.

In order to understand how well a roofing material will hold up against hail, it is first important to understand how these materials are judged. A common test for measuring roofing material effectiveness against hail damage would be UL 2218: Standard for Impact Resistance of Prepared Roof Covering Materials. This test uses a steel ball to impact various locations on a particular assembly including edges, seams or unsupported joints or sections. While this test provides maybe a best gauge of how a roof will hold up against a hail storm, a steel ball is not a hailstone, and even this extensive test does not guarantee a material or product will hold up against a severe hail storm.

Fortunately, baseball-sized hailstones don’t happen every day. In a majority of instances, a Class 4 UL 2218 rating will be sufficient in protecting your barndominium from roof penetration due to a hail storm. A Class 4 test involves a steel ball weighing 1-2 pounds being dropped from a height of 12 to 20 feet on an assembly’s same location. This is considered by most professionals (and insurance companies) as the highest level of protection a roof covering material can provide.

While UL 2218 (and other testing standards) measures abilities of a material to stand up to rips, tears, holes and penetrating issues, it does not consider a material’s visual appearance once testing is complete. In other words, your roof may still be 100% structurally sound after a severe hail storm, but could also look like someone took a baseball bat to every inch of your roof. Beyond a visual nuisance, some insurance companies who provide a discount for metal roofing will not cover cosmetic damage caused by hail as your roof is still intact and structurally sound.

 To minimize cosmetic damage, take into account panel design. Many standing seam metal roofs have large, flat surfaces showing smaller imperfections due to their smooth uniform appearance. Breaking up a standing seam panel with striations or ribs will help minimize visual impact of dents, as well as help with expansion and contraction in areas prone to temperature swings.

A common misconception when it comes to protecting a structure against hail damage is steel roofing thickness. While thicker steel can be better at preventing dents and surface damage, provided it is not softer, it is also often less flexible than a thinner material.  Thinner steel panels may dent easier, but are less likely to tear. While most metal panels ranging from 22 to 29 gauge steel offer a relatively similar level of protection, there is a difference in how each thickness will perform against different aspects of a hail impact.

An important factor in choosing a roofing envelope able to hold up to most hail storms includes selecting the right underlayment material. Like visible roof coverings, underlayment materials are also tested for impacts. Often people spend a significant amount of time carefully choosing their roof system covering, without ever considering this second layer of defense. Underlayments can not only help protect your barndominium from impact, but are also tested for water, air and fire ratings.

Ultimately there are a number of factors to consider when choosing a roof to help hold up against severe hail storms. Choosing the right materials and speaking to your insurance company about actual coverage of your plan are among the most important choices to make.

Tips for designing a hail resistant roofing include maintaining a minimum roof slope of 6:12 and/or using roof decking (well supported plywood sheathing) and a tested underlayment.

Do your research – speak to professionals about your options, and make decisions on those factors most meaningful to you and your new barndominium.

This entry was posted in Post Frame Home, Barndominium, Roofing Materials, Steel Roofing & Siding and tagged , , , , , , , , on by .

Steel Roofing Hail Dents

When I first began providing Midwest post frame building kits nearly 20 years ago, I was stymied by Michigan clients who were asking for shingled roofs, instead of steel.

Initially, I thought this must be a regional aesthetics thing. My curiosity finally bested me, so I asked about it. Simple answer – fear of steel roofing being damaged by hail! I never would have guessed.

Back then, we dealt with as many as six different steel roll forming companies. My first reaction was to reach out to each of them to ascertain if there was truth to this fear. Only one of them had ever even had a claim submitted to them for hail damage! This certainly seemed contrary to perceptions of pole building clients in Michigan.

Metal roofs are very tough and highly resistant to hail damage.  Hail will not penetrate a metal roof.  Even a new asphalt shingle roof won’t protect a building from a severe hailstorm.  In fact, many metal roofing products have the highest impact resistance and hail rating (Class 4) granted by Underwriters’ Laboratory (UL).  This rating means a product sample did not crack when the same spot was hit twice by a 2-inch steel ball. In a storm, this would translate into a huge hailstone.  As a result of metal roofing’s superior performance in hail prone areas, some insurance companies even provide a reduced rate for buildings protected by metal roofs.

Now and then I read social media posts where potential owners of steel roofing are concerned about hail damage. Pretty well universally builders chime in telling buyers to order thicker steel. But what is actually a better choice, thicker steel or material yield strength?

America’s auto industry has had these same concerns and researched it ad nauseam. Based on testing using practical techniques, empirical formulae predicting force and energy required to initiate a dent have been presented in recent years. Typically:

W = (k * Oy^2 * t^4) / S

where

  • W is denting energy
  • k is a constant
  • σyis material yield strength
  • t is panel thickness
  • S is panel stiffness

Panel stiffness depends upon elastic modulus, panel thickness, shape and geometry and boundary conditions. High strength steels offer more dent resistance at the same thickness as mild steel, or an opportunity for weight saving and equivalent dent resistance at reduced panel thickness.

Let’s look at thickness and yield strength. 29 gauge panels have a minimum bare thickness of 0.142”, 26 gauge panels 0.0187”. Nearly all 29 gauge panels have a minimum yield strength of 80,000 psi. While some 26 gauge panels share this high tensile strength, it is not universal and there is at least one very popular post frame building company roll forming 40,000 psi steel coil.

Let’s explore this formula and effects of thickness and yield.

80,000^2 x 0.0142”^4 = 260.22
40,000^2 x 0.0187”^4 = 195.65

Under these considerations 29 gauge panels are more dent resistant than thicker, softer 26 gauge panels.

For those of you who are not into math, my friends at FBi Buildings have produced this outstanding video: https://www.youtube.com/watch?v=OCTQZXwMIFE

(Hansen Pole Buildings and FBi utilize identical yield strength and thickness steel panels)

Tune in next Tuesday to find out what you can do to minimize potential hail damage for your new post frame building.

This entry was posted in Roofing Materials, Steel Roofing & Siding and tagged , , , , , on by .

What Gauge Steel Do I Need?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: Hi, I came upon your website and found it very well written and informative.  I hope you don’t mind my question, I don’t want to waste your time.  I’m just sort of baffled by steel siding and what I have run across.

To put it as succinctly as I can:

While looking at many companies that provide steel buildings (for me, we’re talking two 20 x 25 foot by 12 foot high “shed” A frames, because my county is very builder unfriendly and they don’t give me a break for agricultural support buildings. Otherwise I wanted a large building), I found that most “popular” online companies sell you 12 gauge steel with a 20 year warranty but will do 14 gauge without a warranty – they’ll only warranty their work, not the metal.

But then I suddenly found a company that was selling 26 gauge steel structures and they DID provide a 20 year warranty.  Finally, I found your site where you explain it all in great detail and you flat out say that typically people debate 26 or 29 gauge but 29 gauge steel is fine.  I am so confused.  It sounds like 26 or 29 is totally strong enough – plus I live in a hot dry area with little wind and no snow so any type of loads are minimal – yet these other folks are telling me I “need” 12 gauge.

Or does this have something to do with whether the building has a wooden traditional frame v.s. a typical steel frame they would sell me?

I’m going to look at what you offer on your site but right now I’m just totally confused by this vast differences in steel gauge.  Thank you for your time.

Best, DRY IN THE DESERT

DEAR DRY: Thank you very much for your kind words.

The 12 and 14 gauge steel buildings are Quonset huts – think if them as being like ants – they have no internal “skeleton”, instead they rely totally upon the steel skin for support. The design of them may or may not meet your needs, due to the curvature of the walls, difficulty to enclose the ends and challenges of condensation control (even in hot dry areas, steel roofing will pose seasonal condensation issues). You might want to read more about them here: https://www.hansenpolebuildings.com/blog/2011/07/quonset-huts/

26 gauge steel structures are most likely an all steel building – structural steel frames and widely spaced steel roof purlins. For buildings of the size you are considering, it is not likely they are an economically viable choice.

The spacing and strength of internal framing members (if any) is going to determine the thickness needs of the steel roofing and siding. Wood frame pole buildings have fairly closely spaced framing members, which lend themselves well to the application of 29 gauge steel.

As you state your county is “very builder unfriendly”, it is highly possible they are going to require RDP (Registered Design Professional – architect or engineer) sealed plans and calculations in order to acquire a building permit. Keep this in mind as you do your building shopping, to make sure whoever provides your new building(s) will be able to supply the correct information needed by your jurisdiction. Good Luck!

Mike the Pole Barn Guru

 DEAR POLE BARN GURU: Hi Mike, I hope I could get your “best guru” advice. I have dug 14 post holes 18 in. x 40in. deep. They fill with water in 16 to 18 minutes. Hole inspection last week did not pass. I read your article on “cookies”,not good?? Do you have any advice on what to do?? Twp. is leaning toward cardboard tubes?? How is a cardboard tube filled with water any better than a dirt hole filled with water?? Thank you in advance. (p.s.barn is 24 x 32 shingled roof) SWIMMING IN SWAMPLAND

DEAR SWIMMING: The first step should be to contact the RDP (Registered Design Professional – architect or engineer) who designed your building, as the ultimate design responsibility rests upon them.

In the event a RDP was not involved with the design – the Building Official now gets to totally call the shots. Sorry, but it the reality – so it may take some convincing him (or her).

In the real life world – Portland cement is a hydraulic cement which means it sets and hardens due to a chemical reaction with water! Consequently, it will harden under water. www.cement.org/basics/concretebasics_faq.asp

When I was constructing pole buildings, we ran into this scenario on an all too frequent basis. You want to place the concrete without incorporating too much extra water. Use a drier than average mix, with less than a three to four inch slump. The concrete should be introduced near the bottom of the pour (if possible). This means using a pump truck so the end of the hose can be placed into the bottom of the hole and pulled upwards as the holes fills with premix. This allows the concrete to rise from below and displace the water out of the top of the holes. This method is done every day, on a plethora of structures, and is usually far superior to “normally” placed concrete because of the available moisture content for proper curing.

If your inspector determines tubes are the “only way” with the idea of keeping the poured concrete out of the water, construct a water tight “cap” for the bottom of the tube, before placing it in the hole.

DEAR POLE BARN GURU: Hi, First off, you have developed an excellent web site which addresses any issue that a person could ever think of regarding post-frame buildings!  Great job.

In one of the blog entries: Evolution of The Pole Barn Guru and his Building Philosophy  Posted by polebarnguru on 06/16/11 @ 8:00 am, there is a mention of the NFBA Design Manual.  I’ve attempted to link to the site, but the manual doesn’t seem to be there.  Would you possibly have an electronic copy of the manual that you could forward me?  Here’s the quote from the blog:

The results of this test are published in the NFBA Post Frame Building Design Manual   https://bse.wisc.edu/bohnhoff/Publications/Copyrighted/NFBA_Design_Manual.pdf

Thanks for the assistance. JUST JEFF

DEAR JEFF: Thank you very much for your readership, as well as your kind words. Like many things on the ‘net, links to articles come and go. Here is a link to the NFBA Design Manual which successfully worked this morning (and can be viewed without having to pay for a subscription – which this particular site suggests): https://www.scribd.com/doc/29750872/Post-Frame-Building-Design-Manual

Mike the Pole Barn Guru

This entry was posted in Pole Barn Questions, Steel Roofing & Siding and tagged , , , , , on by .

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.

Maintenance

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.

This entry was posted in Pole Building Comparisons and tagged , , , , on by .

Steel Thickness: Just When I Think I Have Heard it All

Rachel is one of the Building Designers at Hansen Buildings. This afternoon she sends me an Instant Message.  Here is how it went:

Rachel: “Want to hear a new one?”

Me: “Always”

Rachel: “This customer talked to a local builder about 29 gauge steel and the builder said…

Me: “Drum roll please”

Rachel: …..”Miller makes a beer can thicker than that”.”

Me: “And no, Miller does not make a thicker beer can”

Rachel: “Thought you would get a kick out of that”.

And Rachel was entirely right, as it did get me going. I went on my learning mission for the day and found the average beer can is 80 micrometers thick (to us non-metric folks .0031”). If you have ever tried to smash a beer can on your forehead you can relate to this not being very thick. 29 gauge steel has a minimum steel thickness of .0142”.

Beer cans are also made of aluminum, not steel, with a tensile strength of about 13,000 pounds per square inch (psi). 29 gauge steel has a minimum yield point of at least 80,000 psi.

Whether the builder believes the client would seriously believe this or not, he has made himself look foolish.

The 29 gauge steel used on post frame (pole) buildings by not only us, but virtually every other provider and builder in the country, is over 4-1/2 times thicker and more than six times stronger in tensile strength than the Miller beer can.

Plus, when it comes to spanning capabilities, the calculations are a product of the square of the steel thickness. This makes the 29 gauge steel roofing and siding right about 130 times stronger than Miller beer cans for roofing and siding.

Moral – make a Miller beer can out of 29 gauge steel and try smashing on your forehead. My money is on the can to win!

This entry was posted in Steel Roofing & Siding and tagged , on by .

Let’s Talk Steel Thickness

Three decades ago, when I was a newbie in the pole building industry, I was working in the Willamette Valley of Oregon. One of the local roll formers was selling steel roofing and siding as 26 gauge or (as they called it) .018E.

To begin with, what is a steel roll former? The process of roll forming is one of the simpler manufacturing processes. It begins with a large coil of sheet steel which is fed through an entry guide to properly align the material as it passes through the rolls of the mill.  Each set of rolls forms a bend until the material reaches its desired shape. Roll sets (or dies) are mounted one over the other on a pair of horizontal parallel shafts supported by a stand.

As I am the curious sort, I inquired of this manufacturer, “Exactly what is .018E?” Their explanation was their steel panels would measure as thick as .018 of an inch including the paint! I also found, they were basing their “26 gauge” off the Browne and Sharpe Gauge Chart, which is for wire gauge, not sheet steel. Obviously truth in advertising may have been stretched.

The American Iron and Steel Institute (AISI) publishes the accepted measurement standards for steel thickness. 29 gauge steel (the standard in the post frame industry) has an average thickness of .0172 of an inch (with a minimum of .0142). 28 gauge steel has an average thickness of .0187 (minimum .0157) and 26 gauge is .0217 (minimum .0187).

These thicknesses are all measured prior to the application of any primers or paint.

Steel coil is sold by the steel mills or wholesalers to roll formers by weight. Roll formers sell the finished formed roofing and siding by the lineal foot. Roll formers make the greatest profit by ordering steel coil which is as close to the minimum thickness as possible. When roll formers order steel coil, they place orders by minimum steel thickness (e.g. .0145 min would be 29 gauge).

We found some challenges with this when we had a closely monitored government project which specified 26 gauge steel. We deal with every major roll forming company in the country, and not a single one of them could guarantee their 26 gauge steel as being able to meet a minimum steel thickness of .0187. All of them confessed to ordering 26 gauge as either .018 or .0185 min!

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! In comparing minimum thicknesses, although a sheet of paper may not sound like much, 26 gauge steel is 31.7% thicker than 29 gauge.

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%!

Unless a building is at a snow ski resort, roof snow loads are probably not going to approach 124 psf, but what about wind loads? The same 29 gauge Imperial Rib® panel will support 163 psf in wind load, roughly equal to 252 miles per hour! For a perspective, the highest officially recorded wind speed on Earth was 231 mph. It was logged on 12 April 1934, at New Hampshire’s Mount Washington Observatory at the summit.

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.

This entry was posted in Pole Building Comparisons, Pole Barn Planning, Steel Roofing & Siding and tagged , , , on by .
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