Tag Archives: design criteria

Are Building Codes Changed too Often?

(Disclaimer: for those dear readers who are not Christian, the reference to the Bible below is merely for illustrative purposes, and is not an attempt to sway anyone to or from any particular religious practices or beliefs.)

Imagine, if you will, the Bible being revised every three years. Once the revisions were accepted by the scholarly experts and the newest version was printed, each division of Christianity could decide if and when they wanted to adopt the newest version and they could also edit it as they pleased.

Once your church approved a version, it would be up to you and your fellow believers to have to learn it all over again. Sometimes changes would be small, other times large. And about the time you figure it out – there would be another new version.

Sound confusing?

Well, this process is the way the International Building Codes work. Every three years, there is a new version available. Building Officials, Architects and Engineers, as well as builders get to learn everything all over again!

International Building CodeThe NAHB (National Association of Home Builders) and the AIA (American Institute of Architects) have written to the ICC (International Code Council), recommending a longer interval between published Code revisions. The feeling is it would make it easier and less expensive for those affected, as well as easier to manage the changes.

Right now, we have a client who purchased a pole building kit last Spring. When he placed his order, the applicable Code version in his state was the 2009. July 1, his state adopted an amended version of the 2012 Code. He did not apply for his permit promptly, so had to have an entirely new set of plans and calculations produced. Among changes between the versions of the Code, was an increase in design wind speed from 85 to 115 mph (miles per hour)!

While there is some push to increase the time frame between Code versions, it probably will not happen. The reason for frequent changes is the rapid outmoding due to new technologies and building practices.

Think of it this way, a cell phone purchased today will be easily obsolete in three years – same goes for building codes.

What can you do so you don’t end up like our client? Make sure there are no “lag times” between the time you first talk to the building department about what building code design criteria you need to follow, the time you purchase your building, and the time it’s constructed and “final inspection” is done.  And keep in contact with your building department should you encounter any delays.

Building Codes: Wind Exposure C

We all know what Assume Means…

Bob is a builder in Northern California. He made a request for a quote on a building recently, via the Hansen Pole Buildings website.

The building he had in mind was to be 30’ wide x 80’ long. Bob told me the roof snow load was 100 pounds per square foot (psf) and wind speed 60 to 100 miles per hour (mph).

Bob called to discuss the project, which was to have one long sidewall open, so recreational vehicles, tractors and other equipment could be parked. I asked Bob how wide the openings between the sidewall columns would need to be – to which he replied 12’. Quickly doing the math, I suggested he might want to consider 84’ in length, as 12’ evenly divides into 84’. Bob liked that idea.

We discussed wind exposure. I asked Bob, “If you stand in the middle of the building site, with your arms parallel to the ground, and at 90 degrees to each other, and then turned in a circle, would the area between your arms ever be exposed to the wind?”  This would be Exposure C.   The alternative being a site which is protected from the wind on all sides, or Exposure B. Bob advised, once the three walls were up, it would be protected from the wind, because the “local winds never come from the open side”.

Somehow, I just do not think we were communicating.

For once, I listened to the little voice in my head and suggested to Bob that he give me the address of the site and I would call the Building Department to verify the loading requirements. While the building purchaser must ALWAYS confirm the code and loading information with their Building Department prior to placing a building order, I felt an ounce of prevention would be worth a pound of cure in this case.

Now Bob has been a registered contractor in California for over five years, in the area where the building will be constructed. The pleasant lady at the Building Department even guessed who he was, when I gave her the jobsite address. Obviously, he is known, and knows the area.

Well it turns out the design roof snow load was 60 psf, not 100. This will save Bob’s client thousands of dollars. The wind speed requirement is for 85 mph, however the entire county uses C for wind exposure.

There is a moral to all of this. Just because one hires an experienced registered contractor to construct a building, does not mean the contractor necessarily knows or understands the proper design criteria. Having the correct information on loads, saved the building owner thousands of dollars by using the correct snow load, and prevented a possible collapse from using an incorrect (and under designed) wind exposure.

Pole Barn Truss Spacing

What do you mean they aren’t 2 feet apart?

Back in the day (early 1990’s) I was on the National Frame Builders Association (NFBA) Board of Directors. One of my fellow board members from the Midwest wanted to take a peek at how pole barns were constructed in the West, so I invited him out for a tour.

After spending a day looking at several of our building projects, his comment to me was, “The inspectors in our area would never let a pole building be constructed with roof trusses placed every 12 feet”.

Twenty years later, I beg to differ. Hansen Buildings has buildings in each of the 50 states and all of them have roof trusses on what my board member friend would describe as being “widely spaced”.

Modern truss design is highly computerized. Enter the span of the truss, bay spacing and load conditions and the engineering programs will design a truss which will meet the design criteria. The lumber and steel plates the trusses are constructed from, have no idea how far apart they are going to be placed.  They are inanimate! Yet, somewhere in the deep, dark reaches of history, lies the theory wood trusses must be spaced no more than 24” on center, or maybe 48”, or perhaps even eight or ten feet? The reality is, there is no magic number.

Framed Pole Barn

36′ long garage with 12′ bays

While D. Howard Doane is credited with being the innovator of the modern pole barn, it was his Agricultural Service farm manager, Bernon Perkins, who is credited with refining the evolution of the modern pole building to a long-lasting structure.  It was Perkins who pioneered roof purlins being placed on edge. With this design change, roof trusses could be placed 12 feet apart, making it possible for roofs to support the loads to which they would be subjected.

I’ve had roof truss manufacturers try to convince me it is impossible to place wood trusses at spacings of over every 4 feet. Their defense is, “Our engineers will not allow us to”. The manufacturers of the steel roof truss plates (also referred to as gussets or Gang-nails), provide the engineering design for pre-fabricated wood trusses. Their programs will allow for trusses to be placed on 12 foot or even 16 foot centers, and their engineers will place their engineer’s seal on the drawings to verify.

The practicality, cost effectiveness and ease of construction of pole buildings is based upon efficient use of the fewest amount of materials, to do the most work, within safe engineering design. Hundreds of thousands of pole barns are in use today with trusses spaced every 12 feet, or even more. They stand as a tribute to the ingenuity of modern pole building design.