Tag Archives: engineered pole building

Engineered Pole Barn

This is Why Pole Barns Should be Engineered

A line of strong thunderstorms moved through North Central Florida Saturday March 23, prompting severe thunderstorm warnings and a tornado warning.

The photograph is of the remains of a pole barn, which is suspected to have been hit by a tornado. No other structures in the area were destroyed, however there were reports of severe hail damage to the siding and windows of one manufactured home.

Luckily the eight horses who were housed in this barn survived.

fallen pole barnOf course I am not able to personally visit the site to examine the damage forensically, however I can make some observations, which leads me to suspect this particular destruction was as much due to poor design, as it was to having been hit by high winds. If it had been an engineered pole barn, my educated guess is the damage might have been been minimal, if not “fixable”.

Look first at the building columns – leaning every which way. They did not break off from the wind, but are in pretty much every direction other than being plumb. This tells me they did not have any concrete around the bases of the columns, which would have kept them upright.

The columns are notched on the outside – which is a sign there was once a truss carrier (a beam from column to column to support the trusses) in the notch. As no truss carriers are yet in place, the connection between the columns and the truss carriers was obviously inadequate to withstand the uplift forces.

Connections are always the weak link in any structure. Every once in a while, the History channel will show a segment on building failures – and it is nearly always the fault of under designed, or under sized connections.

While a properly engineered pole barn may not have survived the full onslaught of a direct hit from a tornado, the chances of damage being minimal would have been far greater had a registered design professional been involved, and his or her plans followed.

Don’t take unnecessary risks with valuable property and animals.  Seat-of-the-pants design is rarely adequate.

Building Engineer: One Who Should Know Better

Over the years we have provided, to clients, several post frame buildings in a county in California which will remain unnamed in this blog.

This particular county has an actual registered building engineer who does the structural plan reviews.  Sometimes this can be a good thing, sometimes a challenge.

One of our clients recently submitted a plan (produced by one of our engineers and including all of the calculations) for a new barn. This particular building had a wood floor, supported by floor joists. The floor joists were attached to gambrel (old barn profile) roof trusses at each end, by joist hangers. The sidewall columns (and trusses) were spaced at 12 foot on center. The greatest distance spanned by the 2×10 #2 floor joists is 11’8”.

The building engineer who did the review came up with:

“Please take another look at the 2×10 floor joists. Using a live load of 40 psf, which may not be

applicable if the area is used for storage, #2 DF fail in bending. #2 Hem-fir is even worse.”

Now the lovely thing about the International Building Codes is the span tables listed in Chapter 23 for things like – floor joists!

It really does not take rocket science for the average lay person to look at Table 2308.8(2), “Floor joist spans for common lumber species”. The table lists Douglas Fir-Larch, Hem-Fir, Southern Pine and Spruce-Pine-Fir. Going down the 2×10 column, to the 24 inch joist spacing area, lets the reader know the least span for any of these species, in #2 grade, is 12-5.

NDS BookIn the event the building engineer did not choose to open the code book, there are free online resources which can be accessed. The American Wood Council has a very handy one at www.awc.org, which I use frequently.

My real peeve here – this plan check has now created unnecessary work for our engineer, and creates skepticism in the client’s mind.

Oh, by the way, our engineer had provided the calculations which prove the floor joists specified do work, the reviewing engineer neglected to look through them!

Should You Invest in Pole Building Engineering…or Not?

Clients ask me, “What is the difference between your engineered and non-engineered buildings”? In the case of Hansen Buildings, the only difference is the engineered buildings have been reviewed by a professional engineer, who is registered in the state where the building is to be constructed. This review is for structural adequacy.  And, following the review, plans and calculations are printed originally wet sealed by the engineer.

From a practicality standpoint, what pole building engineering is… is insurance. Insurance? Yes, it means a registered design professional verifies the building design will work and withstand the forces of nature up to the levels specified on the building plans.

There are some pole barn providers who do make structural changes to their buildings depending upon whether the buildings are engineered or not engineered. Morally and ethically, it is this author’s opinion there should be no changes in material design whether an engineer seals the plans or not. If changes ARE needing to be made, it could lead one to believe the non-engineered buildings are under designed and could fail within the load parameters the buildings should have withstood!!

While I do not agree with this practice, many Building Departments will issue pole building permits without engineered plans. In some cases, permits are issued with no plans being submitted at all!

Regardless of Building Department policy, any building used for commercial purposes should include “sealed” plans with pole building engineering.

Many Building Departments have “prescriptive requirements” for non-engineered post frame (pole) buildings. What are “prescriptive requirements”?  If you construct your building to match what their specifications are, they will issue you a building permit. Rarely are these requirements economically practical from either a materials or labor standpoint. Almost universally, it will prove less expensive to invest in a fully engineered building kit, rather than following the prescriptive requirements. Colorado and Washington are two states in which Building Departments often hand out these requirements.

Any building in Arizona, California, Florida, Oregon, Nevada, Utah or Washington which requires a Building Permit which includes a structural plan review (pretty much a guarantee), should have engineered plans.

If prefabricated trusses are used, the company manufacturing the trusses will provide engineer sealed truss drawings. The truss engineer is NOT the Engineer of Record for the building, nor does this make the building itself engineered.

The International Building Codes, on their own, do not have specific prescriptive tables for post frame building components – unlike “stick built” buildings. Even stud wall framed buildings are required to be engineered when the walls are over 10’ in height.

In the 2009 version of the Codes, is a new twist. Any buildings of 60′ or greater clearspan REQUIRE the end user to hire a Registered Design Professional (engineer or architect) to provide special inspections to assure truss bracing is properly installed.

Don’t underestimate the value of pole building engineering. The engineer provides for you the peace of mind, in design reliability, and helps to ease your permit application through the structural review process.

Engineered Buildings Part I

Some or all of a building collapses in a wind or snow storm. Upon examination, it is determined the building had several major weaknesses due to lacking engineering. The building owner is frustrated and angry as he truly believed he had purchased a properly engineered building.

A properly engineered building, in the average client’s mind, is what I refer to as a fully engineered building. A fully engineered building is developed by following three structural design steps:

  1. Calculate all loads and load combinations to which the building will be subjected.
  2. Determine how loads are distributed to building elements (this step is known as structural analysis).
  3. Then select components and connections capable of handling forces to which they will be subjected. In practice, selected components and connections will directly influence structural analysis.

A fully engineered building is one in which all structural component interactions are properly accounted for during structural analyses, and forces resulting from these analyses are used to size all components. Non-engineered building design processes do not account for component loads or actual component strengths. In the middle lies a partially engineered building.

In snow country, many collapsed building failures are triggered by unbalanced snow loads (drift or sliding snow loads) which structures should easily withstand. Upon forensic failure review, it becomes obvious these buildings were not fully engineered.

This engineering lack can be attributed to many companies involved in low or moderate risk building construction does not employ engineers.  Nor do they hire an engineer to perform structural engineering calculations for buildings they construct. Each year this lack of responsible building designing results in numerous buildings constructed which contain multiple components and/or connections not sized to handle loads the building is expected to experience.

Companies which erect or provide non-engineered buildings generally try to copy designs they have seen elsewhere. This causes a myriad of problems.

Simply copying, altering and/or scaling up an existing design completely ignores the fact loads like wind and snow are highly dependent on size, shape, orientation and building location. Also local topography characteristics and size, shape and orientation of attached and surrounding structures influence design. Additionally, snow, wind and other structural loads act in a variety of combinations and a building must be designed to handle all load combinations to which it could be subjected. Total ignorance of applicable loads and load combinations is a non-engineered building design hallmark and explains why so many buildings are damaged by wind and unbalanced snow loads which would not damage a fully engineered building.

Extremely weak connections between components are prevalent in non-engineered structures. Stresses which surround bolts, screws and nails are complex and control fastener size, spacing and placement relative to component ends and edges they connect. These conditions are seldom realized by builders attempting to mimic other building designs. Improperly assembled connections trigger and/or contribute to many building failures.

Some building companies are established by individuals who begin erecting buildings for companies which employ engineers and sell fully engineered packages. While I applaud anyone’s entrepreneurialism in starting their own business, it is indeed scary when some of these individuals start erecting or providing non-engineered buildings. Participating in engineered building erection does not make one an expert in building design, no more than designing a building makes one an expert in safe and efficient building construction.

Very few builders, architects, code officials and non-structural engineers understand the true complexity of a fully engineered pole building system. Several building elements perform multiple functions not apparent or understood by those not actively engaged in post-frame building engineering. In addition to having no idea of  loads to which a component is subjected, builders are not familiar with all methods available to resist applied loads and do not have the expertise needed to determine proper size, support system and connection designs for a building component.

One of my pet peeves is builders who call me and argue with me over “how you should design your buildings” based on the 5 or 6 pole buildings they’ve put up over the past 10 years.  Just because they didn’t fall down (yet), is their claim to be the expert!  Sadly, clients too often are duped by these guys because: 1. “This is just the way we DO buildings here” and 2. “Joe has been building around here for 30 years so he must know”.  Again, just because “Joe’s” buildings haven’t yet fallen down (and maybe never will) does not guarantee longevity and more importantly not calculated safety factors.

When I owned Apex Roof Truss, we sold a set of 60′ trusses to a builder for a building up north. Only after the building collapsed due to a record snowfall, did we get to see photos of it prior to collapse. At the time, there were several feet of snow on the roof, and the purlins between the trusses were sagging a good three inches between the trusses. Now the builder (who had written us a bum check for the trusses and his contractor registration had expired) built the building “the way he always did”. Two problems.  One, he used 2×6 purlins on edge, where the truss spacing and snow load would have taken 2×8 to carry the load (hence the hug sag) and two, he left out most of the required truss bracing.

When the purlins started breaking, everything else started sucking in behind them.

Come back tomorrow for Part 2 of 3 in my rant on under designed buildings – meaning NON –engineered pole buildings.