Tag Archives: Risk Category I

Roof Collapses Due to Heavy Snow are Largely Avoidable

Roof Collapses Due To Heavy Snow Are Largely Avoidable.

Portions of this article are thanks to a February 25, 2019 article by Bill Steffan at www.woodtv.com

 

 

 

 

 

 

 

“Above pic. is the Negaunee Schools bus garage in Marquette Co., Michigan.  The roof collapsed under the weight of heavy snow over the weekend.  There were 16 buses inside the garage when the collapse occurred.  The collapsed triggered the sprinkler system and that led to a substantial accumulation of ice.  This was one of several buildings that had a roof collapse due to heavy snow in Marquette Co. 

Another collapse occurred at Shunk Furniture.  The force of the collapse blew out windows in the building.  “The first buildings to be concerned about are the pole buildings, the large-span pole buildings with truss spacings of eight foot or greater,” said Gary Niemela, Owner of Skandia Truss.”Those are usually the ones to be concerned about. Probably want to take the heavy snowload off. If the snowload is three to four feet deep on those, you’re going to want to do something,” said Niemela.”

I am going to address several issues, all of them ones leading to a better investment of a new post frame building owner’s dollars.

What, a Building permit?

In a surprising number of jurisdictions across our country, post frame (pole barn) buildings are exempted from a building permit process for one of several reasons. In some areas, there are just no actual building departments. Next step up is a “Building Permit” is issued for a minimal fee (usually in a clerk’s office) usually to get it added to property tax reevaluations.

In my humble opinion every building should have RDP (Registered Design Professional – architect or engineer) sealed plans submitted to an authority who can do minimally invasive site inspections via one of a myriad of online live chat options. Permits and payments could be obtained electronically. This type of system could even be contracted out to third-party providers on a percentage type contract with carefully worded expectations so there is not someone having hurt feelings at a later date.

But I Have to Pay for a RDP!

Yes you do and a good one will save you more money than they cost (or give you a greater value) in efficient use of materials and ease of construction. Favorite articles is on this very subject: https://www.hansenpolebuildings.com/2018/08/minimum-design-loads-and-risk/.

Do Away With Risk Category I

I can hear people screaming now about how much more they are going to have to pay to get a building designed for a once in 50 year occurrence (Risk Category II) rather than once every 25 years. For practical purposes, you cut in half risks to life and property from a catastrophic failure. In many buildings added investment will be minimal, as compared to gain in reliability.

Insurance Company Discounts

Property insurers should offer some discounts for building from RDP sealed plans, as well as a further discount for buildings designed for above Code minimum climactic loads.

Minimum Design Loads and Risk

Minimum Design Loads and Risk

Model Building Codes, such as IBC (International Building Code), offer minimum design loads for climactic forces such as snow and wind. As building permit issuing agencies adopt codes, within their scope they can establish minimum values for their particular jurisdiction.

Key word here “minimum” – least values a building may be designed for and still obtain a permit to build.

I have long been an advocate for structural designs above minimum requirements. All too often potential new post frame building owners have not had adequate consultative design recommendations enough to find out increases in structural strength are often achieved with minimal investment.

For an earlier article concerning this subject please see https://www.hansenpolebuildings.com/2015/11/bike-helmets-and-minimum-building-design-loads/.

From IBC Section 1604.5, “Each building and structure shall be assigned a risk category in accordance with Table 1604.5. Where a referenced standard specifies an occupancy category, the risk category shall not be taken as lower than the occupancy category specified therein.”

Balance of IBC Chapter 16, including Table 1604.5 may be perused here: https://codes.iccsafe.org/public/document/IBC2018/chapter-16-structural-design.

Buildings representing a low hazard to human life in event of a failure include agricultural facilities. In most jurisdictions, detached garages and shops are also considered to be a fit and these would be considered as Risk Category I. In many areas agricultural buildings are either permit exempt, or do not have to go through structural plan reviews and inspections.  Read a very expensive story about an agricultural building using minimal requirements: https://www.sbcmag.info/content/9/design-load-reductions-risk.

Risk Category I buildings are designed to allow for an occurrence greater than minimum design loads of once in 25 years (or a 4% chance in any given year). In theory, all buildings in this category should collapse within 25 years of construction.

Sobering, isn’t it?

Shopping for a new post frame building and want yours to be last one standing when a storm of a century comes to visit? If so, I would hope whomever you are speaking with offers options of increasing Risk Category from I to II. And bumping up snow loads by 5, 10 or even more pounds per square foot and/or increasing design wind speed by a few more miles per hour.

If you are not offered these options – ask for them. I’d like to have your building be left standing!

Turn a Horse Barn into a Home?

Re-purposing buildings is a popular American past time, as evidenced by the proliferation of big box lumber stores across the country. Here is a story about a new owner of an existing Hansen Pole Buildings’ horse barn, who is contemplating it becoming a home.

Tim writes:

“Hello, I just purchased a property that has a Hansen Pole barn that is new on it and I am wanting to convert to home any ideas and /or plans , I have attached a photo of barn  center section is 48×28 x14 and the 2 side sections are 48x12x10”.

Drum roll please:

You emailed me because you know and trust I am the expert and will not lead you astray. Or, this was the email address you happened to find, either one of which is totally fine.

In order to give you definitive answers I would need to know who the original purchaser of the building was, so we can pull up the plans and specifications for it, if they are available.

In the meantime, I will hope to give you my best guess answers. The existing building is most probably designed under Risk Category I of the International Building Code (being as it is used as a horse barn) which is for buildings of low risk to injure someone in the event of a catastrophic event. These would be non-residential structures. A residence is a Risk Category II structure – which has more stringent requirements for wind, snow and seismic events.

The real issues are most likely to come in designing to gypsum wallboard (sheetrock aka drywall) the walls and ceiling.

On the walls, the deflection criteria for walls which support drywall is much greater than a wall with only steel on the exterior. This can affect the size(s) of the columns and they may have to be added onto in order to provide adequate stiffness. It is likely you will use bookshelf girts on the walls to create an insulation cavity. If so, and they are properly sized, they should be stiff enough to support drywall.

The trusses, rafters and roof purlins are not designed to support the weight of a ceiling. This will require an engineered truss repair, as well as probably upgrades to the rafters on each side (addition of more members). If you are planning on attaching sheetrock to the underside of the roof purlins, more purlins will need to be added to reduce deflection – and the only real way to insulate between the purlins on the sheds is to use closed cell spray foam, which is not an inexpensive proposition.

Ventilation is going to pose an issue (which is why the closed cell insulation is the solve for the sheds). In the main portion of the building, if a dead attic space is created, it must be ventilated. I cannot determine from your photo if the building has enclosed overhangs or not. If they are enclosed and the ridge is vented, you are in luck. If not, then gable vents are the alternative and would need to be added.

My best recommendation – leave the barn and design a post frame home which truly fits your needs and lifestyle, rather than trying to fit what you want inside a preexisting box which requires a boatload of work to upgrade.