Tag Archives: building risk category

Building Department Checklist 2019 Part II

BUILDING DEPARTMENT CHECKLIST 2019 PART II

Yesterday I covered seven of what I feel are 14 most important questions to ask your local building department.  This not only will smooth your way through permitting processes, but also  ensures a solid and safe building structure.

Let’s talk about these last seven….

#8 What is accepted Allowable Soil Bearing Capacity?

This will be a value in psf (pounds per square foot). If in doubt, err to side of caution. As a rough rule – easier soil to dig, weaker it will be in supporting a building. A new post frame building will only be as solid as it’s foundation, and it’s foundation will be only as strong as soil it rests upon.

Some jurisdictions (most noticeably in California and Colorado) will require a soils (geotechnical) engineer to provide an engineered soil report, spelling out actual tested soil strength.  Other states may have requirements as well, so be sure to ask ahead of time.

#9  Is an engineered soils test required?

If so, get it done ahead of time.  Don’t wait. It’s easy to do and there are plenty of soil (geotechnical) engineers for hire.

#10 What is your Seismic Category (such as A, B, C, D-1, D-2)?

While rarely do potential seismic forces dictate design of a post frame building, there are instances where they can.  A high seismic potential, with high flat roof snow load and low wind load will be one case. Other case will be when you are considering a multiple story structure.

#11 Are wet-stamped engineer signed and sealed structural plans required to acquire a permit?

Some Building Department Officials will say no to this, yet during plans review process they request structural engineering calculations to prove design, or (worse yet) they make wholesale changes to plans, based upon how they think a post frame should be constructed.

Engineer sealed pole barnMy recommendation – invest in engineered plans. It becomes an assurance a registered design professional has verified your building will meet Code mandated loading requirements. In some cases, insurance companies offer discounts for buildings designed by an engineer. It’s certainly worth asking your agent for one!

In some cases, Building Permits will be granted with only requiring engineer sealed truss drawings. We do not condone this practice, as it creates a false sense of security.

Are exterior finished (showing roofing and siding) elevations required with building plans? Will more than two sets of drawings be needed for permit submittal?

#12 Verify Building Risk Category.

Most buildings not frequently occupied by public (not a home, business or municipal building) represent a low hazard to human life in event of a failure and are ASCE (American Society of Civil Engineers) Category I. This information can be found by Building Officials in IBC Table 1604.5 (not to be confused with Use and Occupancy classifications from IBC Chapter 3).

#13 In areas with cold winters, is frost depth greater than 40”?

All building columns or foundations must extend below frost line to prevent heave. We don’t design for any depth less than 40”, and have designed for up to seven feet deep in some areas!

#14 Does the Building Department have any unusual Building Code interpretations, amendments or prescriptive requirements for non-engineered buildings which could affect this building?

If so, get a copy from your building department for us, or anyone else whom might be considered to be a provider for your building project.

Even though “the Code is The Code”, there are a plethora of local folks who think they have better ways or better ideas than world’s smartest structural minds, who have actually written the Code. And once again, I can’t stress enough: build only from plans sealed by a Registered Design Professional (architect or engineer). It will make life easier all around when it comes to getting your permit, even if you have been told seals are “not required”.

No one inside or outside of a permit office wants a construction process to be any more difficult or challenging than necessary.  Being armed with correct information (after doing homework of course) will be a solid step in the right direction.

 

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!

How Long Will a Pole Barn Last?

This was a question asked of Hansen Pole Buildings’ Managing Partner Eric Graff, by one of our Building Designers, Elijah.

To begin with, let’s examine the 2012 International Building Code requirements for the Risk Category of the building.

1604.5 Risk category. 
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. 

garage-08-0224Most post frame buildings are Risk Category I, as they pose little threat to human life in the event of a failure. These buildings are designed so as the minimum Code Requirements for loading have a probability of being exceeded once in 25 years (a 4% annual probability).

Risk Category II would encompass most homes and commercial buildings with a probability of minimum loadings being exceeded once in 50 years (a 2% annual probability).

Risk Category III and IV are buildings with higher occupancy loads, are defined as essential facilities or ones which would create a greater hazard to human life in the event of a failure. These are designed to a once in 100 year occurrence or a 1% annual probability.

Post frame buildings can fall into any of these categories, so therefore should have basic structural designs and requirements (other than differentiation of applied loads) which are the same for any category.

The perceived ‘weak link’ in post frame construction would be pressure preservative treated columns embedded into the ground. The Code has specific requirements for treated wood (https://www.hansenpolebuildings.com/2012/10/pressure-treated-posts-2/), which (when followed) should provide for a structural system which will be good for a minimum of 100 years, as it would need to make the Risk Category III and IV requirements.

This does NOT mean there will be no maintenance needed to insure a lengthy lifespan.

Roofing and siding products (especially those which are not factory pre-painted steel over galvalume or galvanization) have fairly limited lifespans and will need to be replaced, resurfaced or repainted on a regular basis.

Given the current technologies available for steel roofing and siding paint systems, it is very possible the products which are installed today will yet be serviceable 100 years from now. Granted there is probably a high degree of color fade as well as some probability of rust.

When I inherited my home outside of Spokane, Washington in 1990, the existing cedar post frame garage was still serviceable after more than 50 years of regular use – yes, the untreated columns were showing some signs of decay, but otherwise if we would have owned the two Model A Fords the garage was designed for, it still would have been a nice two car garage.

The definitive answer to Elijah’s question – in all probability any given pole barn building will outlive its intended useful purpose.