Tag Archives: Vult wind speed

Building Department Checklist Part I

BUILDING DEPARTMENT CHECKLIST 2020 PART I

I Can Build, I Can Build!

Whoa there Nellie…..before getting all carried away, there are 14 essential questions to have on your Building Department Checklist, in order to ensure structural portions of your new building process goes off without a hitch.  I will cover the first seven today, finishing up tomorrow, so you have a chance to take notes, start your own home file folder of “what to do before I build”.  Careful preparation will be key to having a successful building outcome (whether post frame or some other structural building system).

Provide answers to these questions to your potential building providers!

IMPORTANT SIDE NOTE: Building Departments’ required snow and wind loads are absolute minimums in an attempt to prevent loss of life during extreme events. They are not established to prevent your building from being destroyed. Consider asking your providers for added investment required to increase wind and/or snow loads beyond these minimums.

#1 What are required setbacks from streets, property lines, existing structures, septic systems, etc.?

Seemingly every jurisdiction has its own set of rules when it comes to setbacks. Want to build closer to a property line or existing structure than distance given? Ask about firewalls. If your building includes a firewall, you can often build closer to a property line. Creating an unusable space between your new building and a property line isn’t very practical. Being able to minimize this space could easily offset a small firewall investment. As far as my experience, you cannot dump weather (rain or snow) off a roof onto any neighbor’s lot, or into an alleyway – so keep those factors in mind.

#2 What Building Code will be applicable to this building?

Code is Code, right? Except when it has a “residential” and also has a “building” version and they do not entirely agree with each other.

Also, every three years Building Codes get a rewrite. One might not think there should be many changes. Surprise! With new research even things seemingly as simple as how snow loads are applied to roofs…changes. Obviously important to know what Code version (e.g. 2012, 2015, 2018, 2021) will be used.

 

#3 If building will be in snow country, what is GROUND snow load (abbreviated as Pg)?

Make sure you are clear in asking this question specific to “ground”. When you get to #4, you will see why.  Too many times we’ve had clients who asked their building official what their “snow load” will be, and B.O. (Building Official) replied using whichever value they are used to quoting.  Lost in communication was being specific about “ground” or “roof” snow load.

As well, what snow exposure factor (Ce) applies where a building will be located? Put simply, will the roof be fully exposed to wind from all directions, partially exposed to wind, or sheltered by being located tight in among conifer trees qualifying as obstructions? Right now will be a good time to stand at your proposed building site and take pictures in all four directions, and then getting your B.O. to give their determination of snow exposure factor, based upon these photos.

#4 What is Flat Roof Snow Load (Pf)?

Since 2000, Building Codes are written with flat roof snow load being calculated from ground snow load. Design snow load has become quite a science, taking into account a myriad of variables to arrive with a specific roof load for any given set of circumstances.

Unfortunately, some Building Departments have yet to come to grips with this, so they mandate use of a specified flat roof snow load, ignoring laws of physics.

Make certain to clearly understand information provided by your Building Department in regards to snow loads. Failure to do so could result in an expensive lesson.

#5 What is “Ultimate Design” or Vult wind speed in miles per hour?

Lowest possible Vult wind speed (100 miles per hour) only applies in three possible states – California, Oregon and Washington for Risk Category I structures. Everywhere else has a minimum of 105 mph.  Highest United States requirement of 200 mph for Risk Category III and IV buildings comes along portions of Florida’s coastline (although there are scattered areas nationally defined as “Special Wind Regions).  Don’t assume a friend of yours who lives in your same city has your same wind speed.  City of Tacoma, WA has six different wind speeds within city limits!

Vult and nominal design wind speed (Vasd) are different and an errant choice could result in significant under design (or failure). Make certain to always get Vult values.

#6 What is wind exposure (B, C or D)?

Please Take a few minutes to understand their differences:

(https://www.hansenpolebuildings.com/2012/03/wind-exposure-confusion/).

A Building Department can add hundreds, or even thousands, of dollars to your project cost, by trying to mandate an excessive wind exposure.  Once again, a good place for photographs in all four directions from your building site being shared with your Building Department.  Some jurisdictions “assume” worst case scenarios.  Meaning, your property could very well have all four sides protected and easily “fit” category B wind exposure requirements.  However, your jurisdiction may have their own requirement for every site in their jurisdiction to be wind exposure C, no matter what.  It’s their call.

#7 Are “wind rated” overhead doors required?

Usually this requirements enforcement occurs in hurricane regions. My personal opinion – if buying an overhead door, invest a few extra dollars to get one rated for design wind speeds where your building will be constructed. Truly a “better safe, than sorry” type situation.

I’ve covered seven most important questions for your Building Department Checklist, and they really weren’t so difficult, were they?  Come back tomorrow to find out the last seven!

Moving Pole Barns

Moving a Pole Barn
Most of us American adults have, at some time in our lives, visited a county or state fair. Adjunct to these events is the inevitable midway – where carnies (those wonderful and frequently interesting folks) hock their wares and try to interest one and all in a game of chance. Amongst these games is typically one where a rifle of some sorts spews water, air or corks at moving targets allowing the joyous winner to recoup his or her investment into a wonderous prize which is usually worth far less than the price of admission to the game.

Well, I hate to break the news, but the chances of coming out ahead at the midway are better than the chances of coming out ahead on moving a pole barn (aka post frame building).

Reader GEOFF in SNOHOMISH writes:
“I have a pole barn that I want to move. I had plans drawn by an engineer to erect it after I moved it. (required by the county) he looked at the original building, but drew the plans with a full footing and foundation. When I told him that this is a pole building and all the weight is carried on the posts he didn’t get it. Does a pole barn have to have footing and a foundation?”

Mike the Pole Barn Guru responds:
Well Geoff, there are issues going on here much larger than just your question, which I will address first.

Post frame buildings typically have a footing (most usually a concrete pad poured at the bottom of an augured hole) and the foundation is the pressure preservative treated wood column which is typically all or partially encased in concrete. There is most generally no structural reason to have a continuous concrete footing and foundation wall, such as one might see supporting a stick framed building.

I would encourage your engineer to make a modest financial investment into the NFBA (National Frame Building Association) Post-Frame Building Design Manual (read more about it here: https://www.hansenpolebuildings.com/2015/03/post-frame-building-3/).

Now the big picture:
You were lucky to have found a registered professional engineer who was willing to put his career on the line to seal plans for a post frame building which has been taken apart and moved, unless he placed some extreme caveats as to potential damaged materials. Besides this, chances are good the building in question was not built to the current Building Code requirements, and some significant modifications would need to be made in order to upgrade it to currently accepted standards.

The biggest changes involve wind design – where buildings are now required to be designed using Vult for wind speeds, rather than the lower Vasd values. The trusses, if undamaged, should be checked for structural adequacy using the most recent Code.

You have already made some financial investments, you might as well help to educate your engineer, as well as get your moving building up to the modern version of the Code.