Tag Archives: International Building Code

Building Department Checklist 2019 Part 1

BUILDING DEPARTMENT CHECKLIST 2019 PART I

I Can Build, I Can Build!

(First published six years ago, it was more than past time to update to reflect current code requirements!)

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 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 post frame building outcome.

#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 the small investment of a firewall. 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. IBC (International Building Code) only applies to post frame buildings, not IRC (International Residential Code:

(https://www.hansenpolebuildings.com/2018/10/what-building-code-applies-to-post-frame-construction/).

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 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 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. Now 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.  Don’t assume a friend of yours who lives in your same city has your same wind speed.  The city of Tacoma, WA has six different wind speeds within city limits!

Vult and nominal design wind speed Vasd are NOT the same thing. Make certain to always get Vult values.

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

Take a few minutes to understand the 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 the 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!

 

Plywood Siding Z-Flashing

Plywood Siding Z-Flashing

My first full time construction job was as an MEI (Momb Enterprises, Inc.) slave working for my framing contractor father and his brothers. 1970’s found T1-11 plywood siding to be very popular (as were disco balls) and we installed plenty of it. Where walls were higher than available panels of T1-11, one panel would be installed above another, between each was a thin Z shaped piece of galvanized steel flashing, known appropriately as Z-flashing.

Today’s writing has been spurred by reader GRIFFIN in LONGMONT who writes:

“Is there flashing between the horizontal joints of each T1-11 siding panel?  The inspectors are advising it’s required.”

Mike the Pole Barn Guru responds:

Because I so enjoy terminology such as “inspector said” I used internet power and Google to find a Building Code reference. Closest thing I could find would be this:

From 2015 IBC (International Building Code):

1405.4 Flashing.

Flashing shall be installed in such a manner so as to prevent moisture from entering the wall or to redirect that moisture to the exterior.”

Now common sense would tell me this joint would need to have some sort of flashing to prevent water infiltration in any case. And yes, Hansen Pole Buildings does include Z-flashing where needed for horizontal joints in plywood sidings.

There exists a technique for proper installation:

Galvanized Z-flashing, so-called because of its Z-shaped profile, keeps water from getting through horizontal joints between sheets of plywood siding. You set flashing upon top edge of each piece of plywood over a fat bead of caulk and hold it in place with just heads of roofing nails driven into sheathing. Don’t nail through flashing itself or it will eventually leak. Overlap ends of flashing by two or more inches and run a bead of caulk between them. And just before upper plywood panel becomes placed, caulk along top edge of metal as extra protection against water.

While I personally recommend using roll formed steel siding due to its longevity and cost effectiveness, some folks feel plywood siding will be their ideal design solution. For those, we provide proper and appropriate Z-flashing.

 

Whiskey Tango Foxtrot! Is It Ventilation?

Whiskey Tango Foxtrot! Is it Ventilation?

I really enjoy good food. In order to continue doing so and avoid weighing significantly more than I should, I do a treadmill run nearly every morning. To keep from expiring from utter boredom of exercise, I have wall mounted my flat screen LED television within easy viewing distance. With subscriptions to Amazon Prime and Netflix, I have yet to run out of movies and series to view. Most movie selections are either fairly old, or were box office challenged. One of these movies was 2016’s Tina Fay starring in Whiskey Tango Foxtrot, with a budget of $35 million and a box office take of $18.3 million.

Well, this article isn’t about how Tina Fey carried this movie. To be precise, it’s a movie title conveying my expression upon doing some recent reading.

Back in 2016 I had penned an article (https://www.hansenpolebuildings.com/2015/06/overhang/) mentioning a specific pole building company by name. A representative of this company recently contacted Hansen Pole Buildings’ owner Eric to let him know they did not appreciate being named. I was even kind enough to have included a live link to their website in my article, providing them with free press.

While editing, I happened to peruse their website. When a Whiskey Tango Foxtrot moment hit me…..

Under ‘Building Features’ I found this gem, “(Our standard roof to eave or gable design creates a fully ventilated structure making boxed overhangs an option, not a necessity)”.

I had to read it several times to fully get my head around what I thought I had read.

In order for this statement to be true, roof steel high ribs would need to remain unobstructed – allowing a free flow of intake air. This could possibly pose a challenge if one desires to keep small flying critters from entering a dead attic space.

In my humble opinion, this attempted ventilation intake ranges from laughable to totally ridiculous. However, I have found, nearly anything can be spun to sound like a benefit. What should be happening between roof steel and eave strut – placement of an Inside Closure (https://www.hansenpolebuildings.com/2015/12/the-lowly-inside-closure/), to seal these openings.

IBC (International Building Code) 2015 Edition tends to agree with me.

“1203.2.1 Openings into attic.

Exterior openings into the attic space of any building intended for human occupancy shall be protected to prevent the entry of birds, squirrels, rodents, snakes and other similar creatures. Openings for ventilation having a least dimension of not less than 1/16 inch and not more than ¼ inch shall be permitted. Openings for ventilation having a least dimension larger than ¼ inch shall be provided with corrosion-resistant wire cloth screening, hardware cloth, perforated vinyl or similar material width openings having a least dimension of not less than 1/16 inch and not more than ¼ inch.”

Thinking about a post frame building other than from Hansen Pole Buildings? Before possibly throwing away your hard earned cash, give us a call – if we feel someone else’s building has a better value than ours, we will be first ones to tell you to invest in it.

 

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!

Vinyl Gable Vents for Pole Barns

Vinyl Gable Vents for Pole Barns

Attic venting for post frame (pole barn) buildings is a challenge which can be resolved by the use of vinyl gable vents.

Reader KEN in BERRYTON writes:

“I have a pole barn with the ribbed siding, 3/4″ high ribs at 9″ spacing, with two smaller ribs in-between at 3″ spacing.  I need to add end wall gable vents (because I failed to have it built with eaves) because I want to install insulation in the ceiling and walls.  In reading your web information on gable vents, it seems that the vents you offer fit over the ribs as opposed to what I might find at my local Home Depot.  Can you clarify whether the vent you provide fits over the ribs so that I can get a weather tight seal.  If not indexed for the ribs, I am at a loss to understand how you can seal the vent against the ribbed siding.  Any guidance you could share would be very much appreciated.

I also read in a Q/A that dividing the square footage by 300 gives you the number of square inches of vent required.  My building is 60×30 which gives 1800 square feet divided by 300 would be 6 square inches.  I wonder if this is a misprint, that it should be 6 square feet.” 

Mike the Pole Barn Guru responds:

The Hansen Pole Buildings vinyl gable vents are designed with a “snap ring” which goes on top of the high ribs of the steel. To install, remove the snap ring and use the inside edge of it as a template to draw the location of the vent on the siding. Remember to cut just outside of the line, so the vent can be pushed through from the inside. Once it is pushed through, snap on the snap ring and you have a sealed vent! Just this easy and requires no extra framing.

And it is square feet, not inches. In your case you would need to have at least three square feet of net free area venting on each endwall, and it would need to be located in the upper half of the dead attic space. Just as an example an 18″ x 24″ rectangular vent will typically provide about 140 square inches of net free area.

The 2012 IBC (International Building Code) ventilation requirements may be accessed here: https://codes.iccsafe.org/public/document/IBC2015/chapter-12-interior-environment please see 1203.2.

 

Use and Occupancy Challenge Part II

See yesterday’s blog for Part I. To continue the discussion on Use and Occupancy:
Momentarily skipping a few chapters and going to Chapter 6 (because it would be too simple if the IBC was in order) the code book outlines different types of construction. Post frame buildings can fall under the following construction types:
The Type of Construction for post frame buildings is typically Type V.
602.5 Type V.
Type V construction is that type of construction in which the structural elements, exterior walls and interior walls are of any materials permitted by this code.

Table 601 gives TYPE V-B systems no fire rating (most typical for post frame construction). With a one-hour fire rating for the primary structural frame, bearing walls, as well as floor and roof construction and associated secondary members, post frame buildings could be classified as

TYPE V-A.
In some cases, a post frame building could also be Type III.

602.3 Type III.
Type III construction is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of any material permitted by this code. Fire-retardant-treated wood framing complying with Section 2303.2 shall be permitted within exterior wall assemblies of a 2-hour rating or less.

Now head back to Chapter 5.
504.1 General.
The height, in feet, and the number of stories of a building shall be determined based on the type of construction, occupancy classification and whether there is an automatic sprinkler system installed throughout the building.

504.2 Mixed occupancy.
In a building containing mixed occupancies in accordance with Section 508, no individual occupancy shall exceed the height and number of story limits specified in this section for the applicable occupancies.
504.3 Height in feet.
The maximum height, in feet, of a building shall not exceed the limits specified in Table 504.3.

In TABLE 504.3 we find the proposed building to be well under the wall height limitations for Type V-B buildings of 40’ without sprinklers or 60’ with.
504.4 Number of Stories.
The maximum number of stories of a building shall not exceed the limits specified in Table 504.4.

In TABLE 504.4 we find A-3 and U to be limited to one story without sprinklers, or two stories with sprinklers. Buildings with an R-3 category (residence) is three stories without or four stories with sprinklers.

Might the partial second floor be a mezzanine?
“505.2 Mezzanines.
A mezzanine or mezzanines in compliance with Section 505.2 shall be considered a portion of the story below. Such mezzanines shall not contribute to either the building area or number of stories as regulated by Section 503.1. The area of a mezzanine shall be included in determining the fire area. The clear height above and below the mezzanine floor construction shall not be less than seven feet.
505.2.1 Area limitation.
The aggregate area of a mezzanine or mezzanines within a room shall not be greater than one-third of the floor area of that room or space in which they are located. The enclosed portion of a room shall not be included in a determination of the floor area of the room in which the mezzanine is located. In determining the allowable mezzanine area, the area of the mezzanine shall not be included in the floor area of the room.”
If the second floor was 37 feet or less in length it might possibly become a mezzanine, which could alleviate some of the fire separation issues. This is provided the area below is not divided up into individual spaces.

However….
“505.2.3 Openness.
A mezzanine shall be open and unobstructed to the room in which such mezzanine is located except for walls not more than 42 inches in height, columns and posts.
Exceptions:
Mezzanines or portions thereof are not required to be open to the room in which the mezzanines are located, provided that the occupant load of the aggregate area of the enclosed space is not greater than 10.
2. A mezzanine having two or more exits or access to exits is not required to be open to the room in which the mezzanine is located.”
So, it does not appear the second floor will be able to be classified as being a mezzanine.

Come back tomorrow for Part III of a four part series.

International Residential Code and Tension Ties

International Residential Code and Tension Ties

Reader DENNIS in TRAVERSE CITY writes:

“ICC R602.10 is written to work with continuous foundations and vertical studs, not posts in holes and horizontal girts.
How does a person translate bracing into post-frame language?
An answer addressing tension ties would be helpful.”

From the 2015 International Residential Code (IRC):

R602.10 Wall bracing.

Buildings shall be braced in accordance with this section or, when applicable, Section R602.12. Where a building, or portion thereof, does not comply with one or more of the bracing requirements in this section, those portions shall be designed and constructed in accordance with Section R301.1.

R602.12 Simplified wall bracing.

Buildings meeting all of the conditions listed below shall be permitted to be braced in accordance with this section as an alternate to the requirements of Section R602.10. The entire building shall be braced in accordance with this section; the use of other bracing provisions of Section R602.10, except as specified herein, shall not be permitted.

  1. There shall not be more than three stories above the top of a concrete or masonry foundation or basement wall. Permanent wood foundations shall not be permitted.
  2. Floors shall not cantilever more than 24 inches beyond the foundation or bearing wall below.
  3. Wall height shall not be greater than 10 feet.
  4. The building shall have a roof eave-to-ridge height of 15 feet or less.
  5. Exterior walls shall have gypsum board with a minimum thickness of ½ inch installed on the interior side fastened in accordance with Table R702.3.5.
  6. The structure shall be located where the ultimate design wind speed is less than or equal to 130 mph and the exposure category is B or C.
  7. The structure shall be located in Seismic Design Category A, B or C for detached one- and two-family dwellings or Seismic Category A or B for townhouses.
  8. Cripple walls shall not be permitted in three-story buildings.

R301.1 Application.

Buildings and structures, and parts thereof, shall be constructed to safely support all loads, including dead loads, live loads, roof loads, flood loads, snow loads, wind loads and seismic loads as prescribed by this code. The construction of buildings and structures in accordance with the provisions of this code shall result in a system that provides a complete load path that meets the requirements for the transfer of loads from their point of origin through the load-resisting elements to the foundation. Buildings and structures constructed as prescribed by this code are deemed to comply with the requirements of this section.

Please keep in mind, the IRC is a prescriptive code – it calls out the approved methods to put a stick framed building together, within the prescribed load parameters. Post frame (pole) buildings are NOT covered by the IRC, other than:

R301.1.3 Engineered design.

Where a building of otherwise conventional construction contains structural elements exceeding the limits if Section R301 or otherwise not conforming to this code, these elements shall be designed in accordance with accepted engineering practice. The extent of such design need only demonstrate compliance of nonconventional elements with other applicable provisions and shall be compatible with the performance of the conventional framed system. Engineering design in accordance with the International Building Code is permitted for buildings and structures and parts thereof, included in the scope of this code.

Accepted engineering practice and in accordance with the International Building Code  would lead your RDP (Registered Design Professional – Architect or Engineer) to utilize the NFBA (National Frame Building Association) Post-Frame Building Design Manual Second Edition.

While it is possible a design utilizing tension ties could be done, it is probably far more practical to utilize the strength and stiffness of properly fastened steel panels to transfer shear loads from the roof through the endwalls to the ground.

A Wood Floor in a Garage

A loyal reader writes:

“Hi. Good morning! As I read your post about a wood floor in a work shop, it reminded me of my research into a garage with a wood floor. I have often wondered, can this be done?

So I ask you, can this be done?

I am not a rich man, nor do I have much money. I have to be frugal with everything I do and everything I do must be durable and last for a very long time, life hopefully. Hence I am pondering building the things I want in stages.

The size up front will be 16×40. Maybe 20×40 if it’s not much more expensive. Later on, another building attached in the same size dimension ending with a 32×40 or a 40×40.

I would not mind having space in the attic to do things with, but the space I gave you can be used wisely for that anyway.

I will also tell you that I am not what the world considers a young man with a lot of time left on the Earth. I first and foremost need that garage.

I look forward to your answer. I would even like to have a price quote. I live in a mobile home that I once was pondering turning into a house with a garage. But most articles tell me it is not a wise thing to do.

Thank you,
Steven

P.S.- I live in central Alabama. Have a wonderful day!”

Mike the Pole Barn Guru says:

Yes, a garage can be built and designed with a wood floor. Whether or not it should be done is the true question – as it is not going to be an inexpensive proposition.

At my home near Spokane, Washington, I have a post frame garage which is built on a steeply sloping hillside (14 feet of grade change across 24 feet of depth). While the under structure is wood, it does have a concrete slab poured on top of the framing. In hindsight, I would have used fire retardant treated plywood on top of the joists and then sealed the top surface of the plywood. I say this because the concrete slab, in my humble opinion, has not held up as well as I would have liked it to over the past 25 years (it has numerous cracks and sprawls).

The IBC (International Building Code) specifies a uniformly distributed live load of 40 pounds per square foot (psf) (which would be the same as non-sleeping areas of a residence) for garage floors along with the requirement of: “Floors in garages of buildings used for the storage of motor vehicles shall be designed for the uniformly distributed loads of the Table (UBC 1607.1) or the following concentrated loads: (1) for garages restricted to passenger vehicles accommodating not more than nine passengers, 3,000 pounds acting on an area of 4-1/2 inches by 4-1/2 inches.”

This 3,000 pound concentrated load, if it was based upon beams every 12 feet and joists every two feet would equate out to a uniform live load requirement of 125 psf.

Garage floor parking surfaces must be made from approved noncombustible and nonabsorbent materials. FRTW (fire retardant treated wood)might meet with the approval.

Engineered post frame buildings, for any use, are designed to last not only your lifetime, but many lifetimes to follow – so they are a great permanent investment. If the ability to get the most bang for your investment is important, my encouragement would be to borrow a small amount to enable you to get the entire building footprint you ultimately desire, rather than doing the building in two phases. It is always far more economical to do the project once, than in multiple phases and there will be savings both in materials as well as your time to assemble.

Design Wind Speed Changes

Design Wind Speed Changes with Building Code Editions

Every three years a new version of the International Building Code (IBC) is printed, which brings with it the latest and greatest information for building design as approved by Code Officials. State and local permit issuing jurisdictions then can either adopt or amend the Code as they best see fit.

Even though the Code is updated on a three year cycle, some jurisdictions opt to continue to utilize earlier versions of the Code.

Provisions for design loads are set forth in Chapter 16 of the IBC.

There are significant changes to the design wind load requirements for fenestration between the 2009 IBC and the 2012 editions of the same code. These are due to significant changes to the wind load provision of ASCE (American Society® of Civil Engineers) 7 between the 2005 and 2010 edition.

The design wind load provisions of the 2005 and earlier editions of ASCE 7 were based upon allowable stress design of building components. The intent of this method was to provide loads to which the building components had a fairly high likelihood of being exposed during the service life of the building. The building components were then designed to remain serviceable (i.e. not require replacement) when subjected to this load.

The 2010 edition of ASCE 7 provides design wind load provisions which are based upon strength design of building components. This method provides loads which have a lower likelihood of occurring during the service life of the building. The building components are then designed not to fail (rupture) when subjected to this load.

This change in methodology results in higher design wind speeds and pressures. At first glance, this might give the appearance of requiring higher DP (Design Pressure) ratings. In actuality, the 2012 IBC contains provisions to multiply this new, higher load by a factor of 0.6 for the purpose of conversion to the more traditional method of determining the design wind pressure based upon allowable stress design. It is very important the builder, code official, manufacturer and anyone else involved in choosing or approving the structural building design for a particular application understand the higher design wind pressure provided by the 2012 IBC must be multiplied by this 0.6 conversion factor.

In most, but not all, cases this conversion results in required design pressure ratings which are roughly comparable to the more traditionally determined values.

ASCE7-10 also provides three different design wind speed maps. The different maps are based upon the assigned Risk Category of the building being designed.

  1. There is one map for buildings whose collapse would present a low risk to human life, such as barns and storage facilities.
  2. There is a second map for buildings whose collapse is considered to be a moderate hazard to human life. Most buildings fall within this category.
  3. There is a third map for buildings whose collapse is considered a high threat to human life, and for those which are considered essential facilities. The former includes assembly or education buildings designed to house groups of 250 or more people, some medical care facilities and any other buildings designed to house 5,000 people or more. Essential facilities include occupancies such as hospitals and police and fire stations, which are essential during emergency response situations.

The new maps result in higher design wind loads for buildings of moderate hazard to human life than for those of lower hazard. The highest design wind loads are given by the third map for buildings of high hazard to human life and essential facilities. Previous editions of ASCE 7 and the IBC also required these types of buildings to be designed to higher design loads, but the actual increase was applied in a different manner.

Considering a new post frame (pole) building? If you are looking at a building which is NOT designed by a registered design professional (RDP – engineer or architect) then there is an excellent chance the person or persons involved in the design do not understand the changes brought about by the newer editions of the Code and you could end up with an under designed building.

Under design can result in catastrophic failure – or even death. Don’t take the risk, demand an engineered building.

Your life or the lives of your loved ones could be at stake.

Sloping Concrete Floors

Another great and well thought out question, which is best answered at length.

Customizable Workshop for Large HobbiesDear Pole Barn Guru: The construction manual states that concrete slab floors should be poured so there is 3-3/4” of skirt board left exposed above the slab. What do you do if you want or need to have a typical slab slope toward the front of the building? On my 36’ garage that might be around a 4.5” change in slab height from back to front. Since I’m using sheetrock inside (not steel) my thought is that I really only need to have the recommended slab height around my doors at the front of the building to avoid problems and the slab could be poured higher in the back. Appreciate the input! DAN in EVERGREEN

DEAR DAN: The IBC (International Building Code) vaguely addresses this issue: where the minimum per IBC Section 406.1.3 is stated as, “….The area of floor used for parking of automobiles or other vehicles shall be sloped to facilitate the movement of liquids to a drain or toward the main vehicle entry doorway….”.
The command has been given. However the Code does not specifically give an amount of slope. The general consensus is the minimum slope should be 1/8” per foot. This would work out to exactly the 4.5 inches in 36 feet which you had guesstimated.
The important part is to have the top of the slab at door openings be at the 3-3/4” of exposed skirt board left. I’ve come up with different solutions in different buildings of my own. In my oldest, small 22 x 24 garage, the floor is all sloped from front to back. In my two most recent buildings, central floor drains were installed and the floors slope to the drains.

floor-drainI have found I truly like having the floor drains. This allows the floor around the perimeter to all be poured to the same level, which aids in being able to apply inside finishes (such as gypsum wallboard) without the need to custom cut every piece – so it is easier to construct. This also minimizes the overall slope amount, as your 36’ floor could drop the 1/8” per foot in 18 feet for 2-1/4”. By excavating down, instead of having to build up, the amount of compacted fill is reduced (again saving money).
I also happen to live where it is below freezing for more months than I like to think about. By having a central floor drain, I can wash my vehicles in my nice heated spaces and have the wash water go down the drain, as opposed to forming an ice dam in front of my doors.

16 Foot Eave Height and Lofts

We get a few requests for quotes from clients every day – actually more like a few hundred. With this volume of inquiries, it goes to figure we see and hear a broad variety of ideas.

Buildings with loftsOne of the more popular ones is clients who want a 16 foot tall eave height and a loft (either a full or partial second floor).

When I do training sessions for our Building Designers, one of my cautions is folks are generally dimensionally challenged. This particular lofty situation being a case in point.

Most frequently eight foot high ceilings are considered a standard, and allow for two sheets of drywall to be stacked horizontally on a wall without the need to cut sheets lengthwise. The International Codes (IBC – International Building Code and IRC – International Residential Code) do allow for finished ceiling heights as low as 7’6” throughout buildings (as well as seven foot in bathrooms and kitchens), however the lower height increases the amount of work as well as waste.

So, two eight foot high ceilings add up to 16 feet, so a 16 foot eave should be ideal – right?

Wrong.

I’ve had some fun writing about eave height in the past, and you can too by checking out this previous article: https://www.hansenpolebuildings.com/2015/02/eave-height-2/

In our above 8 + 8 = 16 equation, there are a few things being left out. This includes:

A concrete floor – a nominal four inch thick slab on grade is going to chew up 3-1/2 inches when all is said and done;

The thickness of the roof system – as the eave height is measured to the bottom of the roofing, plan upon the loss of at least six inches of thickness to the trusses and roof purlins. If designing for a conditioned (heated and/or cooled) structure, plan upon trusses with “energy heels” https://www.hansenpolebuildings.com/2012/07/raised-heel-trusses/

These could be as deep as nearly two feet in order to allow for R-60 blown in insulation);

Oh, and last but not least, the thickness of the loft floor itself. Most folks who want loft floors would like to minimize the number of supporting columns, so planning upon the loss of a foot minimum. If the floor joists need to span much more than 20 feet (or loads greater than standard residential loads are applied), then engineered wood floor trusses come into play with a general rule of thumb being an inch of depth per foot of span.

From a practicality standpoint, the absolute minimum eave height to allow for two floors should be no less than 18’.

History of a National Design Standard

History of the Development of a National Standard of Practice for Wood Design

NDSFrom time-to-time you might see the term NDS® (National Design Specification® for Wood Construction appear in my blogs, and it is referenced on every set of Hansen Pole Buildings plans, as well as within the International Building Codes.

Me, being the curious sort, wanted to know the history of the NDS® and I was able to find it in the 1997 NDS® commentary. I felt it interesting enough to share:

In the early part of the century, structural design with wood was based on general engineering principles using working stresses or design values published in engineering handbooks and in local building codes. These design values were often not in agreement, even for the same species of wood. Further, on most cases, the assigned values were not related to lumbar grade or quality level.

To meet the growing need for a national standard of practice, the Forest Products Laboratory, an agency of the Forest Service, U.S. Department of Agriculture, prepared a guide for grading and determining working stresses for structural grades of timber.

It provided basic working stresses for clear, straight-grained material of the important commercial species and presented strength ratios for adjusting basic strength values for each species for the effect of any size and location of knots or other natural characteristics permitted in a structural grade. The basic stresses and the strength ratios established in Miscellaneous Publication 185 were based on extensive test data for small, clear specimens and structural timbers obtained from over twenty years of testing and evaluation at the Forest Products Laboratory.

In 1934, the National Lumber Manufacturers Association (now the American Forest & Paper Association assembled the information given in Miscellaneous Publication 185 and working stresses derived therefrom together with engineering equations and other technical information on wood in the publication “Wood Structural Design Data” (WSSD) Included as supplements to the publication was design information for timber fastening. A major component of the WSSD was extensive span and load tables for various sizes of timber beams and columns.

With the initiation of World War II, the need for a comprehensive national design standard for timber structures, including wood connections, became more urgent. The Technical Advisory Committee of the National Lumber Manufacturers Association undertook a more than three year effort to develop the necessary specification in close consultation with the Forest Products Laboratory. The result was The Specification for the Stress-Grade Lumber and It’s Fastening. The Specification included allowable unit stresses fort stress graded lumber, design formulas, and design loads and provisions for timber connector, bolted, lag screw, nail and wood screw joints. Also included were guidelines for the design of glue-laminated structural members.

Despite numerous revisions since 1944, the scope of the Specification has remained essentially unchanged.

To an increasing degree in recent years, the results of research conducted at universities and other private and public laboratories, in Canada and other countries as well as the U.S.have been utilized to improve the Specification as a national standard of practice for wood construction.

In 1992 NFPA (National Forest & Paper Association) was accredited as a canvass sponsor by the American National Standards Institute (ANSI). The Specification subsequently gained approval as an American National Standard with an approval date of October 16,1992.

And there you have it, years of testing and revisions to the Specification, which is the basis for the engineering which goes into every Hansen Pole building kit package.

For those who want or need to know more, visit this website which has the full story of the history of a National Standard of Practice for Wood Design:

https://www.awc.org/pdf/codesstandards/publications/nds/archives/Part00CoverAndHistorypp1to3.pdf

Cross Laminated Timber

And long-time reader Vincent Phelps has another great question: “CBS Sunday morning had a segment on CLT, Cross Laminated timber. It brought timber frame construction to mind. Your thoughts on this technique for the Pole builder?”

https://www.cbsnews.com/news/living-the-high-life/

Cross-laminated timber (CLT) is a large-scale, prefabricated, solid engineered wood panel. Lightweight yet very strong, with superior acoustic, fire, seismic, and thermal performance, CLT is also fast and easy to install, generating almost no waste onsite. CLT offers design flexibility and low environmental impacts. For these reasons, cross-laminated timber is proving to be a highly advantageous alternative to conventional materials like concrete, masonry, or steel, especially in multi-family and commercial construction.

CLT PanelA CLT panel consists of several layers of kiln-dried lumber boards stacked in alternating directions, bonded with structural adhesives, and pressed to form a solid, straight, rectangular panel. CLT panels consist of an odd number of layers (usually, three to seven,) and may be sanded or prefinished before shipping. While at the mill, CLT panels are cut to size, including door and window openings, with state-of-the art CNC (Computer Numerical Controlled) routers, capable of making complex cuts with high precision. Finished CLT panels are exceptionally stiff, strong, and stable, handling load transfer on all sides.

There are some CLT fallacies being circulated:

  • CLT isn’t in the Building Code – wrong, CLT panels have great potential for providing cost-effective building solutions for residential, commercial, and institutional buildings, as well as large industrial facilities in accordance with the International Building Code.  In 2015, CLT will be incorporated into the International Building Code (IBC). The IBC recently adopted ANSI CLT Standard PRG 320 into the 2015 IBC, so you can request a design review based on it now and submit it as an alternate material, design and methods (AMM).
  • It is wood, it burns – Like using a few 12-inch-diameter logs to start a camp fire, mass timber does not catch fire easily. In fact, CLT acts more like concrete. Mass timber is not conventional so it is very hard to light, and once it is lit, it wants to put itself out. A research project recently completed at FPInnovations showed CLT panels have the potential to provide excellent fire resistance, often comparable to typical heavy construction assemblies of non-combustible construction. CLT panels can maintain significant structural capacity for an extended duration of time when exposed to fire.
  • It takes a specialized crew – Keep in mind, CLT is just another form of glue laminated timber (glulam). It is just wood, so it designs and builds on the earlier technology. CLT panels, like other industry panels (precast concrete or SIP panels), provide easy handling during construction and a high level of prefabrication facilitation and rapid project completion.  A conventional wood installation crew with other panel experience can lift, set, and screw down CLT panels, and with a manufacturer provided installation plan, it goes even faster.
  • It isn’t environmentally friendly – CLT is manufactured 2×6 lumber from trees harvested from sustainable managed forests, and mostly Mountain Pine Beetle kill trees. If we don’t use them, they decay and emit carbon back into the atmosphere. Wood is also the only primary structural material which grows naturally and is renewable. In fact, according to “Sustainable Forestry in North America,” during the last 50 years less than 2% of the standing tree inventory in the U.S. was harvested each year, while net tree growth was three percent.
  • It is expensive – When considering the total in-place value of a CLT system, it is cost competitive to other plate building materials. But you also need to consider all the value added benefits.More savings can be found in the reduced installation cost, usually 50% cheaper than installing other plate materials.With an earlier project completion date, you are open for business sometimes months ahead of schedule.

    The building structure will weigh less than half the weight of other construction types, so the foundation costs less money.

  • Job site safety is dramatically increased due to the prefabricated CLT panels and usually the only power tools are pneumatic drills.

The intent of CLT is not to replace light-frame construction, but rather to offer a versatile, low-carbon, and cost-competitive wood-based solution which complements the existing light frame and heavy timber options while offering a suitable candidate for some applications which currently use concrete, masonry, and steel.

My take on your question Vincent – CLT is a pretty neat product, but just like SIPs,

https://www.hansenpolebuildings.com/2015/02/sips/

they are not a practical design solution for most post frame applications.

However, if you want to construct a wooden skyscraper, CLT might be just the thing!

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.

Proposed Building Code Change to Add to Construction Costs

During each 3-year-cycle of the International Building Code (IBC) and International Residential Code (IRC), there exists an opportunity to propose modifications and improve the codes to recognize new and innovative construction.  During the final two weeks in April, the code proposal hearings were held in Louisville, Kentucky where several hundred proposals were discussed and considered for inclusion in the code.

large-span-trusses-150x150While post-frame construction is typically used in agricultural applications which are often (and in my humble opinion sadly) considered exempt from code compliance, more and more post-frame construction is either residential housing (IRC) or commercial (IBC) in nature.  In these cases, changes which impact the code may have an effect on how post-frame buildings are constructed.

Eight proposals were identified by NFBA (National Frame Building Association) staff as having a potential impact on post-frame construction.  While the majority of these proposals were defeated, the following action should be noted:

S138-16: Submitted by the Structural Engineers Association, this proposal was approved and will require special inspection for wood trusses with a clear span of 60 feet or greater or an overall height of 60 inches or greater.  While the clear span is not a major issue, the 60 inch height may impact a number of projects creating new cost/scheduling issues.  This change is scheduled to be included in the 2018 IBC.

Having spent my entire adult life installing, designing, selling, building, delivering and purchasing wood trusses, it would seem ludicrous to require a special inspection for wood trusses with an overall height of 60 inches or greater. This would add an extra layer of inspection to nearly every building (not only post frame) project, with seemingly no apparent rationale other than the employment of a large number of people to perform these inspections (most likely the same structural engineers who made this proposal).

Trusses spanning 60 feet or more, are already required to have special inspections, under the IBC: https://www.hansenpolebuildings.com/2013/12/wide-span-trusses/.

What can you do? Contact your local Building Official today and ask them to vote to repeal this costly measure which does little or nothing to improve the safety of buildings.

Building Code & Pole Buildings

When Plans Examiners Try to Apply the “CODE” to Pole Buildings

Today’s example happens to come from the State of Michigan, however it could happen in any Building Permit issuing jurisdiction in the U.S.

What is most interesting to me about this particular example is, last November I was invited to be a presenter at a meeting of Building Officials representing pretty much the northern half of the non-UP (Upper Peninsula) portion of Michigan. The topic was how the Building Codes apply to post frame (pole building) construction, and it was determined as a resultant, the Building Code could not be applied directly.

Building DepartmentLet’s have some fun with plan reviews, shall we?

(plan reviewer comments in yellow, referenced Code in italics below)

Footing size indicated is too small, (minimum 28″ round x 12″ thick) for sidewalls, or provide load calculations for each column. R403.1 to MBC 1805.7

R403.1 General. 

All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, wood foundations, or other approved structural systems which shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill.

Following this section of the Code is a Table which gives footing requirements for conventional light-frame construction, 4-inch brick veneer over light frame or 8-inch hollow concrete masonry, or 8-inch solid or fully grouted masonry.

The Code reference does not address footings for isolated, widely spaced columns.

Carrier beam size indicated is too small, three – 2” x 12” carriers minimum, required to carry truss and roof load. Table R502.5 (1)

The Table referenced is for exterior bearing walls in stick frame construction, where the dead load weights of shingles, roof sheathing, and gypsum drywall must be accounted for. It also is based entirely upon ground snow loads, without factoring in the allowable adjustments for this particular building being heated, as well as having a slippery steel roof.

Footnote for most of my readers who are in parts of the country where trusses are attached directly to the columns – this particular pole building is designed with a single truss every four feet, sidewall columns every eight feet and a header (aka “carrier beam”) attached to the columns to support the trusses.

The Table is also based upon a uniform load, which would be applicable for instances where trusses were placed every two feet (ala stick frame construction). Instead the carrier beam, is supporting a concentrated load at the center and every other truss rests directly on top of a column. This effectively reduces the load being carried by the beam by 1/3!

Confused?

Think of the load applied from a truss at two foot centers as being X. In an eight foot area, there would be an X at two, four and six feet or 3X. A truss at four foot only would carry twice as much load as a truss at two feet, or 2X. 2X divided by 3X = 2/3.

Carrier beam nail fasteners are sized too small and additional fasteners are required. Alternate structural screws, lags or bolts may be used. Submit revised fastener design. R 602.2

In my humble opinion, the Plans Examiner meant to reference R 602.3 which lists fastener schedules in Tables. The Tables do not even begin to address the connections found between a “carrier beam” and a column. The Plans Examiner appears to have possibly neglected to note the design presented has the carriers notched into the faces of the bearing columns, resulting in only enough fasteners being required to resist the uplift loads.

Buildings with an eave height 10′ or greater will require knee bracing or a full length diagonal brace in each corner. R301.1.1 to MBC1609.0, 2303.2

R301.1 Design. 

Buildings and structures, and all parts thereof, shall be constructed to safely support all loads, including dead loads, live loads, roof loads, flood loads, snow loads, wind loads and seismic loads as prescribed by this code. The construction of buildings and structures shall result in a system that provides a complete load path capable of transferring all loads from their point of origin through the load-resisting elements to the foundation.

It appears the reviewer’s comments are some sort of a local interpretation of how to handle the requirements of R301.1

I do believe I have previously presented an overwhelming case as to why not to use knee braces: https://www.hansenpolebuildings.com/blog/2012/01/post-frame-construction-knee-braces/

But what about a diagonal brace?

The entire concept of a diagonal brace in a wall is to assume the siding (in this case steel panels), lacks the ability to carry the shear loads being applied to the building.

Having been personally involved in the testing of light gauge steel panels, I can attest to their ability to carry a significant amount of load. (Read more at: https://www.hansenpolebuildings.com/blog/2012/08/this-is-a-test-steel-strength/)

Going back to the assumption of the siding not being able to carry the load, the building being reviewed has 1841.8 pounds of shear force being transferred to each endwall. Keeping things simple, let’s look at what it takes to even attach the suggested braces.

Generously assuming each brace would carry ½ of the applied load, each end of each brace must be able to have a connection adequate to carry around 921 pounds of force. A three inch long 10d common nail (3” x 0.148” diameter) driven through a 1-1/2 inch thick member into another member (assuming the weakest commonly used framing species) will support roughly 128 pounds. It is going to take a lot of nails in a very small area to make the connection work.

To have made this entire process quick, easy and simple for all involved, and to keep the Building Permit issuing authority out of the potential liability problems for being possibly construed as becoming the engineer of record, would be to simply require all pole building plans to be submitted with the seal of a registered design professional (engineer or architect) as well as the supporting calculations.

Which is exactly what this particular client opted to do. Case closed.

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.

Why You Need to Verify Design Criteria

Why to Verify Design Criteria

For those of you who are dedicated long term readers, I thank you. I’ve preached this subject more than once – but the message hasn’t gotten through to everyone yet. I will attempt to avoid boring anyone.

There are over 7000 building permit issuing jurisdictions in the United States. A full time employee, calling each of them for their most current code and load information, would need to reach and get data from nearly four an hour – for an entire year, and then it would be time to start all over again!

Each time a Hansen Pole Building is quoted, the design version of the Building Code, as well as all climactic forces the building is designed to, are listed on the pole building quote. Every quote also includes (in bold):

“You must confirm all code/design criteria with your Building Department prior to placing your order. 

We recommend taking this page to your building department for them to verify all design criteria listed above.”

Now my Dad used to tell me, “You can lead a horse to water, and if you hold its head under long enough, it will drown”.

Such may be the case with design criteria. Many clients not only follow instructions, they have done their homework in advance! They have contacted their Building Departments for information, before they even started pole building shopping.

We love these people! They are prepared.

Most of the rest, follow instructions well – they happily contact their Building Department and verify the information before ordering. We love you as well!

Then there are the very small percentage who make assumptions….well, we know where assumptions lead to.

When a post frame building kit package is ordered, one of the items Purchaser agrees to is:

“Seller’s designs rely solely upon occupancy category and structural criteria for and at specified job site address only, which have been provided and/or verified by Purchaser. It is Purchaser’s and only Purchaser’s responsibility to ascertain the design loads utilized in this Agreement meet or exceed the actual dead loads imposed on the structure and the live loads imposed by the local building code or historical climactic records. Purchaser understands Seller and/or Seller’s engineer(s) or agents will NOT be contacting anyone to confirm.”

design criteriaA real life example occurred recently. Client ordered a building kit and thought the roof snow load was to be 35 psf (pounds per square foot). Way too late into the game (prefabricated roof trusses had been delivered to the jobsite) the Building Department tells the permit applicant, “Oops”!

With the right information verified in the beginning, the cost difference would have been minimal. Many times, truss repairs to add five psf of load are fairly affordable. Not in this case – many of the wood members, as well as the majority of the roof truss metal connector plates were originally close to being fully stressed in the original design. For practical purposes, another truss needed to be added to every truss set, in order to meet the slightly higher loads.

Here is a case where ten minutes of the customer’s time to verify, would have saved well over a thousand dollars!

Plan ahead with your design criteria using our helpful Pole Barn Planning Guide.

Building Valuation Data

Every six months the International Code Council (ICC) provides updated Building Valuation Data (BVD) to its members. The BVD table provides the “average” construction costs per square foot, which can be used in determining permit fees for a jurisdiction.

The following building valuation data represents average valuations for most buildings.  Again it should be noted, when using this data, these are “average” costs based on typical construction methods for each occupancy group and type of construction. The average costs include foundation work, structural and nonstructural building components, electrical, plumbing, mechanical and interior finish material. The data is a national average and does not take into account any regional cost differences

The Square Foot Construction Cost does not include the price of the land on which the building is built. The Square Foot Construction Cost takes into account everything from foundation work to the roof structure and coverings but does not include the price of the land.

So……what is a new building’s value?

Private garages are to be valued as an IBC (International Building Code) Section 312 “Group U” utility and miscellaneous structures. V-B is the least restrictive building type with regard to materials. V-B structures can be built out of any material and it doesn’t need to be rated. It is also the most restrictive in terms of size restrictions in IBC Table 503.

A finished V-B Group U structure has a valuation of $39.83 per square foot. If the building is a “shell only”, then 80% of this value would be used ($31.86 per square foot).

Putting up a standard two-car garage 24 feet square? The valuation would be $18,351. A 30’ x 40’ shop? $38,232.

Looking at these valuations, a post frame (pole) building is a tremendous bargain, and a great way to add instant equity to a property! Get a quote on a pole building kit package, add in your other costs (HVAC, etc.) and I believe you will see dollar signs – going into your pocket, instead of out.

Things You Never Wanted to Know About Snow Load

Yes I know, it is white (at least it starts out that way).

From a design standpoint there are lots of things to know about snow loads.

Cautionary Warning: The information contained herein is fairly technical in nature. We use ALL of this information in the design of your new Hansen Pole Building. Some clients will think this is all very cool, for others, it may cause your head to explode. I’ve been waiting three decades to pass along this information to a client, as I’ve always felt the understanding of it is pretty impressive.

1.  GROUND SNOW LOAD (otherwise known as Pg). This is based upon a once in fifty year (probability of event greater than design loads happening is 2% in any given year). The use of unrealistically high Pg values causes issues with the design for drifting snow.

The International Code specifies design snow loads are to be determined according to Section 7 of a document called ASCE 7. This document provides for all roof snow loads to be calculated from ground snow loads, however not every Building Department follows this procedure. When discussing snow load with anyone, it is crucial to have a clear understanding as to if the load is a ground or flat roof snow load.

Pf is FLAT ROOF SNOW LOAD – If, as a consumer, your concern is snowfall and you want to upgrade the ability of your building to carry it, THIS is the value to increase. Often changes of five or 10 pounds per square foot result in minimal differences in cost.

Pg is converted to Pf by this formula:

0.7 X Ce X Ct X Is X Pg = Pf

2. Ce is the wind exposure factor for roofs.

For an Exposure B or C for Wind; Fully Exposed = 0.9; Partially Exposed = 1.0; for fully sheltered (e.g. nestled in tightly amongst conifer trees as an example) Exposure B = 1.2, Exposure C = 1.1 (how you could have Exposure C and fully sheltered is beyond me)

We use partially Exposed (Ce = 1.0 as a default)

3. Ct is the effect of temperature (building heating), where:

Ct = 1.0 for heated structures (climate controlled)

Ct = 1.1 for Structures kept just above freezing and others with cold, ventilated roofs in which the thermal resistance (R-value) between the ventilated space and the heated space exceeds 25h – ft^2 – degreesF/Btu

Ct = 1.2 Unheated

We use Ct = 1.2 as the default value

Most truss designers will use a Ct value of 1.0 or 1.1 in their designs. This results in a decrease in the ability of the roof to carry snow loads. These values should only be used when appropriate.

4. “Is” is the IMPORTANCE FACTOR

ASCE I is a structure which is a low hazard to life in the event of a failure. Is = 0.87

ASCE II residences and frequently occupied commercial buildings (a warehouse or storage building is probably ASCE I) Is = 1.0

ASCE III Is = 1.1

ASCE IV Is = 1.2 (these are “essential” essential facilities – police/fire stations, hospitals)

5. There is also a Minimum Roof Live Load (known as Lr) of 20 psf (defined by Code) (psf = pounds per square foot) which accounts for weights such as construction loads, when Pg values are very low.

Lr is adjusted based upon the area the roof member supports and can be as low as 12 psf, in cases where a roof member supports over 600 square feet of area.

Doing the math, it would be unusual, using the laws of physics, for Pf to be greater than Pg – however, some jurisdictions have established Lr values which defy the laws of physics (e.g. State of Oregon, where most of the state has a minimum Lr of 25 psf – exceptions being some locations along the coast, where it is 20).

From Pf, Pr (Pressure on the roof) values are calculated depending upon whether the roof is a slippery surface or not, whether building is heated or not and the slope of the roof.

The Top Chord Live Load (TCLL) of any roof trusses will be the greater of Pr or Lr.

6. Duration of Load (DOL) for Snow is typically 1.15. DOL can play a part in some snow areas, where the Building Official (BO) has made the determination snow will remain upon the roof for extended time periods. Some Examples of this include Higher elevations in Utah and Kittitas County, WA where the BO has declared DOL = 1.0. In areas with little or no snowfall (where Lr > Pr) DOL = 1.25.

Yes, I know this is a lot of stuff to carry around in your head.  Trust me, I know all too well, and my character analysis consistently reads “does not like numbers”!  All these numbers and “code requirements” are why we not only ask, but insist you must take the page of our quote with the Design Criteria to your building department to get their blessing on it, and ask if there is anything else they require.  With over 7000 building departments in the U.S., it would be the greatest feat on earth if we could keep up with all of them, and which ones change on any given day. My last caution is to be careful when asking your building department about snow load.  Be sure you keep “roof” and “ground” snow loads separate.  Because when it comes to getting your building designed, priced and finally plans signed off by your building department, there is a difference!