Tag Archives: snow load

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.

I’d Rather Order My New Pole Building Myself

We humans want to do things ourselves. We love GPS because it keeps us from having to ask strangers for help or admitting we are lost.

I admit to, at one time in my life, being an extremist at “doing it myself”.

Then I learned….. by listening to experts I could learn so much faster.

Consider me – I’ve either personally made more mistakes or been a party to helping people fix theirs, than most can even begin to imagine.

Why should you repeat these sins?

Answer: You do not have to. Here is a case in point real life story thanks to reader ARNOLD:

“It would be really neat if when filling out information your page a potential customer could get the information without having to give name, email, and what all else.  Kind of a pain in the rear if you know what I mean.

Thanks”

Mike the Pole Barn Guru writes:

Thank you very much for your input. Certainly we could have our system set up so you could go online and actually even order a building, without ever having to talk to anyone. Think of it similar to be able to custom produce a massive set of somewhat Lego® like pieces online and have them delivered. We could do it……

And chances are you would end up regretting your decision forever.

Our system would allow you to make changes in climactic design. This could result in you not having a building meeting Building Code loadings. Worst case scenarios being you would either not be allowed to build, or (in jurisdictions with no plan reviews and field inspections) your building could fail and injure or kill someone. Decrease snow and/or wind loads or chose B for wind exposure instead of C could result in both savings as well as collapses. Your building department would also reject your plans…or even worse, your building, once you had constructed it. Planning on “doing it yourself” and not ever contacting your building department? In one word: Don’t!!! I’ve seen far too many customers snagged on their buildings after they were built. Worse case, the building department made them tear it down.

About Hansen BuildingsFace it, we humans are dimensionally challenged. Even though we have an idea a basketball hoop will be at 10 feet, we think our car needs a door this height. We want to make certain you design a building with adequate spaces for your activities. This includes properly sized doors, properly spaced, to actually allow prized possessions in or out without damage to your building or something treasured.

Our having you interact with a real live person has a goal of keeping you (as much as possible) from making crucial design errors causing you to hate your pole building forever. One of those mistakes would be us allowing you, as a serious future building owner, to order a post frame building from someone else. We firmly believe we have the absolute best value in a complete, engineered post frame building kit package – enough so we offer to go comparative shop for any client prepared to invest in a building. Call 866-200-9657 and ask us about this service. It’s free!

500 Year Storm and Wind Exposure

500 Year Storm and wind exposure.

Allstate® Insurance has a TV commercial featuring actor Dennis Haysbert. Haysbert sits in an open field and questions why there have been 26 “once in 500 years storms” in last decade, when term alone implies they should only happen every 500 years.

View Allstate® commercial here: https://video.search.yahoo.com/search/video?fr=crmas&p=Allstate+once+in+500+years+storm+commercial#id=1&vid=b134fa05aba0ff046debaea22891c23d&action=click

IBC (International Building Code) in Chapter 16 (https://codes.iccsafe.org/public/document/IBC2018/chapter-16-structural-design) Table 1604.5 lists Risk Category of Buildings and Other Structures.

Risk Category I includes buildings representing a low hazard to human life in event of failure – agricultural buildings and most detached residential accessory buildings fit into this category.

Risk Category II would be most homes and many low risk commercial, industrial and manufacturing buildings.

Risk Categories III and IV cover buildings with high occupancies or are essential to fire, life and safety (like fire stations).

IBC offers Minimum Design Loads modified by a given factor depending upon Risk Category. For a previous article about this subject please see: https://www.hansenpolebuildings.com/2018/08/minimum-design-loads-and-risk/.

Reflect, if you will, back upon paragraph one above and a 500 year storm.

wind damageRisk Category I buildings are based upon a once in 25 year probability of minimum design loads being exceeded. Risk Category II once in 50 years, while Categories III and IV are once in 100 years.

So, what does one do to protect against a once in 500 years storm?

When planning your new post frame building, this becomes relatively easy – have it designed for greater loads than bare Code required minimums. While this sounds simple, very few clients consider asking for it and even fewer post frame building sales people offer it!

Why would it not be offered?

Price

People are selling buildings using price rather than value.  Most are afraid to suggest increasing building price by a few percentage points, because they think it will cost them a sale!

I know there are numerous members in our post frame industry who are reading this article. To you I offer this challenge – as an option start offering to every potential client an ability to have their building designed for an extra even five or 10 psf (pounds per square foot) of snow load (in snow country of course). And, give them an option of withstanding greater wind speeds than Code minimums. Even upgrading wind Exposure B sites to Exposure C will increase ability to resist wind loads by about 20%.

A short wind exposure story can be found here: https://www.hansenpolebuildings.com/2011/11/wind_exposure/.

Now, sell your potential client benefits of having last building standing when Mr. Haysbert’s storm rolls through.

Sold itself, didn’t it?

 

Builders Who Make No Upgrades in Twenty-Five Years

Builders Who Make No Upgrades in Twenty-Five Years.

Why?

We’ve Been Building This Way for 25 Years
In the event you happen to hear this from a pole builder – run away from them as quickly as possible.
Why?
Because every three years there is a new version of the Building Codes and often those new Codes come with changes in the way wind, snow and or seismic loads are applied to the building. New methods and materials seem to appear on the market so fast they make one’s head spin. Technology moves at a breakneck speed and to be doing things exactly the same for 25 years means your proposed erector is pre-internet in thinking!!

COREY in BILLINGS writes:
“Good Morning,
I was speaking to Rachel and she gave me your email to see if you might be able to answer a question for me. I hired complete a 50’x 80’ x 12’ pole barn here in Huntley, MT. The company showed up on the job yesterday and drilled the holes and started setting posts. Posts are 8’ center. They set the corner posts and maybe 6 sidewall posts and 4 endwall posts. The other posts were placed in the drilled holes and left for completion today/tomorrow. When I inspected the posts that were placed but not set (no backfill) I noticed that there was no footing or no cleats attached to post base to prevent uplift. When I questioned the owner of the company what he was using for footings he stated nothing added just solid tamped. I immediately called him and questioned his reasoning and got the I have been building these like this for 25 years. My question is on average what is the post load in psi on the 50’ x 80’ x 12’ pole barn with a 40# snow load? My soil has a bearing capacity of 2100 psi.”
In my humble opinion, you need to stop them immediately. Just because they have been doing them this way for 25 years does not make it correct.

Mike the Pole Barn Guru Writes:

Assuming a 40# design roof snow load and minimal design dead loads (usually 3.3 psf top chord and 1 psf bottom chord) gives a total of 44.3 psf X 8′ on center X 50’/2 = 8860# downward If they are using 6×6 posts (5-1/2″ nominal) they are placing over 42,000 psf on the base of the column!!

Roughly 21 times the soil bearing capacity.

Each post should probably have a concrete pad 30 inches or so in diameter underneath and at least 6 (if not 8) inches thick.

If I were you, I’d be requiring the building contractor to submit engineer sealed plans for your building to you (even if you have to pay for the cost). Otherwise you are pretty well hung out to dry.

Panic Mode! We’ve All Been There

When Clients get into Panic Mode

Most of us have been there with a major purchase – we were all excited about it and then somewhere before it gets delivered we start to second guess ourselves.

Here is an example:

Dear Mr. Xxxxxx ~

Thank you for your investment into a new Hansen Pole Building.

You wrote:

“When I originally talked with Mike I wanted a heavy duty building, It seems no one there was listening, I have my plans and the roof trusses show 2×4 construction and side posts 3.5 x 5.5,  I am very concerned that this is a very weak design. I know I already approved the plans but I will have to spend about 4000.00 more to locally to purchase 6×6 posts and 2×6 trusses. I guess I can sell the ones I receive.  You people must think I live near Seattle, not, I live on the eastern slope of the Cascade Mountains, your 2×4 double truss design appears obviously not strong enough to take the snow loads in my area. I am very concerned.” 

 (FYI – the “Mike” referenced is Hansen Pole Buildings’ Designer Mike Houska)

My response:

We take our client’s concerns to heart, it is part of why every Hansen Pole Building is structurally designed by a registered professional engineer.

In review of your building plans, I see it has been designed to meet or exceed a roof snow load of 45 psf (pounds per square foot) as well as an ultimate wind speed of 100 mph (miles per hour). The calculations for each and every member and connection on your building have been thoroughly reviewed by a Registered Design Professional (the engineer who seals your plans). I would venture a guess your Building Department has approved the plans as meeting the structural requirements.

The prefabricated roof truss designs for your building utilize 2×6 1650msr (or stronger) lumber for the top and bottom chords. When you go to your local lumberyard to purchase a 2×6 graded as #2 (the standard for framing throughout the industry), it has a bending strength of from 1105 to 1170 psi (pounds per square inch), depending upon the species of lumber. The 1650 msr being used for your truss top and bottom chords is at least 41% greater in bending strength. The interior members of the trusses (the webs) are indeed 2×4, as they would be in virtually any truss design. In truss configurations, the webs carry minimal loads for both compression and tension and are loaded to only 75% of their capacity on the interior double trusses. If your trusses have not yet been fabricated, it is possible we could upgrade to 2×6 webs, however the load carrying capacity of the trusses would not be increased by this change – you would basically just be spending money to spend money.

On to the column sizes. I’ve written extensively in the past on why a 4×6 (3-1/2″ x 5-1/2″ actual) sized column will outperform a 6×6 column in most cases. If you would kindly take just a few moments to read about it here: https://www.hansenpolebuildings.com/2014/08/lumber-bending/.

Things I do know – your building, built according to the engineered plans, will support the loads given, not only is it an engineered building, but we also provide a limited lifetime warranty to back it up!

I did a few trial calculations, increasing your roof snow load to up to 180 psf (four times what you invested in). Even at this load, 4×6 columns still work! The column is not “the weak link”.

Provided your lumber package is not ready to be shipped and your trusses have yet to be fabricated, it might yet be possible to increase the design roof snow loads, and/or the design wind speed beyond what the Code requirements are. In doing so, this again checks every member to insure you have no weak links.

If you desired to increase both by 25% (Ground snow load to 75, roof snow load to 56.25 and Vult to 112 mph) you would be looking at an up charge of $1580 and would receive new sealed plans and truss drawings to confirm these loads. An increase of 50% (Pg = 90, Pf = 67.5, Vult = 122.5) would be $2765. Either of these would, of course, be depending upon the status of your building in the production processes.

We will await hearing back from you as to your wishes.

Some notes – the increase in wind velocity does not increase in a linear fashion due to there being a square of the velocity in the calculation between wind speed and load being carried. If you have a concern about the adequacy of the loads being called about by your local Building Officials, we can quite easily give ideas as to what your added investment would be to increase either snow or wind loads. In many cases the difference is small in relationship to the total price of your building and peace of mind is always a bargain!

Mike the Pole Barn Guru

When is it Time to Remove Roof Snow?

Regardless of what side of the climate change argument one is on – it has been snowing in Massachusetts this winter.

A lot.

Late January’s Winter Storm Juno alone brought up to 36 inches of snow in some parts of Massachusetts. https://www.weather.com/storms/winter/news/winter-storm-juno-snow-totals-wind-gusts

As if Juno wasn’t enough, another storm followed – leaving so much snow on the ground it forced the postponement of the celebratory parade through Boston for the Super Bowl Champion New England Patriots. https://www.cbsnews.com/news/flash-freezing-now-the-big-concern-in-northeast/

So, how much snow is too much for one’s roof?roof snow

As a basic rule of thumb, consider saturated snow weighs in at approximately 20 pounds per cubic foot. This weight is based upon a 25% moisture density, which may be conservative or liberal, as the actual moisture content of snow can range from approximately 1% to 33%.

Using the 20 pounds per cubic foot, this means every inch of snow will add 1-2/3 pounds per square foot of weight!

Any ice build-up on roofs would need to be added in as well. Use 5.2 pounds for each inch of ice depth.

For those who want to get scientific, the actual roof snow load can be checked by cutting a one foot square the full depth of the snow and ice build-up on the roof, dumping into a plastic bag and weighing the contents.

Modern buildings are designed for a snow load which assumes the roof snow load will be exceeded anywhere from once in 25 to once in 100 years, depending upon the Risk Category of the structure. The actual International Building Code language on risk categories can be read at: https://publicecodes.cyberregs.com/icod/ibc/2012/icod_ibc_2012_16_par023.htm

Buildings which were not constructed under Code requirements are often at far greater risk to collapse under snowfall. When rain falls upon snow, the weight of the roof snow can increase rapidly. Heating a building, in an attempt to melt the snow off a roof, can result in ice dams at the eave sides of the building – compounding the load problems.

Please be aware of the potential dangers of shoveling or raking snow from a roof. Besides the potential damage to the roofing materials and structure, there are such factors as a person sliding off the roof, falling off a ladder, overexerting themselves, or injury from snow sliding on top of them.

I can’t make recommendations on when to remove snow from any particular roof. It is up to the individual building owner to consider the benefits and dangers of snow removal and determine their own course of action. If your structure is in question, it is always best to consult a registered professional engineer.

Under-Designed Ag Buildings

Does Anyone Else See How This Could Be a Problem?

Eric, one of the owners of Hansen Pole Buildings, had me check out a website today for a pole building supplier who is extolling the virtues of a particular “nailed up” laminated column, which has been the subject of some discussion in my articles. https://www.hansenpolebuildings.com/blog/2014/04/titan-timbers/

This particular supplier took verbatim the information provided by the nailed up column suppliers, without questioning the validity of the data supplied.

Me, being the curious sort, took a cruise around the pole building supplier’s website.

WHAT I SAW MADE BLOOD SQUIRT OUT OF MY EYEBALLS!!

“Snow Loading                                                                                   

Xxxxx Buildings commitment to quality is second to none. This is amplified by the fact that all buildings meet or exceed the MN State Building Code. Xxxxx Buildings provides all customers ‘peace of mind’ by making sure the roof system loading for your building will keep you protected from natures elements. The roof system loading includes the trusses and the roof purlins.”

Now I am all over this! I appreciate people with a commitment to high quality and excellence in pole buildings. “…all buildings meet or exceed the MN State Building Code” is way cool….

Hay Storage BuildingUntil I read their next paragraph:

“Ag Buildings
There is no code regulation of Ag buildings, (these buildings are exempt from the code) but suggested minimum loading would be 25 psf or 30 psf live load on the roof system. The definition of an Ag building would be a structure on agricultural land designed, constructed, and used to house farm implements, hay, grain, poultry, livestock, or other horticultural products. This structure shall not be a place of human habitation or a place of employment where agricultural products are processed, treated or packaged, nor shall it be a place used by the public.”

From one side of their mouths is “all buildings” meet Code, and out of the other – they are providing “ag buildings” with loads below Code!!

Here is the Minnesota State Snow Load map: https://www.dli.mn.gov/CCLD/PDF/bc_map_snowload.pdf

To get from a Pg (ground snow load), to a roof snow load, involves the multiplication by several factors. Learn more than you ever wanted to know here: https://www.hansenpolebuildings.com/blog/2012/02/snow-loads/

For discussion’s sake, we will assume these Ag buildings are unheated (most unoccupied buildings are) with the most common 4/12 roof slopes and steel roofing. The roof truss top chord live load under this combination should be 34.7 psf with 50 psf for Pg.

This provider’s, “suggested minimum loading would be 25 psf or 30 psf of live load on the roof system” is under designing these roofs to support snow by at least 13% and as much as 40%!!

You don’t own a farm, so what do you care?

When those under designed roofs collapse and the insurance companies pay to rebuild – it is YOUR insurance rates which are going to increase!

And if you do own a farm, I’d hate to be the one cleaning up the mess when your roof caves in…and hoping you are not in it when it does!

 

Dear Pole Barn Guru: How to Replace a Sliding Door with an Overhead

New!  The Pole Barn Guru’s mailbox is overflowing with questions.  Due to high demand, he is answering questions on Saturdays as well as Mondays.

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday or Saturday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

 

DEAR POLE BARN GURU: Have pole barn with sliding doors which are being wedged with weather changes. Looking for overhead door option for door that is 16′ wide and 12′ tall. Do you provide these and conversion labor to install? LOOKING IN LEBANON

DEAR LOOKING: Switching from sliding doors to an overhead door is going to pose a massive challenge to do correctly. This, in itself, is reason enough to spend the generally few dollars up front to use a sectional steel overhead door.

To begin with, the openings are not framed to the same size. It is easier to frame smaller than have to try to hack out and replace one or more columns. This will probably entail framing down to a finished hole 13’10” in width and 10’11” in height (measured from the top of the concrete floor) and installing a 14’ x 11’ residential overhead door. In order to get things looking right from the outside. All of the steel on this wall should be replaced, to give uniform color and no splices.

We can certainly provide a wall’s worth of steel siding, color matched powder coated screws, the appropriate steel trims, the overhead door and hardware to hang it. We are not contractors in any state, so we do not and cannot provide any labor to install.

You may want to look at what the real problem is – sounds like you have frost heaving, which is pushing the ground, or concrete, up at the location of the door. Just switching doors is not going to take away the problem.

If heave is the root cause of the problem, then remedial action can be taken by installing a French drain along the side of the building in front of the door. The sliding doors can also be taken off, and their overall height shortened enough to keep them from binding when the heave occurs.

DEAR POLE BARN GURU: How do I calculate what size of purlin I need based on my snow load, and the bay spacing of my pole barn? Thanks. CURIOUS IN CULDESAC

 

DEAR CURIOUS: From the ground, a roof purlin looks pretty simple – it is usually a piece of 2x material, fastened on top of or attached to the side of rafters or roof trusses. Roof sheathing (typically OSB – oriented strand board, plywood, or steel roofing) is then attached to the top of the purlins.

Purlins are not simple at all. They must carry all applied dead loads, live loads from snow as well as wind loads. They need to be checked for the ability to withstand bending forces (both compressive and from uplift), to not have too much deflection and be adequately attached at each end.

In snow country, purlins near the roof peak need to be checked for the added drift loads which are applied.

I could spend several thousand words and numerous pages to teach you how to be able to properly calculate the purlins for your individual case, however it is far more information than the average person wants to, or is able to, absorb.

The best recommendation – hire a registered design professional (RDP – architect or engineer) who has the ability to run the calculations to adequate design your purlins based upon the climactic (wind and snow) loads being imposed upon them at your building site. Or better yet, order a complete pole building kit package which has been designed by an RDP.

Building Code: Or Not?!

Things Which Scare the Pooh Out of Me

And we are not talking about things which go bump in the night or hide in closets waiting to jump out.

Hansen Buildings’ Designer Rick recently ran up against an interesting situation.

One of the responsibilities of clients is to verify the code information with their Building Department prior to ordering. As there are, at times, only questions which can be answered by the client, we have found it to be the best solution for all involved if the client checks out building code requirements with his local jurisdiction.

Building Code Snow LoadsThis particular client lives in the far northern United States, where it tends to snow…a lot.

Client does his part and gets this response:

“We don’t enforce the building code in Xxxxxx County, so you will have to have whoever designs your building refer to the xx State Building Code. We have a link for that on our County Website it is as follows: xxxx”

So Rick gives it a try and comes back to me with:

“You are sure right on this.  I just got off the phone with the county.  He actually used the words “we don’t care if it is built of straw” as long as your setbacks conform. 

This is my first encounter with a county that doesn’t even have a snow load, and I didn’t think there were any.

The link in the e-mail below gives me an error code and the link on the county web site for the XX State Building Code gives me Chinese.”

Now this particular building is going to be constructed where there is snow in the winter….lots and lots and lots of snow.

Personally, I am not a fan of government intervention, however I am a fan of people not being hurt or killed when under designed buildings collapse.

For people who are going to build in areas where the Building Code is not enforced – do due diligence, make every effort to find or calculate loads which will be adequate for your structure.

If you need help understanding your local building code, ask me.  I’m all about safety first.