Part of the mission of any good post frame (pole) building kit package supplier or contractor should be to save the client from making crucial design errors which they will later regret.
Among the most often questions I answer in my “Ask the Pole Barn Guru” weekly column is in regards to the ability of an existing building’s roof trusses to carry a ceiling load. I’ve expounded in this area in the past:
https://www.hansenpolebuildings.com/2013/03/ceiling-loads/
With a client who possibly did not communicate their needs well: https://www.hansenpolebuildings.com/2015/04/ceiling-load-2/
Existing buildings: https://www.hansenpolebuildings.com/2013/10/ceiling-load/
This morning Hansen Pole Buildings’ Designer Dennis asked a question of me which I had failed to address in the past 1000 plus blog posts, “I was looking on blogs couldn’t find difference between roof trusses designed for ceiling load and not designed”.
Like most anything here at Hansen Pole Buildings, ask the question and ye shall receive an answer.
Increasing the ceiling load carrying capacity of a roof truss can result in one or more of many changes. Generally there will be more changes to the physical nature of the trusses as the span of the truss, or roof snow loads increase.
Here are some of the things which might change:
Grade of lumber. The #2 grade lumber which one might acquire at the local big box store or lumberyard is rarely strong enough to be used in most truss chord applications. Most generally one finds the use of #1 or Select Structural visually graded material, or what is known as machine graded lumber (https://www.hansenpolebuildings.com/2012/12/machine-graded-lumber/). Often the need for increased load carrying capacity can be accommodated by a step or two up the ladder in the strength of the lumber.
Sometimes, stronger lumber alone, will not be the cure and larger dimensions of lumber may need to be utilized. 2×8 instead of 2×6 as an example.
Truss webs – those internal pieces of the truss, the ones running at angles between the top and bottom chords are known as “webs”. Sometimes the extra load capacity can be gained by adding more webs to the truss.
And let us not forget the lowly steel connector plates, which hold prefabricated metal connector plated trusses together. All of those joint connections now have to take an increased load, so there is going to be more square inches of steel utilized to do the trick.
The important part is less about HOW the load is going to be carried, and all about the ABILITY to carry it. Considering a new post frame building? If you think either you or the next owner or owners of the building might ever consider adding a flat level ceiling in the building, then it would be prudent to (at the least) order trusses designed to support the load now.
This is not the place to scrimp out trying to pinch a few pennies!
The following describes 2×6 SYP #2 purlins spanning a 14′ bay, with an on-center spacing of 24″ (s
I spent two decades in management or owning prefabricated metal connector plated wood truss plants. In my humble opinion – attempting to fabricate your own trusses of this magnitude is a foolhardy endeavor, for a plethora of reasons:
DEAR MARK: Your roof purlins appear to be adequate to support this type of a snow load. As to trusses, I would reach out to Morton Buildings with your site address and they should be able to pull up truss drawings for your building. If not, you would need to retain services of a Registered Professional Engineer who could do an actual inspection of your trusses and run calculations to determine exactly their capacity.
DEAR ANDREW: Can and should are not often same.
DEAR DAVE: Unless your window’s vinyl frame was actually damaged, in most instances a glass company can do a repair of just broken glazed portions. I would suggest a call to Capital Glass in Reno (775)324-6688 as this appears to be in their wheelhouse and they service Fernley.
We typically would use 2×6 #2 on edge for these recessed (between truss pairs) roof purlins. Here are the calculations:
As we see in Chapter 1 of the Post Frame Building Design Manual (PFBDM), post frame construction has been around for hundreds of years. The performance, life expectancy, and reduction of material and labor costs are all reasons that this type of construction is becoming more popular today. We see not only construction in agricultural settings, but residential construction is rapidly growing in today’s price and time conscious market. However, structural design is critical to ensure long life and adequate performance of the building. 
This is just one of many reasons why post frame buildings should be designed by a Registered Professional Engineer. 
Well John, you have left out a crucial part. One no proper pole barn should be without. Plans designed and sealed by a Registered Professional Engineer specific to your building at your site. To build without them is, in my humble opinion, fool hardy and I cannot endorse your plan of attack or methods of construction without them. Outside of this – attempting to field construct your own roof trusses is not a good choice. Prefabricated trusses are truly a bargain, especially when considering risks involved should your home made trusses collapse injuring or worse killing you or a loved one. 
Face 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.
Risk 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.
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.”
Until I read their next paragraph:
