Tag Archives: embedded posts

Engineering an Open Pavilion

Engineering an Open Pavilion

Professional Engineer KEN in AIRVILLE writes:

Working on engineering a post frame equipment open pavilion 28×48. Only has 2 posts on the front wall and big ass flat girder for a header. See attached plans. I have done them all different ways before I a structural engineer who grew up at my father’s sawmill and been in the engineering and framing for 30+ years. Been reading your blogs especially all the info on knee braces. I agree the skin gives you 90% of lateral capacity over embedded posts or knee braces. But that is pretty much all we have to use on an open structure. I didn’t really want to use buried posts for longevity but may be best for lateral capacity. I only have 2 columns in the front holding the roof up so I wanted to come out of the ground with a big ole concrete pier in case it ever got impacted. Would love to discuss post frame design theory with you. One of your guys used to be a truss designer also I read somewhere. I know that industry very well been in it my entire life. Have a great day.”

Mike the Pole Barn says:

Thank you for reaching out and for forwarding your draft plans.

I was in ownership or management of prefabricated wood truss facilities for over two decades, in my “past” life.

Unless there is some strong objection, embedded columns are probably going to provide your best design solution, as well as being easiest to construct. You will want to specify UC-4B for treatment, as this should assure a lifespan greater than our grandchildren’s grandchildren.

If bracket mounts end up being your solution, look at using Sturdi-wall Plus brackets, as they have a far greater moment resisting capacity than do Simpson products and have an ICC-ESR approval.

I would look at placing low side columns every 12′, using a pair of trusses ganged together and notched into columns, with 2x purlins recessed between top chords, in Simpson hangers.

On high side, parallel chord flat trusses could be used for your ‘beam’, also notched into columns. Mono truss top chords could be run across top of trussed beam and look at making connection between mono trusses and beam a fairly stiff one.

Explore using full length treated glu-lam columns, without knee braces. Your knee bracing challenge is two-fold – you have to deal with forces being put into trusses by knee brace and toughest – coming up with a connection adequate to be able to transfer those forces. Your column sizes will be dictated by L/d ratio, so even if your knee braces were to work in the direction of truss span, you still have slenderness in length of building. It looks to me like a 6 ply 2×8 glulam from Rigidply (7″ x 8-1/16″) should be capable in both directions.

In order to not void roof steel paint warranty, look at a roof slope of 3/12 with an Integral Condensation Control factory applied to prevent condensation drippage.

The NFBA has available a Non-Diaphragm Design Guide (https://www.nfba.org/aws/NFBA/pt/sd/product/14888/_PARENT/layout_details/false), it may prove helpful for this project.

Continuous Foundations, Column Spacing, and Inside Closures

Let’s finish off the week with one more day of Ask the Pole Barn Guru. Today Mike takes on reader questions about connection with a continuous foundation, benefits of 10′ or 12′ column spacing, and replacing inside foam closures.

DEAR POLE BARN GURU: Hello. We are located in Ohio. We would like to build a 24×40 pole building. Zoning says it needs to be attached per their rules so we plan to attach with a simple fabric awning to meet zoning. The county says we need a continuous foundation if it is considered attached. Stupid right? The only thing touching both building will be a fabric awning. I have been told we can have an engineered foundation, or a 6″ by 38″ deep concrete wall poured, wood foundation or a traditional block foundation. Where would I begin to find details for an engineered foundation? I am struggling finding the info and where to start. RALPH in POLAND

DEAR RALPH: In a typical fully engineered post frame (pole) building isolated columns embedded into your ground would be complying and meet Building Code requirements. We would like to see your jurisdiction’s written requirement for mandating a continuous foundation, as often times these ‘requirements’ are just one person’s own feelings of how things should be done, rather than having an actual basis.

Should this indeed be an approved statute, we can have your new building engineered with your continuous foundation of choice. One of our Building Designers will be reaching out to you to discuss further, or dial 1.866.200.9657 for immediate service.


DEAR POLE BARN GURU: Are there any benefits going with 10′ centers over 12′ centers? I was thinking about going with 10′ centers because in my mind it seems like that would be a stronger building and would have less purlin sag over the years but rather go with 12′ centers to gain more parking space for a leanto? Any recommendations? Thanks BRIAN in PARRISH

DEAR BRIAN: Regardless of spacing of columns or trusses, a fully engineered post frame building will be designed to meet or exceed a specified set of wind design criteria – speed and exposure. You are better served to increase design wind sped, so your entire buildings is capable of supporting higher loads, than to merely move columns closer together. Provided Code required deflection limitations have been properly engineered for, any purlin sag, over time, should be relatively imperceptible.


DEAR POLE BARN GURU: Greetings, My metal roof is 15 years old and the inside foam closures have deteriorated.  1.  Are they necessary, and 2. if so, how does one replace them?

I hate to remove the screws along the eaves (or maybe even more screws farther up each panel), but see no other way to get replacement closures under the metal panels.

I’d appreciate any advice


DEAR SHERRY: Properly manufactured inside closure strips are UV resistant and should outlive your building’s steel roofing. Personally, I find them essential, as without them small flying critters have a clear path to enter your building. In order to replace them, you will have to remove screws along your eave line. Once remains of old closures are removed, new ones can be put in place. Old screws should be replaced by both larger diameter and longer screws, to maintain integrity of connections and prevent leaks.

For extended reading on Inside Closures https://www.hansenpolebuildings.com/2015/12/the-lowly-inside-closure/



Overhead Door Replacement, Building Instructions, and Strong Columns

Replacing and overhead garage door, instructions for a pole barn, and the use of “Strong Columns” in today’s Pole Barn Guru!

DEAR POLE BARN GURU: Looking to perhaps replace my 10 wide by 8 tall overhead pole barn door with a 10′-10′. Along with chain pull down. What options do you have or suggest. It’s nothing fancy. Thanks. Need the track or some sort of extension that goes with door as what I now have would be too short if I’m thinking correctly. BRIAN

DEAR BRIAN: Done right, this is going to take someone who can visit your site and do an analysis of the situation. Your best bet is going to be to contact a local to you overhead door installation company. The main concern would be how much room you have to go “up” for a taller door. You’ll need the proposed door height, plus about 15″ from the floor. 


DEAR POLE BARN GURU: We have a customer that is looking for installation of a 24×36 Metal Barn, we would like to inquire if you have any installation instructions. Thank you. JEAN PAUL in FORT MYERS

Hansen Buildings Construction ManualDEAR JEAN PAUL: Every Hansen Pole Building kit package comes with not only a two complete sets of engineer sealed site and client specific 24” x 36” building plans, but also our industry leading Construction Manual. Some example plans can be viewed here: https://www.hansenpolebuildings.com/sample-building-plans/.


DEAR POLE BARN GURU: What are your thoughts on the Strong Column by Strongway Systems? Very appealing that it’s adjustable height, has brackets for skirt and keeps the post out of the ground. I’ve read you auger the hole, place these (no need to pour footer), square, attach skirt, then fill hole with concrete and attach wood columns. JOE in PORTLAND

DEAR JOE: Strong Columns are no longer available, as the manufacturer has ceased production.

My personal preference is the low tech, lowest cost version – properly pressure preservative treated columns embedded in the ground.

For those who absolutely must have columns above ground (keeping in mind they will last virtually forever https://www.hansenpolebuildings.com/2017/12/will-poles-rot-off/), I would personally backfill the holes with concrete and utilize wet set brackets designed for post frame construction (https://www.hansenpolebuildings.com/2017/05/sturdiwall-brackets/).


Coulomb Theory

As I have probably mentioned a few times, I learn new stuff every day. Sometimes, what I learn causes me to rethink my prior positions on subjects. I’d like to believe this is a good thing, as it keeps me from being so rigid.

Concrete Form TubeI’ve always had a bad attitude toward the use of sonotubes placed in holes of post frame buildings. People’s thought is generally – I have dug a very big hole, I don’t want to use so much concrete in the hole, so I will put a sonotube in the hole, and backfill around the tube.

I’d always looked upon this rather like the ancient Roman adage, “It’s all fun and games until someone loses an eye”. To me, it was all fun and games until the pole building column and the sonotube get sucked out of the ground like a cork from a champagne bottle.

What started me on this particular trek was doing frost heave research. I’d read some work done by engineer Harris Hyman, who appears to be the expert on the subject.

I am reading along in one of his papers, where he is talking first about anchoring a post to an oversized footing to prevent uplift. The idea is that the weight of the earth above the footing will hold the post down, and if the footing is sufficiently deep (like below the frost line), no heaving will occur.

Well, Harris has another idea:

There is another option that may have more promise for post construction: Forget the footing, but put the post in deep enough to resist lifting by the friction of the earth. The earth exerts a lateral – sideways – force against the surface of a wood post or sonotube. Friction between the earth and the post causes the post to move with the earth. As the post goes deeper, the lateral force of the earth increases, creating greater and greater friction against the sides of the post and holding it in the ground.

The Coulomb theory of earth pressures shows that the friction against the bottom third of the underground portion of an embedded post is equal to the friction against the top two-thirds. By this reasoning, if the post is not to move, the bottom one-third (or a little more) must be below the frost line. With a 4-foot frost line, a 6-foot or deeper post depth is needed, so that at least 2 feet, or one-third, of the embedded part of the post is below the frost line.”

Now, please keep in mind, Mr. Hyman was writing only in regards to combatting forces from frost heave, however the same theory of earth pressures could be used to resist wind uplift as well. An important factor in calculating the needed embedment of columns is the square of the dimension of the column (or its concrete encasement). If an unencased column was used, the depth would end up being proportionately greater than one with concrete backfill.