DEAR POLE BARN GURU: I have read much debate about setting the poles in concrete with no “footing” beneath them vs. setting the poles on a concrete footing and back filling with gravel and earth. Seems to be an issue of rot. What do you recommend? MYSTIFIED IN MAGNOIA
DEAR MYSTIFIED: It seems you and I have been reading the very same posts on advice boards all over the internet!
Let’s start with the “no footing” concept. Typically the soil is not able to resist applied vertical loads when those loads are transferred through the post alone. Therefore, the post is set on some type of a footing, which in the case of post-frame construction is usually concrete.
Footings must be adequate in area (radius squared x pi) to prevent the building from settling under not only the weight of the structure itself, but also the load from snow or minimum live load requirements. They must also be thick enough, to prevent the column from punching through the footing.
Considering even a fairly small span building, with minimum loads requires a footing diameter of 18 inches or more, it is fairly impractical to think of a material other than concrete which could be placed affordably beneath the columns.
On to the “rot” issue. Chapter 23 of the IBC (International Building Code) requires wood in contact with concrete to be either “naturally durable” or pressure-preservative treated. This, in itself, tends to take away credence from the “concrete rots treated wood” faction.
I know every major post frame building company in America. I have yet to have any of them report of having a single “properly treated post” rot off.
The clincher in this is “properly treated post”.
When the first IBC was published in 2000, Section 1805.7.1.2 stated, “Wood poles shall be treated in accordance with AWPA C2 or C4. This language remained the same in the 2003 IBC. The AWPA C2 and C4 standards have been withdrawn, therefore are no longer applicable or referenced standards in later editions of the Code.
In the 2006 IBC, however, things changed. Section 1807.7.1 states, “Wood poles shall be treated in accordance with AWPA U1 for sawn timber posts (Commodity Specification A, Use Category 4B)”. In the 2009 IBC (and repeated for the 2012 edition), the language remained the same, however the referenced section of the Code is now 1807.3.
What this means to you or the average consumer who is shopping for a new pole barn? Everything!
Take a visit to the local lumberyard or big box lumber store. Take a walk through the pressure treated lumber department. Every piece of pressure preservative treated lumber has a tag on it. This tag identified who the pressure treater was, as well as the level of pressure treating. Sadly, most of the pressure treated posts will be treated only to UC-4A…which does NOT meet with the Code requirements for use in pole buildings!
What this means is there are a plethora of buildings which have under treated columns, which is responsible for the rot issues, not the proximity to concrete.
Every time I have someone try to foist the “concrete rots treated wood” story on me, I ask them to show me a single laboratory test, which proves their point. None exist.
The best solution – and my recommendation – use a properly treated post, backfilled with pre-mix concrete in a monolithic pour. Place a minimum of six (and better eight) inches of concrete below the column and eight or more inches up the post (this is known as a bottom collar).
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Has there been enough history with non CCA treated posts to know if they will last in concrete or dirt? Why not just use a concrete footing and post base since the buried post contributes very little to the stiffness of the building?
Great website! Thanks!
In most cases, the chemicals which are used for preservatives are the same as or similar to CCA, just without the arsenate. Most of the compounds have been used for treating for a number of years and have been rigorously tested. The buried column actually provides for the moment (bending) resistance is an embedded system. We’re currently aware of only one bracket which is capable of withstanding those rotation forces, and it is not an inexpensive part.
What is the bracket to attach a pole to a contrete footing above the ground level, and how expensive is it?
Nick ~ Here is an article I wrote about the brackets: https://www.hansenpolebuildings.com/blog/2012/09/concrete-brackets-2/ For pricing, contact Eric@HansenPoleBuildings.com with size of columns you are using, quantity and where they will be shipped to (as well as you need wet set brackets).
buried posts in fact do contribute a great deal to a buildings stiffness
In combination with proper attachment to a concrete slab on grade, embedded columns also reduce the amount of wind shear forces roof and endwall have to carry by 25%.
I have the same question and will add, how about coated or dipped posts set in concrete?
Properly pressure preservative treated wood (UC-4B rated) will outlive your grandchildren’s grandchildren. Coating or dipping posts may make you feel better, however are unlikely to add to longevity.
When you pour the poles in monolithically is the shrinkage of the footing below the pole something to worried about? The 1/16″ gap would eliminate end bearing until the load increased to shear the friction from the pole to the encasing concrete.
Also when pouring the poles in are the blocked up off the bottom to be able to pour monolithic?
No, it is not something to be worried about. You may want to read further: https://www.hansenpolebuildings.com/blog/2013/04/pole-barn-post-in-concrete/
Many Building Departments look to have concrete below the base of the column, so the easiest method is to “float’ the column in the hole so a monolithic pour will encase the entire base of the column. https://www.hansenpolebuildings.com/blog/2014/05/one-pour-reinforcement-cage/
I am planning on installing a heated therapy pool at our home and want to enclose it for full year use. We live in central PA and code requires a substantial frost depth footing. I am trying to find the least expensive and yet durable way to enclose the pool. I will need to insulate the building and plan to have scissors trusses to allow me to ventilate the structure more easily.
If I use a pole structure, I am not sure how to ensure the inside floor will not heave with freezes and thaws. I was planning to use a poured concrete floor
My other option is to install a regular foundation and build up from there. Obviously that will increase costs substantially–6 to 10 thousand dollars I suspect.
what would you suggest for the best long term option. Thanks.
Any thoughts on this
USING 5FT SLELVES ON BOTTOM OF 6X6 POSTS FOR ROT SET A 10 INCH CONCRTETE PAD AT THE BOTTOM THEN BACK FILL WITH GRAVEL OR STONE IS THAT OK TO USE
The scenario you describe is probably inadequate to prevent uplift. You should confer with the RDP (Registered Design Professional – engineer or architect) who designed your building’s plans to verify adequacy.
THE POLE BARN THAT I BOUT COMES WITH A PLASTIC SLEEVE OF SOME SORT TO PROTECT FROM ROT SHOULD I SET IT ON A CONCRETE PAD AT THE BOTTOM OF THE HOLE AND BACK FILL WITH GRAVEL
Yes, it should be placed on an adequate concrete footing pad. A provision for uplift also needs to be accounted for. These are items which will be spelled out on the RDP (Registered Design Professional – engineer or architect) sealed plans for your building.
Saratoga wyoming Customer is wanting to build a Morton pole barn house wondering about no footings slab on grade with hydronic heat very expensive would hate to see something happen to tubing for heating
Post frame buildings do not require a continuous footing and foundation. Columns do need to extend below the frost line and be adequately concreted in. Most important will be adequately preparing your site to avoid frost heave issues. Search on our website for “frost” and “site prep” for more information.
Hello and thank you for this site.
Concerning posts for a pole barn would .40cca treated be good vs. the stuff at home depot?
.40 CCA does not meet Building Code requirements and should not be used in ground.
Hi, thank you for all the information, here is my question. Is there anything wrong with the following idea except for the concrete “waste”.
In either a home or shop pole barn build
Phase 1) at each of the column locations, pour the appropriately sized pier down to below frost line, with square tops that are at the level of the slab (when it would be finished). leave rebar sticking out the sides where the slab will be poured.
Phase 2) Pour the slab
Phase 3) Mount brackets onto pier locations, attach the columns/posts to brackets
Keeping in mind that the specifics would be done by an engineer, but mostly i’m thinking about the concept. It seems like Metal buildings are built this way, at least the ones I have seen in WNY. The main reason I would be inclined to do this is so that I could do it in phases that may be months apart from each other, as well as having a nice solid slab for other needs as well as to work off of. Thank you
By doing proper insulation techniques around the piers, you can actually avoid having to dig down to frost depth and reduce your needed amount of concrete. Wet set brackets should be poured into the piers at this point, with the “flat” of the bracket 4-1/2″ above the top of the pier.
In Step #1, when your pour your slab, top of slab should be 1″ below the flat of the wet set brackets.
Many people prefer to wait on pouring their slab – anything dropped onto a new slab has the potential to chip it, especially steel tools (like hammers). By waiting to pour the slab until the building shell is completed, you can pour out of the elements.
What size pier holes need to be drilled do when doing a free span bolt up arena say 100x200x18 ?
You will need to have these calculated by an engineer, as we do not provide PEMBs (bolt up steel buildings).
Can you put concrete in after pole barb is up and how to do
Concrete footings would be a challenge to place after your building is up. You would pretty well have to support each column, excavate to six to eight inches below the column, pour the concrete pad, then backfill the excavation, being sure to adequately compact the soil as you backfill. Moral of the story – so much easier to do it right the first time.
Question- looking at a modest single story Post Frame metal home. This is clay expansive Texas dirt. The builder is looking at using 5×5 PT post 3’ down (frost line 12”) filling with concrete. Finish building – add a floating slab. Do you see issues with this? Do we need sleeves on the poles?
Successful building on clay does come with its own set of challenges https://www.hansenpolebuildings.com/2020/07/barndominium-on-expansive-soils/
5×5 columns are actually not very strong, I would discourage their use unless your builder can provide engineer sealed drawings specific to your building’s dimensions and features with the correct design wind speed and exposure.
Properly pressure preservative treated columns (UC-4B rated) do not require sleeves.
IIn the summer of 1959 I constructed a 30 by 72 foot equipment shed for my brother-in–law who had a landscaping business. It is a pole building, and apparently some of the posts below ground level have rotted. My memory is that we used a post hole digger to dig the post holes. And then we poured a concrete pad at the bottom of the holes before we set the posts into the holes. Then I think we backfilled the holes by pouring concrete into the post holes up to the level of the surface of the ground.
Later I think i noticed that the concrete around some of the posts had cracked—presumably because of swelling of the treated posts. Presumably that moisture caused some of those posts to begin to rot over the decades since then.
Did those treated posts have inadequate treatment? I know there are grades of treatment some of which are adequate for placement below ground level. Perhaps the posts we got for that building were inadequately treated. Shouldn’t adequately treated posts be able to tolerate placement below ground surface? How does one prevent treated posts from swelling and causing the concrete poured in the hole around them to crack?
Thanks for any reflections you can provide.
Properly pressure preservative treated columns should outlast any of us. To avoid treated columns swelling and cracking encasement – use a bottom collar so top of concrete is roughly two feet below grade. Use higher strength concrete with at least four inches of premix between column edge and earth, or add rebar reinforcement to encasement surrounding column.
I understand the idea of a monolithic pour being best, but that may be difficult for a variety of reasons…. Instead I was thinking of pouring the 8=10 inch thick footings first, with the “collar” poured second after the poles are placed. I would reinforce the footings with a #4 rebar grid and was thinking of leaving rebar “loops” sticking out of the footing so as to tie the footing and collar together when the collar is poured over the top of the footing. I assume this will allow the footing to assist in providing uplift resistance along with the collar almost as good as a monolithic pour.
. Any thoughts on this approach? Thanks!
It will probably be just fine (you should have your building’s engineer verify) however it does sound like far more effort.
Just out of curiosity, what is the best way to suspend a 20 ft long pole weighing over 100 lbs 8-10 inches above the floor of an augered hole? Bracing at ground level and in three directions up high?
It can be done with one horizontal at grade and diagonals in direction of wall and to outside or inside – so three boards. https://www.hansenpolebuildings.com/2015/04/floating-poles/
we are in the process of building a pole barn house. The posts are treated and set into the ground. We have been getting some flack about the fact that we didn’t use concrete pillars. Should I be concerned that the building will only last 40 years? We want to make this our place for our retirement years. Also, it’s an investment to hand down to our children. We are in Montana where I realize there is an issue of frost heaves. Please advice me on the best type of foundation we can use for ultimate structure durability, Currently we are planning on a monolithic slab with in floor radiant heat. Also, is there a way to secure the posts to the slab to gain further strength in case of rot. Thank you
Here is the reality: https://www.hansenpolebuildings.com/2020/09/pressure-treated-post-frame-building-poles-rot/
As long as you properly prepare your site, have footings below front line and insulate your perimeter, frost heave should be a non-issue.
Planning to do a pole barn in Nebraska. Frost line at 42″, digging holes 52″ deep X 16″ diameter with 4″ tamped gravel at bottom. Then setting pole on this and filling around with gravel. Is this adequate to keep from settling or heaving, or should we pour a concrete footing for pole to sit on?
Unless your building has a very small clearspan, it is doubtful a 16″ diameter hole will provide adequate bearing surface for a poured concrete footing of at least six inches thickness. Ultimately you should rely upon the embedment design provided by the engineer who designed your building’s plans – otherwise you run a serious risk of settling.
After reading this article (https://customfenceorlando.com/concrete-and-fence-posts-florida/), I’m considering setting some 12ft 4x4s four feet down, resting on a ~5 inch gravel base…without concrete. I’d wrap the the post with “post-saver” sleeves and then backfill ~3ft with gravel and the rest with dirt.
This should be pretty stable for a fence/wall, but how would this work out for say, a 16×20 basic post-frame workshop?
Am I asking for big trouble down the road if I don’t set posts under load in concrete, even if they’re four feet down?
I live about 20 minutes north of Gainesville, FL. It’s feast or famine with rain around here. I’m either draining my pool because it’s about to overflow after several inches of rain in a few hours, or I’m filling it up because it hasn’t rained in weeks. Temps range from the 40s to the 90s in this area.
Also, these 4x4s I have are the standard ground-contact ones from HD…nothing special like UC4B.
Thanks in advance for any comments/guidance.
Without a concrete footing under the posts, you are asking for them to settle, and you should have a bottom collar (concrete poured up the sides of the posts 10″ or so above the footings) to resist uplift. 4x4s will be nowhere near sturdy enough to resist anything beyond a minimal wind load and anything treated to less than UC-4B requirements is likely to prematurely decay.
I am about to build a 30’4″ X46’4″ pole building for use as a shop-gargage with a 15’X30′ efficiency apartment. I have labor problems so I can only really count on myself but assume I can find another guy to help. The project is 90 miles from concrete plants.
I have 20 or so sturdi-wall wet concrete brackets. I intended to pour, meaning “have poured” a monolithic 6″ slab supported underneath the perimiter by a 15″ by 15″ “foundation-footing”. But I can’t get anyone to pour this and can’t do it by myself. Now winter’s coming.
Then I thought about just digging 24″ wide by 5’6″‘ deep holes (Montana) placing footings at the bottom and pouring concrete one by one from a mixer into each of a bunch of holes, with the top of the wet concrete on grade and at an elevation equal to the height of any future slab–if it ever gets poured later. I understand of course exactitude is necessary in placing the brackets.
I thought I could pour a 3″ slab 15’X30′ to support non-bearing walls and apartment floor. I came up with this thickness because I assumed I could do it myself or with one other man.
This would solve my labor problem, I thought. I could live with a hard gravel floor in the garage work area.
But then I realized I need a complete perimeter foundation because the building will have two garage doors (one 16′ wide) and a man door–all on one side of the building. I can’t imagine installing doors without a foundation to attach to underneath. I think I can manage the foundation and footing pour with two of us.
Question. Is the continuous foundation the only solution, or is there some way to build and install doors using only piers-and-brackets? Or is there some other way? Also, if I pour a foundation-on-footing, is a 12″ by 15’ inch footing placed a foot below the frost line (about 4 feet) about right? I would then pour a 12″ by 4 foot or 4.5 ‘ foundation on top of the continuous footing. I would give up digging and pouring the piers in this case.
I appreciate and read your articles, which are perfectly clear and knowledgable. Thank you.
Thank you for your kind words Mark, they are greatly appreciated.
You can pour piers only using wet set brackets and by using R-10 rigid insulation for a square form (with an insulated bottom) you can go to a 48″ depth. You do not need to have a concrete slab in place to set doors. They will get set 3-1/2″ above the bottom of your splash plank (even with top of an eventual nominal 4″ (actual 3-1/2″) concrete floor (don’t do only 3″). Eventually you (or someone) will want a concrete floor in the garage work area.
I am having a 40x60x14 pole barn with 10′ sheds on both 60′ sides built and had a friend level the pad. The specs from the builder required =/- 3″, but I checked the level and have as much as 6″ difference. I had already intended to order 15 tons more gravel than required for future use on my driveway. Could I use the additional gravel to compensate for the difference, or should I get it re-leveled? The pad did not settle, we just didn’t read the elevation pole correctly (inches vs 10th of foot with “is it in centimeters thrown in for good measure)
You should reach out to your builder, personally I would have been happy building on a site with only six inches of grade change.
Here are some things for thought. I will be referencing the 2021 International Residential Code (iccsafe.org). Naturally we want to calculate/design from the roof down on a single story structure Multi story building first start from the top so that weight (dead load, live load, snow load) can be added to the top of the story below, etc. Lets take a 30 foot wide building with posts spaced 8 foot on center, the length doesn’t much matter for this part. We have to calculate the “tributary width” of the roof load on each post. The width is 30 feet but is supported by 2 posts (one on each side of the truss), so use 15 feet. We are going to assume that each post is carrying one half the load and the adjacent post is carrying one half. Midspan of post to opposite post equals 8 feet (the same as the post spacing). Lets ignore dead and live loads for now, we’ll use 50 pounds/ft. sq. as snow load (upstate NY). 15 x 8 x 50 = 6,000 pounds. Each post should be designed to support 6,000 pounds (about the weight of your truck). The ground must be capable of resisting this load. Using Table 401.1.1, lets assume the load bearing pressure of the soil is 2,000 psf. 2,000 psf = 13.9 psi. A 6 x 6 (actual) is 30.25 sq in. 13.9 psi x 30.25 sq in = 420 pounds, not nearly capable of resisting our 6,000 pound load. I see the term “collar” in some of these discussions, it’s a footing, the footing, normally made of concrete is used to spread the load from the smaller foundation/framing members to a larger “footprint” capable of matching the soil load characteristics. In our case we would need a 24 inch diameter to support the post load. Area = pie R squared = 3.14 x 12 inches squared = 452 square inches…. 13.9 psi 452 sq in = 6,283 pounds. OK, exceeds the calculated 6,000 pound load. The thickness of the footing is another matter. It depends on what steel reinforcement is used (rebar), a grid of #4 (1/2″) spaced 6 inches on center each direction will be more than adequate. The location of the rebar grid in the height of the concrete gets complicated but placing it half way will work fine for this application. Be sure to remove loose soil from the hole and use a hand tamper to pound the hell out of the base. At that point you can set whatever pole design you choose on top of the footing. The height of the footing should be your frost depth so when water gets between the post and footing it doesn’t heave the post up when it freezes.
Other than ignoring dead loads (as well as any overhang) I would be generally in agreement.
I built a building to l without footings, the county says it really needs them. What do you recommend doing to add them to an existing building? I have 6×6 posts 48″ deep
Your county is absolutely correct. Your best solution is going to be to hire an Registered Professional Engineer to do an analysis of your overall situation and design the least intrusive possible repair for your particular case. You might have to temporarily support each column so you can excavate below it and pour a concrete footing, then somehow try to properly compact around it – in simple words, you have a lot of work ahead of you.
I am scrambling a bit for information here as our plans recently changed and I need some advice. As a local business owner I must apologize for not using your company but was trying to do as much business with local people, especially those who support my business.
We are building a 36 x 88 x 16 foot tall wood frame structure to store our boat, etc. We had planned on a pole in the ground construction with a 6″ concrete floor after the structure was built. However, the contractor ran into some various old lines, etc when drilling the holes. He suggested we change course and pour a 12″ by 12″ footing, pour the slab, then attach the building to the concrete. Is this okay and will it withstand as much wind force as having the poles in the ground? Also, we are considering changing the building to 18′ tall sides, will the new construction concept, if carried our correctly, work for a side that tall in Wyoming? Is there anything with frost line, etc we need to be worried about? I think wind is my biggest worry, although there may be things such as settling I am underestimating.
I would appreciate a professional second opinion as this is a once in a lifetime purchase and I want to support our local trade but value further opinion.
Any building of this magnitude built without fully engineered, site specific plans is at risk. Given your concerns about wind design and lack of depth to prevent frost heaves, I find the 12″ x 12″ footing suggestion to be highly questionable. Embedded columns are going to be a far stronger design solution and (in combination with your concrete slab on grade) can reduce shear forces imparted into your building shell by as much as 25%.
Im building a camp using telphone poles i have 7ft of pole sticking out ground I dug holes 3ft deep and roughly 18-20” in diameter and set with 3- 80lb bags of sacrete per hole. Is this going to be sufficient enough to support the structure which is 30ft by 40ft
Whether this may or may not be adequate should be determined by the engineer who produced your site specific plans. Factors involved include column spacing, soil bearing capacity, design wind speed and exposure, roof loads, roof slope and whether building has enough siding to properly transfer wind shear loads from roof to ground.
I’m going to have a 40 X 48 shop built. It’s in a county with very few written building codes. But I’ve spent 8 years working with designing trusses, conferring with building inspectors and engineers in another state. I want my building constructed correctly. My building will have 12 ft walls and attic room trusses with an 8/12 pitch designed for 30 lbs L.F. on bottom chord and a 20 lb per S.F. snow load on the top chord. There will be a center load bearing wall with a thicker footing under the floor. I want footings 24″ diameter 24″ below frost line. But I also want post frame construction. I’m thinking aboutl having a 5′ wide perimeter dug out 36″ deep. Then having 18″ diameter holes spaced 8′ o.c. an dug below the 36″ deep perimeter. Then frame up the footings 24″ diameter to include the post holes. Then have the correct treated poles set and braced and pour the footings and post hole concrete in one pour. 3/8 Rebar would be ran through the footings. An 8″ wide concrete stem-wall would be poured on top of the footing to 12″ above grade that would include a 6″ gravel floor base, 2″ insulation on the inside of the footing and stem wall and on top of the gravel floor base, then a minimum 6″ concrete slab with additional 38 rebar. The floor would include in-floor tubing for heating.
Sounds like you are going through some extra (and expensive) efforts. There really is no structural reason to add a concrete footing and stem wall between columns. 24″ diameter footings are probabl;y inadequate to support the imposed loads.
Hello, I am looking into a garage for my property. I decided to build my own after seeing the market and knowing I can get more features added with my own two hands for less. I am thinking of a 24x24x9 structure. I live in rural NY and know I will need a permit for my area. I was thinking of placing a 25×24 concrete slab but then I was told concrete footing would be a better/cheaper route. If I add the footings, would adding a concrete slab later be easy or practical? Or would a wood floor work either way if foots are placed? Also, does the kits come with information that can be provided to the building department? I think the town would have their engineer come out and look at the area in question.
Side note: We are on a hill so we were able to get a landscaper to raise the ground by 10ft to level the section that the garage would be placed, so it’s been a project in the making.
Please reach out to your Hansen Pole Buildings Designer Carson Monday morning at 1.866.200.9657 Thank you.