Is Renovating a Pole Barn Practical?

Welcome to our newest feature: 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 segment. 

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

Dear Pole Barn Guru:

I am an architect in NY state and my client approached me about a year ago to renovate his existing agricultural use pole barn into an accessory use private art studio with about 8 studios on the first floor and two sleeping quarters on the second floor.

He’s on a tight budget and has been very careful regarding interviewing rough carpenters and concrete contractors as we gear up to submit for plan review to the town.

One question that has us stumped is whether we need to put additional foundation work into the building.  The barn is probably from the 60s-70s and the wood looks pressure treated however we don’t know with what.  We haven’t dug any test pits under the poles to see how deep they go or if there is any rot but visually, the posts at grade look pretty solid with no depletion of material and some mildew staining, maybe mineral deposits from wicking up of water.  Again not sure.

The client has had a concrete contractor come out and between the two of them and the framer they wanted to put in new columns and new posts adjacent to the old ones.  However, they were not clear as to why they wanted to do that.  They discussed putting in concrete poles with Simpson type connectors and pinning the columns to the piers.  I started to try to talk them out of this explaining that the building type is based on using the buried portion of the columns to resist bending and it provided great lateral resistance against wind.  I am not convinced that any of them knew why they were trying to do this other than some false peace of mind for some reason.  The existing 4 X 4 posts are about 4 feet on center apart along the exterior walls and within the barn so there is a forest of structure.  The barn shows no swaying or destabilized areas.

As the contractor in his fee gave the client an allowance for 30 posts.  I told him it was unclear where we would put them and I wasn’t convince that we even needs new posts, or concrete foundations for that matter.  I am pushing really hard to not pour any new foundations.

Anyway, here we are a week to submitting the drawings and the set is not clear as to whether we are going to do this or not.  The intention for a floor is to pour a 6″ concrete slab over a vapor barrier and 6″ of granular fill on compacted soil.  I thought it would be fine to leave the posts as they are, pour a haunched slab edge along the perimeter of the building and go with that and just pour right around the wood columns.  The perimeter columns would be surrounded on 3 sides as the screed would be nailed right up against the face of the exterior posts (in line with the rear face of the existing board and batten siding.

The client is still on the fence and somewhat convinced we may need dig down to put in new poured concrete piers encasing the existing columns at the exterior walls.  I figure the barn has stood up for this long, and has had no settlement issues or problems distributing its loads to the ground so why would pouring a new slab impart any significant additional loads or even the new art studio occupancies or sleeping quarters above which would not be so high make those loads any worse?

I guess the question is, to convert a pole barn from a previous agricultural use to a more accessory private use, why would we have to pour new footings in the ground?  Do I have to consider any special conditions when thinking about pouring a slab or can I just nail a screed board around the perimeter of the building and just pour up to the top of it and call it a day with no additional foundation work.

I hope there is enough, but not too much information here to give you an idea of what we are dealing with and get some feedback as you really seem to know what you are doing with these buildings.

I’ve attached some drawings so you can see what we have going on.

DESIGNING IN NEW YORK

DEAR DESIGNING ~

My first opinion (without obviously having seen the existing building, or photos of it) would have been to have knocked it down and started from scratch. When all is said and done, it probably would have been far less expensive than all of the remodel work involved in renovating a pole barn.  As humans, we get very easily caught up into “not tearing something down”, when sometimes, it is the best answer.

Right now, we are quite a ways down the pike, money has been spent and we’ll all get on the same page with where to go from here with the existing building.

From your standpoint, it would be beneficial to excavate at least one existing column to confirm the columns extend into the ground below the frost line, and to make sure the concrete footings are adequate in diameter to carry the weight of the structure above. These would be the issues which would be most prone to cause potential problems, and both of which you want to write around to protect yourself from possible liabilities.

Unless the columns are showing signs of decay (which would be rot between an area a few inches above grade, to 8″ below grade) there would be no reason to replace them, unless they are inadequate in size to be able to carry the imposed loads.

Simpson brackets are not designed to withstand moment loads. There is one wet set bracket which is available and is designed for moment forces, but I am not seeing this as a practical solution, unless it is just one of resolving fear factor.

My professional opinion going forward (assuming column depth and footing diameter are adequate) – install a pressure preservative treated 2×8 splash plank around the building perimeter, with the bottom at grade (0 point). Where interior slabs will be poured, excavate down six inches, place four inches of clean compacted fill, and lay an insulated vapor barrier (such as double cell reflective insulation) then place two inches of clean sand over it. This will put top of fill at grade. Install 1/2″ rebar “hairpins” through each of the perimeter columns. These should be a minimum of five feet long (I can supply further details if you or your client opt for this). The hairpins will tie the columns into the slab. Unless someone plans on driving tanks or D-9s in the building, there is no reason for a slab to be over a nominal four inch thickness.

One thing I have learned over the years – if you can find a way to give a customer peace of mind while still following solid structural practices – you have it made. Renovating a pole barn is a challenge, but may be a worthwhile one at that.  Good Luck and let me know how it all turns out.