Question about support posts for raised wood floor in shop

[Logan William]

So last year I bought my house and it came with a 40 x 60 pole barn style building, only problem was I bought it with the shop as is....aka full of crap! Over the past year while taking a break from the other projects I've slowly been able to work on cleaning it out and have finally started to get down to the dirt floor and am able to start looking at what the next step is for starting to make this building more usable.

Now due to everything else I want to do to the house over the next year or two I can't really afford to drop the 4-5k it will take to put in a concrete slab for a portion of the building, so I'm strongly considering putting in a hanging/raised wood floor, similar to deck construction. This gives me the extra storage/work area now for around $300 bucks plus flooring and labor(which is free of course), and I'm fortunate enough to have lots of building so that when I get heavy enough equipment I still have plenty of room to pour a concrete pad next to it and have my choice of do I stand on wood or concrete today.

I'm planning on 15' long 2x8's doubled up for beams supported on the ends and center of span on roughly 115" centers to hang the joists on, 2x8 joists on 12" centers then put 2 runs of some type of T&G flooring, with the top run set at 90 degrees to the first. Right now I'm planning on putting in a 15' deep by 20' wide area which gives me plenty of room to store stuff off the ground(lumber), give me some extra working room and provide a base to eventually build the walls on. Assuming the joists are all grade 2 or better southern pine it gives me a 100 PSF live load rating which should be more then sufficient for what I do.

My question is I'm planning on anchoring the 2x8 beams to the 6x6 building poles where I can, but I will need to dig 4 footings/pilings for the center and end of span supports for 2 of the beams. From doing some very rough guesses the bottom of my beams will only be about 4-6" above current grade level of the floor so I'm unsure about how to support the beams. Local frost line is in that 42" down range, so I'm debating about digging a 8-10" dia hole 42 to 46" and bringing it up to the approriate height and putting the post anchor right on top of it and setting the beam directly on the piling, but that doesn't allow any wiggle room for leveling the beam. I've also considered that since it is inside and moisture should be at a minimum that I could anchor the post 10-12" below grade level, backfilling with gravel/dirt then I have more wiggle room for getting the beam level.

Any suggestions on how you would do the 4 post supports, concrete all they way up or only part of the way and put in a longer post, or some other option that I didn't mention? I'd love any additional feedback on other aspects that as well. I've attached a screenshot of the AutoCAD layout, its still a work in progress but should at least help convey the intent and give me a better chance of cutting pieces to the correct length!

[David Gutierrez]

just a couple of thing to think about. Doubled 2x8 for the beams feels a bit light. You should check the beam size or have someone check it for you. attaching the floor to the pole barn posts may not be a good idea as the post were not intended to support the floor load and roof load. not sure what type of footing is under the posts but the footing could be the limiting factor.
With a 9' x 9' area supported on concrete pier the total load at 110 psf ( 100 live + 10 dead) will be 8100 pounds. On a 10" diameter pier the load is coming down on 1/2 a square foot or about 16000 psf bearing at full load. Around here we would be using 3000 psf for footings.

as to your last question set up sono tubes and level them. then place the beams directly on them and shim the beams level.

[Thom Sturgill]

I agree with David. I would probably go up one in size and triple rather than double on the beams. Another option I have seen is 2x12s bolted either side of the vertical and the joists supported on both.

[Bob Riefer]

Since you're planning on putting in a concrete floor when budget allows in the future, you might consider making this a temporary structure by building a free standing platform on concrete pre-formed piers. If you used screws to put the platform together, you'd be able to disassemble later to reuse the lumber.

[Logan William]

just a couple of thing to think about. Doubled 2x8 for the beams feels a bit light. You should check the beam size or have someone check it for you

Once I get the updated layout based on the comments below I'll pull my timbers book back out and rerun the numbers, I had some questions about it to when it came out to 2x8's the first time but I'll double check with new loading layout

With a 9' x 9' area supported on concrete pier the total load at 110 psf ( 100 live + 10 dead) will be 8100 pounds. On a 10" diameter pier the load is coming down on 1/2 a square foot or about 16000 psf bearing at full load. Around here we would be using 3000 psf for footings.

And this is why I post and lurk here! I didn't even think about the pole barn footings, based on similar construction buildings in the area and other buildings on the property I'm guessing that they dug the hole and placed the pole in a bed of gravel then backfilled, I highly doubt they sunk them in concrete. I'm working on redoing the layout to put the beams all on concrete piers and then figure the new tributary loads off the new pier layouts to get a better idea of how large of a footing it will need.

I agree with David. I would probably go up one in size and triple rather than double on the beams. Another option I have seen is 2x12s bolted either side of the vertical and the joists supported on both.

Triple may be an option, but I'm personally not a fan of sandwhich bolting unless you use large enough posts to notch as well. Otherwise you're relying on the lags/thru bolts to transfer the loading to the posts, if you upsize the posts and get 8x8 and notch both sides you're now in compressive strength of the posts and using hardware to just keep it in place.

Since you're planning on putting in a concrete floor when budget allows in the future, you might consider making this a temporary structure by building a free standing platform on concrete pre-formed piers. If you used screws to put the platform together, you'd be able to disassemble later to reuse the lumber.

Whenever funding allows the slab I'll probably put it in and keep the wood floor and have both, one of the luxuries of having lots of space! When they built the building they at least planned for making a slab easy to pour as they ran 2 courses of 2x6's or 8's(haven't measured yet) around the outside with the bottom one designed to be the slab height. On this floor I'm using the joint between the runs to serve as my floor height reference so whenever I put in a slab I can have the 2 surfaces on the same plane....hopefully.