A 40' wide barn with 14' high ceilings can have stairs on the back 40' wall to the attic.

The trick is to have the right trusses. Bonus room trusses would be the way to go but that was more money I just made sure I could stand in the center and had about 4' walk way... to do that the bottom truss board has to be 6" or 8"...

Then a 2x12 board, really long, on the back wall at 45* (degree) nailed into the poles... thats your first stairs stringer. (that great big framers square comes in handy.)

The last bay of trusses where the floor would be is not sheeted and the stairs come up through that bay. This gives you about 3' of room at the bottom to have a door.

The trick is to get that first board set, its pair board just matches it and fastens to the truss.

Cut 2x4 nailers on those boards and then lay down two 2x6 treads...

Now that gives you a runway down the middle of your trusses with heavy duty stairs getting to them, add a rail.

You will walk up through where the floor would be and step over to the attic floor.

Then on the outside of the runway I just added nailers down through all the trusses and added 4x8 sheets of plywood all the way down through there for shelving.

So now you got a runway with shelves on both sides... I left a few bays without shelves and added a closet bar... thats where all my hunting gear hangs.

You run out of room fast.

I came up with all of that and I think the barn place started selling it as a package.

looks really nice and a smart use of space. I was considering trustees that give open space but have not priced anything yet. Also thought about the room stairs take up and thought about stairs in the outside to get in the loft to not take up the room inside. That may make Turing the upstairs into an apartment if there was room later easier.
I need to talk to builders and get pricing nailed down. Need to take my wife visiting newborn buildings to figure out size but she is very challenging visualizing space needs. I asked her once how large a space she needed for the kitchen she could give classes in and she said something so small the stoves would not fit with room to open them. And like you know they fill up fast when putting in shelving and such.

I built a barn... put my stuff in it... and needed another barn. Don't go small.

If I had a second building say with gravel for cold storage of things it wouldn't take up so much room in my nice barn... camper, tractor, boat... so theres that too.

My problem is once I get started with add on's a 50k barn will be 150k. Radiant heat floor larger size extra insulation, electric bonus room trusses, plumbing ect. septic Then I won't build anything and put it off for another 10 years. That's what got me thinking about building small just big enough to meet the wife's needs for classes and large enough to turn into another rental house if plans change in the future. But also with organized plans in place to have a visually appealing expansion if thing go as well as hoped for in the future.

The lower cost I may actually get it done and moving forward not just keep spinning circles.

I dont want to finance anything also is not helping. But if I do I dont want to go moer than 50k preferably around 30 so need a good chunk to put down.

Sometimes I over think things to much anf never get started other times I look back and wish I had planed thing out better.

For floor heat id just run loops of pex all through the concrete. Have them go in and come iut where youll put an outside boiler in the future.

I think i read it need to insulate under the concrete to keep the cold from the ground asorbing the heat? also avoid the pex where future walls may go to avoid poking a hole in it when securing the walls. Also seems like I read( its been years) Ther should be an extra loop in front of doors and windows.

But thats all from memory going back years when I start planing but prices stop me from moving forward.

I could see laying foam barrier down… im not sure id do all that for a barn like im talking. I mean a 3” tapcon would mean not to have any pex in the top two inches which i wouldnt think youd want close to the surface at all. Id run multiple loops with multiple in and outlets. Any loop can fail then. As far as insulation itd prob just be that thin foam stufff to roll out, lay pipe on, pin tubing around, add at least 10 3” elbows through the forms, a couple drums, heck i might even leave 2’ at one wall just gravel,.pour 4” on top, and i cut my concrete every 8’.

I try not to over complicate things. Good luck. Im about idead out on this one.