Moon,
As part of putting mine up, I put a treated 2x6 along the very bottom, on the outer side of my main support as a footer, for 2 reasons. First, I used it to nail the metal for the sides and ends to it, but I knew I wanted to concrete the floor inside, so I figured it would also serve as a permanent form for the concrete floor too. Basically then, I just formed out the areas for the large doors at each end of my barn, with the doors wide open, used my FEL and then put about a 2 inch layer of sand down over the entire area first. Oh yeah, and I stopped by our local "illegal worker" pickup point, and hired about 3 of them that had done concrete work before.
Remember, I'm in Texas and when I did mine in August, you don't have a lot of time to play with wet concrete before it becomes "set" concrete in our heat.
Then I bought some of those little plastic do dads that hold up either rebarb or another type of metal reenforcement that you want to put into the wet concrete to strengthen it, and laid that out in one half of my barn. In my case, I used the roll out kind of metal concrete reenforcement.
I had rented the necessary concrete working tools I needed, ( all basically hand tools and no power tools) and bought several pairs of rubber boots. After that, it was just having the concrete truck bring it out here, putting that shoot into one end of the barn and swinging it slowly from side to side to disperse the wet concrete as evenly as possible, and then spreading it out over the entire area evenly while wet. I put my concrete at 4 inches thick.
I repeated that about a month later for the back half of the barn floor too. I split it up because of the heat, affecting both the concrete and me badly in August.
While the concrete is still real wet, since yours is 28 ft wide, like I did, you may want to lay in those expansion strips too, at the midway, width wise, point. Also, don't forget to consider that you'll probably want to wash your concrete floor someday in the future too, so slope it slightly downwards at each end, only in front of your door area, starting about 8 feet from the doors at each end.
We worked it to even it out, and then with the "jitterbug" to get the bubbles et al out, and the stones from the top. We then worked at smoothing off the top.
It cost me wages for the 3 men at $8.00 per hour each, for 6 hours, plus hamburgers and a soda pop for them for lunch. That was about $166.00
Rental of those tools was inexpensive, but I don't recall how much exactly. I think about $50.00. The rubber boots I bought, I'm still using for other things now.
The concrete cost me $1100.00 per half garage, delivered.
All together, I believe I figured it cost me about $2700.00 for the whole deal, (both halves). That was a whole lot better than those bids of $6000.00 and up I got from a couple of contractors.
