Slab install question

[Kangaroo ID]

My 40x48 pole building was recently finished, now im prepping for the slab. I will be pouring it my self with the help of a couple helpers. My question is what to do with the finished height of the slab. The building has commercial girts, they lay flat between the posts. The lowest girt is a treated 2x6 with another 2x6 as the skirt board just inside of the siding but still between the posts. It seems that if the slab is poured tightly up against the bottom of the first girt it could try to lift the entire structure if the slab heaves in the winter, (N. Idaho gets a decent amount of cold) maybe I am over thinking it and an interior slab wont lift like that? Or should i hold the slab down an inch or two from the bottom of the girt board to give thing some room to move

 

[73RR]

If frost heave is a concern them separate the slab from the walls with ½" foam board.

 

[wssix99]

Or should i hold the slab down an inch or two from the bottom of the girt board to give thing some room to move

Concrete shrinks, so it should pull away from the girts as it cures and give you gap after the first month of cure.

The width of that gap will be (slightly) different on different walls and will be more or less depending on the characteristics of the concrete and slab.

As the slab shrinks, you don't want the concrete "grabbing" on to the girts and pulling them inward, so your contractors should be able to apply a release agent (like oil) to the boards to keep the concrete from adhering during the pour.

If you'd like a little extra room, you can add some expansion joint or foam to the boards.

 

[Kangaroo ID]

My concern is that the slab would be under the girt, since it is commercial girting they are installed flat like a bookshelf between the posts. Foam would have to be nearly 5 inches thick to fill the gap from the skirt board to inside of the girt

 

[GMCGarage]

Make sure you are away from the girt. You dont want direct contact. leave a gap and caulk it. Also what are you going to do at the columns?

 

[73RR]

My concern is that the slab would be under the girt, since it is commercial girting they are installed flat like a bookshelf between the posts. Foam would have to be nearly 5 inches thick to fill the gap from the skirt board to inside of the girt

Run the foam (or just about anything not attached to the structure) vertically, at the inside face of the columns so that the concrete has a place to slip/slide.
Yes, you will need to have the area behind the 'foam' backfilled. Depending on what you decide to use, it could be used as a visual guide for top of slab.

 

[Hot Rod Grampa]

I know this is GJ but that is bunch of concrete. At 6" thick that's 35 yards. Are you doing this in sections or in one big pour? What are you using as height reference around the perimeter? Will you be using any power tools for screeding or trowling or polishing? Are you using mesh in the floor on stands or pulling it up as you go? Diamond cutting after the pour or just letting it go? Vapor barrier under the pour or on top of fill? I hope it works out for you. Just don't let the driver water down the mix to make it easier to push around. Could be a permanent mistake. Good luck.

 

[wssix99]

My concern is that the slab would be under the girt, since it is commercial girting they are installed flat like a bookshelf between the posts. Foam would have to be nearly 5 inches thick to fill the gap from the skirt board to inside of the girt

Ah - We had another member who is doing a heated floor and they didn't want that space filled for heat/loss issues. So, one of the solutions was to put up vertical skirting in between the posts to act as a form and then go back and fill the voids between the skirts with insulation.