How thick to make concrete floor??

[Matthew Curtis]

I am building new shop. How thick should the concrete floor be in central Ohio??

[Joe Watson]

Your best bet would be to ask the local building inspectors office.

[Chris Damm]

Not less than 4". Most contractors will pour it 3.5" but 4" will hold up better.

[Dave Wagner]

Yes, check your local building codes, is it a slab on grade or a concrete wall/foundation and you are just pouring the middle?.

Different ways of doing it and may have different requirements. Most should be at least 4" min.

My slab on grade garage had to be 12" thick around the outside, 12" in from all sides and 4-5" in the middle for my garage, and have a certified drawing from a PE (Professional Engineer).

[Donny Lawson]

I would go with at least a 4" slab with fiber. When you have the slab poured add the lag bolts to the concrete so you can tie down the walls with them. Mine was done that way a few weeks ago and it's looking great so far.
Donny

[Bryan Rocker]

At least 3 1/2 inches, I have poured several drive ways for HFH here in Greene county and they are 3 1/2 inches....Due to the number of very cracked and moving floors I would go deeper and I plan to. When I build my shop I plan on adding several additional piers across the interior portion of the slab to stabilize it.......

[David Roberts,Fitchburg,Ma]

I have a 4" slab in my 24x 40' pole barn/shop, added after the roof and walls up were up. My floor is protected from the weather, and has only minor cracks after 5 years, no lifting. There is several things I would do different if I ever did this again. First 4" of high R insulation board underneath, my shop is not heated all winter long, only weekends when I work in there, and the floor sure is cold. Also, I wish I had put radiant piping in, even if I didn't plan on buying the heater, you can't really add piping afterwards. New solar vacuum tubes could become affordable enough to use the slab as a heat sink, or use an outdoor woodstove set up for hot water.
I also asked my concrete guy about stength and fiberglass, he suggested if you are going with a smooth floor, and will have cars in your shop, you won't like the threads poking into you while you are laying down.

[Herbert Mulqueen]

I have built way over a 100 post frame buildings okay hundreds.

From garages to saw mill planer buildings to truck depots.

My floors at outbuildings at my house are the following:

Ramps -----11.25 inches thick -----front of apron to floor
2 levels(rows) of rebar 5/8 thick on chairs.
5000 psi concrete with micro mesh

Why so thick?

The moment of impact is the ramp not the floor. Just like an airport runway----the Numbers are very thick and the rest of the runway is pretty thin. An airport runway is like a ribbon and wants to move, thus thick numbers.

Why not 3000 psi mix?--I always did 5000 psi concrete. However if you check the concrete company--it usually is a small upgrade to get concrete a whole lot stronger. So why not.

Floors--------5 1/2 inch thick with 5000 psi concrete with micro fiber.

Machinery placement----usually----this is very subjective---I know this is a woodworking site---but any impact machinery---like an iron worker needs it's own foundation and we would form this separately than the floor.

I had a drill press that weighted 38,500 pounds and that had a 12 inch floor separated from the concrete floor.

Just remember impact and vibration.

Insulation----we put 1/12 to 2 inch blue foam around the perimeter. That means you have 48 inches around the whole perimeter.

Why the insulation?

When the cold slab hit the warm air in the heated shop you get drafts and lots of humidity. The floor insulation truly make the building feel a lot better.

Remember to pre-install some underground elbows for " Stuff ".

Such as electrical, plumbing , put them on a few corners or sides, where you see fit.

A layer of gravel/stone compacted is also a very good idea. You can rent a hand vibrator and you can do a small building in an afternoon.

Very smooth machine finish on the floor, rough broom finish on ramps.

Why the 5 1/2 inch and 11.25 inch thickness?

It is the size of a 2x6 and a 2x12.

Free advice is worth what you pay for it.

Good luck.

Herb

[Herbert Mulqueen]

Insulation----I live in very mild rural eastern Virginia. 2 inches of foam is really all we need.

If I lived in the cold of Minnesota, Michigan, Maine, and other brisk places I would use a minimum of 4 inches of foam insulation.

Saw joints----make sure your finisher cut the slab within 24 hours after finishing. Cut a few more than minimum. There is a charge per foot. Weight the cost of having another row of saw cuts.

I used the Rust-O-lem SP? ----garage floor paint----it has worked well for me. Do it before you put anything on the floor.It goes on fast and a little masking tape at the ramp ---makes it look like a professional job.

Sorry for the addition.

Herb

[John Coloccia]

It needs to be thick enough to reach the ground. Glad I could help.

:p

[Scott T Smith]

Matthew, if you're not going to be putting extremely heavy equipment inside your shop, a 4" slab should be fine. Be sure to install a heavy vapor barrier underneath it.

Insulation is a great idea, as is tubing for radiant heating.

Try to find a concrete contractor that really knows what they are doing, as this is not an area where you want to skimp. So many concrete installers today are not concerned with how the slab stays together long term, and so they add a lot of water at the site in order to make the concrete easier to work, and they will puncture the vapor barrier in order to decrease the time delay from pouring to final finishing. Neither one of these is beneficial to long term slab quality.

I prefer at least a 4000 psi mix for my slabs (and usually go 4500), with a low slump on site (3.5" - 4.5" max). I do not allow water to be added on site either (but will allow admixtures for pumping), and all concrete must be placed in less than 1.5 hours from the initial mixing.

In '08 I poured a 150 yard slab for my current shop, and today there are ZERO cracks other than at the end of a saw cut expansion joint. It was a 6" slab with 12" ramps, and 12 x 24" footers with radiant heating and insulation. The footers had multiple layers of rebar (as did the heavy machine areas), the rest of the slab had 6 guage heavy reinforcing mats on 2" chairs.

You also need to make sure that your grading contractor removes all topsoil and biodegradeable materials from underneath your slab (such as roots), and compacts all backfill extraordinarily well.

Since you live in a cold area, you might want to consider adding insulation around the perimeter of your slab - especially if you use radiant heating.

Good luck with your project!