shop concrete floor thickness

[Innovate1]

Building a 30 x 40 for vehicle parking on one side (camper or medium size RV) and some shop stuff in the rest. Standard concrete floor seems to be 4" with wire mesh. Don't expect to have anything too big. Perhaps a bridgeport mill or similar size will be about it. Vehicles will probably be heavier. Should I go with a thicker floor?

 

[JohnnyK8]

Ask for 4" and you'll get 3.5".

Planning on getting a hoist? If you stay on garage journal you will be [emoji3]

I'd go for 6". Just my opinion.

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[JoeMcGov]

Properly prepared and/or compacted subgrade (dirt/gravel under the concrete) is as important as concrete thickness.

4" actual thickness would be the minimum thickness. Add in a fiber mesh type of reinforcement and properly prepared subgrade and you're golden.

 

[346ci]

I went with 4", added some extra where the lift posts would be. Unless you are getting a 12k+ 2 post lift, 4" is fine.

 

[JohnnyK8]

Agree 4" is all you need as long as you get 4"

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[BillK]

I dont know what concrete is going for now days but when I built my 24x24 I asked for 6 inches. It only added a couple of hundred dollars at the time. If I am doing the math right you will need about 5 extra yards if you do 6" compared to 4" For me it would be a no brainer especially if you plan on parking an RV on it.

Plus with 6" if you decide to add a lift in the future you will be able to do so without worrying.

 

[bad_idea]

I had my 30x40 slab poured in April. To upgrade from 4" to 6" was an extra $1100 or so. I stepped it up to 6" to accommodate a lift down the road a bit. If you NEVER plan on a lift, then stick with the 4".

 

[MushCreek]

When I had my machine shop, it was in a rental warehouse that had 4" (3-1/2", actual) floors. They were never intended for a machine shop. I brought in an 11,000 lb. CNC machine that sat on four 4" round pads. Never cracked, never moved. The machine was still dead level after 5 years. I drilled holes for anchors in that floor, so I know how thin it was. That being said, when I built my shop here, I went 6", in case I ever want to put in a lift.

 

[ConCretin]

I agree with most of the prior comments. With a properly constructed base, a 4" slab is more than adequate for your intended use. With that said, an extra inch of concrete is relatively inexpensive, increases the strength of the floor and allows for tolerances in grading.

You can read my Guide to Floor Slabs below for some additional thoughts on your project.

 

[hake]

I have 7” in my shop but it was due to a mistake. I was shooting for 5.5”.


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[tapout187]

I just had my floor done in my 36x46 pole barn back in August. The contractor needed to bring in about 25 tons of 3/4 blue stone to get floor elevation up and he poured 4000k psi fiber mesh at 5 inches thick. He did two 4’x4’ areas like 10-12 thick where the lift is going. He leveled and compacted the base. He power trowel finished and saw cut the final. It was I thinkn31 yards of concrete and cost $9000. He did a great job. He did 5” thick and he said that would be more than good and anything more would drive up the price and be wasteful.

 

[Randy in Maine]

Mine is 6" thick (8" under the lift area) and I used 4,000 PSI concrete with mesh.

 

[seanc_mt]

Went with 5" + fiber mesh + #4 rebar on 2' centers. with the absolute best base we could put down.

Why skimp out on the one thing that is pretty much 100% going to support your entire building and really really hard to fix after its done...

 

[SkeeterZX200]

I went with a 6" pour. It was only about $2500 upcharge from 4". This was on 1800 sq ft.

 

[matt_i]

I went with 6" (the elevations are my own measurements from rotary laser level), 4ksi fiber with actual rebar in it. 6" deep base of 3/4" nominal washed, crushed limestone, also plate compacted.

My plans are for filling it mostly with heavy machine shop machinery and rigging those with a forklift (which is also a very heavy machine just by itself). So far I've been to 50% of intended max but we await me finishing up the insulation and drywall before full move-in can be completed.

If I had none of this, a 4" minimum slab would be just fine. If you're worried about the anchor bolts one could use (omg not mfg spec'd ) epoxied anchors or thicken the slab in the general area where a 2 poster could go.

 

[maxpat82]

Mine is 5" with 3'x3'x12" for the lift pad. 32KPA(~4600psi)
all fibermesh...no steel.

 

[lakelandcat]

Better to have it and not need it than to need it and not have it.

 

[kbs2244]

I don't personally do concrete.
But I have outsourced enough to learn:

If you have a choice between fiber and steel, go steel.
It has history and logic behind it.