I am planning on putting the floor in my shop soon.

I will someday hopfully have a aboveground hoist, but other than that I will be just working on cars and light trucks.

How thick should i make the concrete?? AT 4" I will need 45 yds, and at 6" it will be 65 yds. So it will be quite a lot more.

Also how much does concrete usually cost per yard???

Thanks in advance.

i worked construction around christmas and we layed out a floor for the concrete guys. the garage was planned to have a lift in the back. when the guys were done smoothing out the floor it looked like the concrete was over 6" thick where the lift was supposed to go. the whole floor wasnt that deep though, we just dug a whole in the area the lift was planned to go. there was also extra rebar reinforcing in the hole.

3.5 to 4 " will be fine, but i would put the rebar[3/8"] on 16 to 18" centers. the last time i priced some concrete it was in the 65 to 70 dollar a yard range here in texas. mike

I poured mine 2 weeks ago, 4" thick with a 8"x8" footer (trench) all the way around. I used 3/8 rebar in the footer, the first about 2" from bottom, and the second about 5" from bottom. More rebar running about 4" away from the inside of the footer, and concrete wire for the center.

If you need 45 yards at 4" thick that must be a big ass shop. Mine is 45'x22' at 4" thick, 8"thick footers and a 4"thick 12'x10' approach apron and I only needed 16 yards.

I'm in construction and have built a few shops for myself besides the commercial work we do. Personally if I was building something that I might stay in for years I'd go 6". The reason isn't necessarily the weight of whatever your working on as much as how much you might point load the floor. By this I mean large amounts of weight concentrated in one place. (Jacks, Jack stands etc.) If that's not a concern to you then 4" would be adequate. Around here concrete is 70-75 dollars by the time you pay their truck rent on top of the cubic yard price.

4" on a well compacted base should be plenty. Commercial heavy equiptment floors are 6". I'd use 6X6 10 ga. welded wire mesh for the reinforcement, rebar gets expensive and it won't stop it from breaking unless you use some big bar 5/8" (#5) and lots of it.
The 6x6,10/10 WWM will keep the slab together if it breaks, and it won't break unless the base settles away from the slab.

Just so you know...all concrete cracks, but reinforced concrete stays together after it cracks.

I'll second what dirtrod said and add that now is the time to add a floor drain in the middle of the shop. I've had garages with and without and there is nothing better than being able to hose off the floor. If you are trowling the finish, the slope can be very minimal.

Good luck!

Well I've designed commercial buildings, for a living. Yes you could get by with a home garage and 4" of 2000psi@30days or completly unrated, but I would go for 6" fibermesh 3-3500 psi @ 30 days personally. I would only add #4 ( :rolleyes: )or #5 ( better :) )rebar @16" centers with 6" slab as the closer the rebar is to the ground or exposed the weaker your making the slab. Typically you need 3" clear on either side to make the rebar be useful within the slab. I'd only add the rebar if you expect a lot of traffic or very heavy concetrated loads. Your floor will take quite an abuse the stronger you make it the less likelyhood of having to cut it out and fix it later. Definately build footings for your perimeter and you could pour monolithic footing then the actual floor later. And underslab prep is VERY important. Compact to 90% would be optimal with 6-8" of aggbase over native. If you are in a clay area you may want to go with a deeper base. For the bridge cranes I've designed for even moderate loads of 5 tons we used footings of 18-24 square by 24 deep. But that is commercial buildings.

Don't forget to run any under slab stuff before you pour. I know that seems redundant but you'd be surprised. Drains, water, air or electrical lines.

Don't forget to plan slope for drainage. Typically 1/4" per foot but even 1/8" will move water enough to not stay stagnate on the floor.

From your description, consider power floating.

Dirtrod: Yes on the cracking or spalling. Most commercial floors are 6" but typically 4500psi @ 30 days. I don't design with WWM anymore in fact it's getting hard to find around here. It's difficult to keep centered in the slab (comparitivly) and fibermesh is just much easier.

Mine was 3/8" rebar 12" O.C. and tied into foundation. 6"concrete average 2" slope from wall to garage door.

I'll post pics for ya later.

some pics for ya:


http://www.imagestation.com/album/?id=4291945803

Tons of rebar AND tons of steel (for second story).

I think a 4" thick slab with a good 1" rock mix will be perfect for a garage floor. As long as you are not going to work on anything huge. Fibermesh is good but I don't know about a floor that you are going to be rolling around on. Wouldn't them little fiberglass hairs be a little scratchy.
Concrete is about $62 a yard/delivered around here.

45-65 yards sounds like ALOT. Unless your shop is just really huge I would recalculate...yards not cubic feet. If you really do need that much concrete...I am jealous.

I would do some sort of sealer instead of any type of paint. The paint on my floor didn't last too long. A sealer goes into the concrete so it doesn't wear off and keeps stuff from soaking in.

I think I would also thicken the slab where the hoist goes. If it is one of the 2 post hoists I would imbed some appropriate sized threaded rod in the concrete to bolt it down with. It just seems like with the 2 post it would put a lot of force on the floor if the vehicle were loaded improperly.

Dan

Hey there neighbor!:beer:

Don't forget that the frost line here in MI is 48" so build your footings accordingly.
BEST advice would be to check with your local city/township office to see what the codes really are for a garage floor. Keep in mind that you're getting advice from people all over the country and what may be ok there is't here and vice versa.
If I remember right if your shop is attached to your house you MUST have footings but if it's a freestanding building you could get away with a floating slab. But like I said before, your first stop should be your city/township office to check local codes and don't forget that building permit!!!:D

BTW you may want to go here http://www.concrete.com/calculatorsmaterials.htm#volume
and enter your shop dimensions.
I come up with only 29.5 yds for a 40'x40' slab at 6".
If you need 60+ yds. for a 6" slab you have a BIG shop!

Frost depth is 42" here in lansing. Yep, if attached it must be frost-proof to the depth of the house or min 42" (here). If it is a polebarn the slab wont have to be frostproof, just the post footings. I'm in the middle of a 40'X64' polebarn at my place and I'm gonna use 6x6 10/10 over 1" foam with radiant heat tubes in a 4" floor, I'm not worried a bit.
I currently design buildings every day.
btw, 45 yds is only about 3600 sq. ft.(@ 4" ), that seems very reasonable. :)

Also...in the winter you have about $5/yd. additional cost because the concrete plant has to heat the aggregate. Plus spring can have frost law/load limits which can cost a bunch if they can't haul more than a couple yards at a time.

http://www.challengerlifts.com/questionsanswers.html
addresses the floor issue...4-6" of 3500psi concrete at the post base.

Thanks guys, that is a lot of usefull information.

My polebarn/shop is a 40x40, but i am planning on adding 10' on one side, 15' on the front and putting in a 60x12 driveway at the same time. That is why I need so much concrete.

I will be checking with the township. I dont think I will be pouring it until the middle of July, so i should not have to worry about the loads.

If you guys dont mind I am sure I will be PM'ing a few of you when I get closer to actually doing this.

How much do you usually figure for the mesh or rebar in $$$$ per square feet???

For you Michigan guys that replyed, how much is concrete around here????

Thanks again for all the great info.

The sidewalk in front of my house is 5" thick with 6x6 :D strong as hell for a sidewalk but the guy running the bobcat dug it to deep and I got tired of back filling. So I just back filled with concrete. The patio out back is the same way with the ends tapered from 4" to 8" incase I put a roof over it to hold the weight of the colums.

My shop floor is 30x40, 6" thick fiber reinforced. No rebar, I was told the fiber was better.

I used to work cement. We would build ring walls, or foundations for oil tanks. Big fawking oil tanks. 140' diamieter! We used 20 miles, yes miles of rebar in the one. trying rebar sucks. Took a 5 person crew 3 weeks just to layout the rebar.

I would and have used just the wire screen. Reason one, cheaper, two easier, three rebar is not needed. 30x40 building 4-5" slab, no footers, with drains. The floor has a hairline crack above the pipe for the drains. This was expected. No disrespect to the guys that do this for a living. Just use the screen and pour a couple extra inches where the lift goes. No insterts needed, the lifts use cement anchors. Drill hole and insert. Also use a power trowel. Get the floor as smooth as you can, it makes it very nice when you have to roll around and sweep up.

C'mon now, go post tension!!! You will never have to worry about anything then (10-12" of concrete, with 5/8" wire rope run criss crossed 2' o.c. throught the slab tensioned to 10k psi.) I'tll only run you 20-30K!!! :)

Ok, I'll shut up now.

I don't know much about concrete, but I saw an idea in a buddies shop he just purchased that made lots of sense. One section of the shop has I beam layed out in a 4' checkerboard pattern on the floor. The top of the beam is flush with the concrete. This would make an excellent area for Iron fab work. Floor is completely level and you can weld holddowns on to the top of the I beam if you have to.


Just an Idea I thought i'd throw at ya!!! We all dream of the perfect shop, mine will have this when I can afford to build!!!:beer: :beer: :beer:

That's how we built my uncle's shop. We put railroad track down, so that it would be flush to the surface. It worked out really well. We've used it for laying out big project(trailers,frames you name it) We poured his 6" thick no rebar, just fiber. It's held up for over ten years now.