Hi all..........I'm working on building a new shop and need some advice on the floor. Are there any special types of concrete or added items I may need for concrete? Some have told me to use rebar...some say fiberglass........some said they use bits of wire in the concrete.........I just want it to be strong, as I am installing a 2 post lift in the future........Any thoughts? Thanks, Brad

Remember one thing all concrete slabs will crack. Some worse than others.
the reinforcing is there to keep the concrete from moving and becoming uneven when it cracks.
Fiberglass is ok but it is next to impossible not to have some of it sticking up in the floor.
I always recommend that wire mesh be used. Make sure that the wire is in the middle to 1/3 of the way up from the bottom of the concrete, not laying on the ground and pour concrete on top. Use stirups to hold it up.

definately use rebar tied in a grid of 16" if you are putting ant kind of load on.
24" grid will do if you are just parking your car or truck on it. The wire mesh is alright for patios and sun decks but if you are putting alot of stress on the slab go with rebar. Also If you know where abouts the lift is going put extra rienforcment in that area. Good luck

Check local building codes some areas don't alow just fiberglass reinforcement yet. You may also want to consider putting footers in where you are going to mount your lift. Most codes call for rebar overlapping in footers and remesh or a grid of rebar(on chairs) for the remainder of the floor. I agree with 3602daryl. I would supercede code and use rebar even if only mesh is required.

Are you going to work the floor yourself or have it contracted out?
How big of shop is it going to be?
Have you done any research on concrete?
I have always liked http://www.concretenetwork.com. It has anything and everything you need to know about concrete. Loads of info, but I am not sure if they have the required thickness/reinforcements for lifts.

Will be contracted out...........shop is 60 x 36.......I have been reading things on the web and asking friends about it..........just wanted some opinions of people who have done it already.........Thanks for the help

Assuming that the soil you plan on pouring on is stable and not backfilled, you could use 4" of concrete, preferably 4,000 psi no air and 1/2" rebar 2' on center each way. We don't use a lot of fiber mesh, I really don't like the look of all the fibers sticking up. If you are concerned about shrinkage cracks, cut control joints in 12' to 15' squares within 10 hours of pouring the slab. Make sure the water cement ratio is no more then .48 (i.e. don't let the finishers empty the ready mix truck's water tank into the drum to "help" finish) Make sure that a good quality curing compound is applied shortly after the finishers are done. I would also apply a sealer after thirty days. This will prevent oil and crud from penetrating the slab and staining it.

We do this stuff everyday. Let me know if you have any questions.

Let's first start by saying that most lifts only require 4" of concrete at 3,000psi. With waste factored in, your contractor should use somewhere in the neighborhood of 40CY of concrete if you pour 5 inches thick. Reinforcing does not need to be anything more than 6"x6" W.W.F. for a shop, especially if you take the time to prep the subgrade (ie compaction). I always suggest putting stone down to create a drainage layer along with a layer of plastic to create a vapor barrier.

As someone stated earlier, concrete crack and it is up to your contractor to saw-cut joints in your new floor to control the cracking. The 12'x15' grid suggested earlier would be perfect since it will keep the size of the cuts consistent throughout the entire shop. I would make sure that you contact the concrete supplier prior to the placement to make sure the right mix is ordered. Ask them about a 4,000psi mix used by the DOT and, if available, use ti for your floor. The DOT has tested that mix design, so you know it will meet your requirements. You will have to watch your contractor to make sure he does not add water once the truck arrives. He will try to do this because it makes his life easier (screeding, finishing, etc.), but it raises the water-cement ration and decreases the strength.

Once they are off of it, they need to apply a good curing compound that keeps the concrete from drying out to quickly. I would keep your car off of it for 7-days, so the concrete will have enough time to develop most of its design strength before being loaded. Talk to your concrete supplier about a self-leveling joint sealer (urethane) that you can use to seal the joints.

Feel free to ask any other questions.

-Wardster

Couldn't you just put some visqueen (spelling) down over the new slab to help keep it moist long enough to dry and keep adding a mist of water on top of it, for a duration of about 4-5 days?
Or is it just easier and better to add the compound?

Water is the best curing method. This method however requires that the slab be kept wet for a period of 7 days. Ideally, a pond would be used to completly cover the slab - very impractical. Covering with plastic is the second best method, also a pain. It requires that the plastic be in contact with the slab i.e. no wrinkles or bubbles. It also has a tendency to leave behind marks. The third best method is using a curing compound. In our business, that is what we use 100% of the time unless we are going to cover it with winter blankets.

I didn't read all the replies but just in case someone didn't say it put in pipes for floor heat. Even if you don't plan to use floor heat add the pipes. You might change your mind someday. It's easy and relatively cheap to do now.

Couldn't you just put some visqueen (spelling) down over the new slab to help keep it moist long enough to dry and keep adding a mist of water on top of it, for a duration of about 4-5 days?
Or is it just easier and better to add the compound?

Plastic usually is not good all by itself since you have to wait until the concrete set up enough to put it down without messing up the finish. Most contractors will "wet cure" with wet burlap covered with plastic or they just use burlene (both in one). It is more time consuming to do and requires a constant source of water to keep the surface wet for 7 days. A white-pigmented curing compound can be applied with a sprayer and does not require further effort once it is applied.

Thanks for the reply.

Reinforcing fibers (fiberglass) will stretch more than concrete under loading. Therefore, the composite system of fiber reinforced concrete is assumed to work as if it were unreinforced until it reaches its "first crack strength". It is from this point that the fiber reinforcing takes over and holds the concrete together.
For fibers reinforcing, the maximum load carrying capacity is controlled by fibers pulling out of the composite because fiber reinforcing does not have a deformed surface like larger steel reinforcing bars.(rebarb) This condition limits performance to a point far less than the yield strength of the fiber itself. This is important because some fibers are more "slippery" than others when used as reinforcing and will affect the toughness of the concrete .

Remember one thing all concrete slabs will crack. Some worse than others.
the reinforcing is there to keep the concrete from moving and becoming uneven when it cracks.

I can't tell you how WRONG you are. I have a 26x60 poured as one, no expansion joints, IIRC the rebar was tied at 16" OC, 12" beams, and 6" slab. I regularly pull in semi's and dumptrucks from 16-22k, not a crack one.......:rolleyes: ;)

my old workshop was 50x30 and the concrete was 8 inches thick !! (with fiberglass) it was 8 years old-no cracks either!! i did not say using rebarb was bad. i was defending the use of fiberglass, since it was getting a bad wrap. technique, prep work,etc goes along way! i just poured my new floor a month ago. this one is 100x60 and is a 12 inches thick!!! this one will last me a life time!

12" thick. Damn what do you plan on using it for.
That should last you kids, kids life time.

my buddy does concrete for a living. we use the barter system between us-plus he owes me a couple of big favors- so, i got a hell of a deal on it!. i am going to epoxy the floor myself next week. even with that cost- i am still way ahead. this one- is my dream work shop!!

my old workshop was 50x30 and the concrete was 8 inches thick !! (with fiberglass) it was 8 years old-no cracks either!! i did not say using rebarb was bad. i was defending the use of fiberglass, since it was getting a bad wrap. technique, prep work,etc goes along way! i just poured my new floor a month ago. this one is 100x60 and is a 12 inches thick!!! this one will last me a life time!

I wasn't quoting you, I was quoting wwpiga that made a HUGE generalization that was way off......;)

I can't tell you how WRONG you are. I have a 26x60 poured as one, no expansion joints, IIRC the rebar was tied at 16" OC, 12" beams, and 6" slab. I regularly pull in semi's and dumptrucks from 16-22k, not a crack one.......:rolleyes: ;)

Someone obviously did one hell of a job prepping the subgrade for you. That, coupled with the tight rebar spacing makes for strong concrete.:ro)

-Wardster

Someone obviously did one hell of a job prepping the subgrade for you. That, coupled with the tight rebar spacing makes for strong concrete.:ro)

-Wardster

You are right, that is what happens when you do things yourself.....;)

I am setting up to build a shop soon. I dug down to clay and repacked, with clay only, back to grade. My concrete guy wants me to let them polish the concrete to the point of almost burning it. He says that will stop oil and stuff from soaking in. He showed me a floor done that way and with a little water on it I would have slipped and fell. Any comments on his idea?

I am setting up to build a shop soon. I dug down to clay and repacked, with clay only, back to grade. My concrete guy wants me to let them polish the concrete to the point of almost burning it. He says that will stop oil and stuff from soaking in. He showed me a floor done that way and with a little water on it I would have slipped and fell. Any comments on his idea?

Yes!!! Let him do it....My shop floor was polished from 4 PM until about 9:30-10 ish.....

I also had about 4-5 inches of good select fill, plus I had road base as my floor for about 3-4 years before I poured so that is my good base for the concrete....

I would absolutly let him overwork it to make it like glass, it is a dream to sweep when it is polished up, and cleaning the floor of oil with MEK is a snap.... or Brakekleen for the quick touch ups.....

We "burn-in" alot of basement and garage floors because that is what the customer wants. However, what I have read tends to frown on this finishing technique. Our experience is that done right, it lasts as if it was finished by hand. I think the problem comes when the finisher gets on it before the bleed water is off the top and forces this water back into the surface creating a higher water to cement ratio at the top.

Another way to keep oil from staining the concrete is to use a high quality sealer and reapply it every several years as mentioned above.

Clay is a very poor soil to pour on. It is a very expansive. You shouldn't have any problems with heaving but I would put rebar 2' on center to be safe.

Make sure you hire a reputable concrete company. You get what you pay for.

Good luck.

We "burn-in" alot of basement and garage floors because that is what the customer wants. However, what I have read tends to frown on this finishing technique. Our experience is that done right, it lasts as if it was finished by hand. I think the problem comes when the finisher gets on it before the bleed water is off the top and forces this water back into the surface creating a higher water to cement ratio at the top.

Another way to keep oil from staining the concrete is to use a high quality sealer and reapply it every several years as mentioned above.

Clay is a very poor soil to pour on. It is a very expansive. You shouldn't have any problems with heaving but I would put rebar 2' on center to be safe.

Make sure you hire a reputable concrete company. You get what you pay for.

Good luck.

I agree on the clay statement...seeing as how my house is on clay and I have to keep my foundation watered to keep everything in check....

If you are gonna drop alot of money on concrete...the cheapest thing you can do is to take that clay out, and put in a good solid layer of select fill, and make sure you pack that good.....

no problem rolloffhill. i agree- a good sealer applied every couple of years really helps out in the stain department.

I also agree with the statement about clay, which is why it is important to prepare the subgrade prior to the installation of any concrete. This includes stripping all vegetation from the footprint of the pour, proof-rolling the sub-base to make sure there are no soft spots, and the installation of a drainage layer to handle any water (~4"-6" compacted). If you discover soft spots when proof-rolling, then you need to find the cause and make the necessary repairs. This could be as simple as removing the soft material and replacing it with fist-size rock compacted in place. The next step is the installation of a vapor barrier followed by whatever reinforcing may be required by code. That could be as simple as a welded-wire-fabric or a mat of reinforcing steel......it just depends on what types of loads your new floor will see.

-Wardster

I am setting up to build a shop soon. I dug down to clay and repacked, with clay only, back to grade. My concrete guy wants me to let them polish the concrete to the point of almost burning it. He says that will stop oil and stuff from soaking in. He showed me a floor done that way and with a little water on it I would have slipped and fell. Any comments on his idea?

The floor finishing he is describing is a burnished finish, this type of finish is super hard and smooth, this type of finish is spec'd in some warehouses and food processing plants, easy to keep clean,impervious to moisture and a lot of chemicals, I have seen this type of floor burnished with colored dyes to make really cool floor finishes(high end homes).
You need to consult with the local concrete supplier and they should know a comercial concrete finishing company that is familiar with this process.
This is the floor that I would recomend for the ultimate shop!