Concreting Garage floor--how thick?

Discussion in 'Homesteading Questions' started by rio002, Aug 12, 2006.

  1. rio002

    rio002 Well-Known Member

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    Alright along with several other projects going on, I am going to concrete the garage floor, currently it is very hard packed dirt. I am going to have to do it a section at a time using 2x4 as frames probably about 4ft by 4ft squares. Question is --since I do plan on occasion to drive a car in there-how thick does it need to be? Does it have to be pure concrete or can I layer in some rock to cut costs of the concrete down? And if I lay the frame down level, does the ground inside the frame Have to be level, or can I just let the concrete fill in a little deeper in some areas (we're talking less then 1/2inch difference). Oh and since it will be done in sections, do I need to leave any space at all between the previous section and the next one being poured (for expansion/less cracking ect.) Any advice would be great I'm on my own for this one. :)
     
  2. rambler

    rambler Well-Known Member Supporter

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    I'm not real knowledgable in concrete work, but the _best_ thing you can do for a good, long lasting floor is get rid of black dirt (anything with organics in it) and put down 6 inches or so of good gravel & pack the heck out of it so you can't even see a footprint when you walk on it.

    Use rebar in the 'crete.

    If you do this, 4 inches of 'crete will do you fine.

    If you don't do this, 6 inches can crack & settle on you pretyy badly.

    You should be able to pour more than a 4x4 area at one time, that will be a lot of seams? You want a few cut crack lines to control the cracking. But every 4x4 seems excessive, and every different pour will be setting up a crack line for you.

    --->Paul
     

  3. rio002

    rio002 Well-Known Member

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    I see your point on the 4x4 sections, the fewer the seams the better, it is a 14x24ft floor. I bet I could bribe a buddy into helping and do it in 4 sections of 7x12 lol. I have rebar around but not much--any cheaper option other than rebar? I have been watching the thread on adding fibers to the concrete--could fibers replace the need for rebar?--or is rebar the end all be all for good floor? :)
     
  4. culpeper

    culpeper Well-Known Member

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    Here in Australia, the legal limit for concrete on which vehicles will be, is 10cm (4 inches). If the vehicles are over 1 ton, then it has to be 15cm (6 inches). Reinforcing mesh is strongly recommended. Most concrete garage floors here are finished without joins, unless they are double garages, where this is usually a join vertically in the centre.
     
  5. jehehmeyer

    jehehmeyer Longing for home!

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    6 inches of crete with steel mesh should do it. The "right" way, from what I;ve been told is to have a gravel/rock underlayment. I know some folks who skipped that. The steel mesh needs to be in the middle of the crete, so you will need to figure out how to do that (tie it to rebar stakes, stack it on rock, etc). Now for the caveat: I reccomend the above ONLY on observations I've made. :)
     
  6. CatsPaw

    CatsPaw Who...me?

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    4" is standard. Rarely is the substrate dead level. So, 4" is the minimum and usually there are thicker places somewhere around.

    Remove all top soil. Top soil is compressable and will allow the concrete to settle. Go down to subsoil. If you have to dig manually, cut it off smooth and level...i.e. don't dig down, making little craters and then filling them back in to make level spots.

    Generally speaking, a pro will dig away, then back fill with gravel and screed that off level. Different gravels will act differently. Sometimes a plate compactor will be used. Wet #53's would be compacted, while you can shoot dust in and it will generally stay exactly as put down. Gravel guys will tell you whatever you want to know. See if there's anything on sale that would work...(yes, types of gravel are often times on sale if they have too much of a certain grade.)

    If concrete is going to crack there's not much you can do. Those seams are actually called control joints. They are there to intice the concrete to crack in a controlled, "asthetically pleasing" place.

    Rebar...not so much.....Rewire better. Rewire is usually 6" x 6" welded wire and comes in a roll I think 3' or 4' wide. It's main function is to insure that when the concrete cracks, the two plates don't go techtonic on you and change elavations right next to each other. One control joint in a normal garage is about standard. 14 x 12's or 7 x 12's would work fine. Make sure reqire is contiguous throughout the floor. Using 2 x 4 forms the rewire will float underneath the form and some concrete [for the 4"] will flow out underneath the form. When you pour the next batch it will lock in with the rewire.

    Also, if your planning to heat it at any point I would lay sheets of blue foam insulation board down on top of gravel...say 1" or 1 1/2".

    Dig to subsoil, level off with a couple of inches of gravel, screed level, blue board, rewire, pour concrete.

    As you pour, use a hook to pull up on the rewire to get it in the middle of the concrete. Just stick it in the wet concrete and give it a few yanks here and there. Don't stand to close otherwise you end up just working against yourself.

    I've probably forgotten lots of advise, but, knowing me, I'll probably think off it and want to tell you about it.

    (I only think I know everything....'cause if I did know everything, I would KNOW I know everything instead of just thinking it....maybe I just stayed at a holiday inn express....I don't know. which takes use back...well....never mind. :)
     
  7. agmantoo

    agmantoo agmantoo Supporter

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    Place a vapor barrier between the stone and the concrete if you do not use the insulation suggested above.
     
  8. rio002

    rio002 Well-Known Member

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    Thanks all! I think I have a good plan worked out now, and I have plenty of welded wire fencing that should work in place of rebar. I knew I could count you guys to give me a good standing on this project. Thanks so much!:)
     
  9. rufus

    rufus Well-Known Member

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    A coworker years ago put that blue foam board that comes in 4x8 sheets down before he poured is basement and he said that he doesn't need a dehumidifier and in his garage, he doesn't mind crawling underneath the car in the winter for a little work. My garage/addition will definately have that feature when ever my ship comes in!
     
  10. ET1 SS

    ET1 SS zone 5 - riverfrontage Supporter

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    Fiber added to concrete will not replace the rebar.

    If you were doing a walkway where it will never take tons of weight then maybe, but never a vehicles weight.

    Plastic sheet, then board styrofoam, then rebar every 2 foot, then welded-wire, and pour 4 inches of concrete.

    And dont forget to include an oil-pit trench with concrete steps, so you can change your oil and be able to easily look around the undercarriage. those are worth a million, when you have them. You'll kick yourself afterwards, if you dont put one in.

    :)
     
  11. rambler

    rambler Well-Known Member Supporter

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    Here in Minnesota with lots of frost & lots of salt on the roads, rebar is _much_ prefered to wire mesh. The rebar is way better, and the mesh just rusts right off with all the salt that soaks in.

    The fibers are _not_ liked by some for a shop floor, as the fibers can stick up & itch a person working on the floor. I really have no experience with fiberconcrete, never been around it, but that is what some have said. Anyhow, not a replacement for iron, it mostly helps small surface crazing from what I understand.

    If you are using old wire, my understanding is that galvanized stuff should not be in concrete, it causes issues down the road. Such thin old wire is going to be real hard to fit in the center of the concrete, it likely will mash down & be laying between your floor & the gravel. But, it will be cheaper, sure.

    --->Paul
     
  12. Westwood

    Westwood Well-Known Member

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    Here in my neck of the AR woods, the ground doesn't move. Fiber in the 6" floor of the dairy barn indeed did replace rebar. No hairline cracks, not a one after 5 years. The dairy barn is now being remodeled into our home. Only problem is the institutionally approved slope to the drains. Level the floor or shim up the furniture? Cheaper to shim up! ;-)
     
  13. dennisjp

    dennisjp dennisjp

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    I have poured a lot more concrete than I care to remember.
    Catspan is right on just about everything he said, with a minor exception. The wire comes in 5 ft. x 50 ft rolls.
    And Agmantoo is right about the plastic. You can use 4 mil but if you are going to do it in sections, I would go with 6 mil.
    To start with, it sounds like you are going to mix it yourself. Do you have a mixer or are you going to do it by hand. If you are going to do it by hand, you are in for a lot of work. You would be better off hiring someone to pour it for you.
    You can buy ready mixed concrete for about 2/3's what it will cost you for the materials. Concrete comes in different grades. 2,500# mix is what contractors usually use to pour footings for homes and 3,000# mix is what most use for floors.
    I have always went with 3,000# for footings and 4,000# mix for floors because there is less chance of cracking. There is always a chance of cracking, and I don't care how much care you give it, but the higher the PSI concrete you use, the less the chance is.
    Catspaw was right about what he said about the wire. It will not keep it from cracking, but it will serve to keep it at the same plain if it does.
    If you are thinking of using quik-crete, don't. It will cost you far more than getting the sand, gravel, and portland cement. Way, way, way more than a truck would cost you. That is, if you poured it in one pour.
    You must buy the materials any way you pour it. I live in Va. and it sells right now for about $80 a yard, and at 4" thick, which is fine, that will cover 81 Sq. ft. You didn't say how big your garage was, but 24' x 24' is about normal for a two car garage. I have built one garage that was 28' x 64', but other than that, they were all 24x24, so that's what I'll figure on for yours and you can go from there. the square footage calls for 7.11 yards of concrete, but I always order more than required and look for a little somewhere to pour the extra, if possible. You are only talking $640 for the crete. And then if you talk to the people at the plant, they will put you on to someone that can pour it for you for about $25 a yard. That would be another $200. There is no way on Gods Green Earth I would mix and pour 8 yards of concrete and pay darn near the same price for the materials, if I could stand by and watch someone that knows what they are doing pour it and be gone in a few hours.
    Don't get them to do it all. That is where they bite you. Have it ready to pour and wait for one of them to get hungry. They run out of work just like anyone else does and they remember John over there that called about a job and will drop the price. Go for the small contractor, but ask the concrete plant about them first......
    Another thing. I wouldn't use the fence you have. Concrete wire is heavey gauge wire and the wire does rust away in concrete over the years. The smaller the wire is, the faster it happens.
    I learned early that it wasn't cost effecient for me to pour concrete if I didn't have too.
    I am disabled now, and I guess it is partly because of the concrete I did pour, and I only poured it when I couldn't get someone that does it for a living to do so and had to have it done to keep the job going. I still take a job every now and then, when the people know it will take me a week or two to get it done so I can work slow.
    Before I take a job, I call all the boys I know that does it for a living, and check to see if one of them will be idle when I can get it done.
    I then take my time and get it ready to pour. When I have it ready, I call back to see who is hungry and give it to them. The getting it ready is the money part. I can earn a thousand dollars fiddleing around for two weeks and pay someone else two hundred to do the hard part for me.
    With all of that sh@# said. Clear it down to solid earth to 8" below finished grade. Haul in enough rock dust to put 4" in. Screed it level. Lay down the plastic. You will need help with the wire, and be careful. It can cut you real bad. Roll it out and cut it to lenght, and cut it with bolt cutters, (easiest way). After you have cut it, turn it over and roll it backwards until it will lay flat. It can be agravating. Have your helper walk on it and raise it up until it will lay flat. Then carry it and lay it down inside the garage in place. Continue until you get it all placed. You can buy a roll of tie wire at the conctere where they sell the concrete. Use side cutters or even pliers to cut and tie the wire together at the seams so it will stay at the same hieght whe the crete is poured. Form the front door and if you use your phone. Call your man to pour it.
    There is a man hear that pours by himself. If you pour it, get atleast 3 friends, if you want a good job. Hope this helps. Been typeing for a yaer it seems, lol. Good luck. Dennis
     
  14. CatsPaw

    CatsPaw Who...me?

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    I'm very nearly at the same point you are. I'm going to be building a 24 x 40 workshop hopefully this fall, so, I've been trying to decide about pouring myself or not.

    I was contemplating putting PEX in the floor for somewhere down the road when I might be able to get an outdoor wood burner.

    If you were going to mix yourself, you might consider buying a mixer. You can get them for just under $200.

    What do you think Dennisjp.....about the 6th or 7th bag of mixing by hand and they'll be wishing they weren't?

    You could probably sell the mixer when you were done and recoup alot of it's cost.

    As Dennisjp said about extra concrete, order extra and form yourself up something like an apron in front of the door, or stoop by a service door or something small someplace else. If you have extra, drop it in the other place. If it's not quite enough, you could run and get some hand mix to finish it off and/or the small job is not so important that if you mess it up somehow or have to modify it on the fly because there wasn't quite enough extra, it's no big deal. Maybe a pad for a fountain that would look cool near the house or something you've thought about doing but didn't want to mess with a small amount of crete. You'll get the extra when you pour and kill two birds with one stone.
     
  15. dennisjp

    dennisjp dennisjp

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    The reason I said get extra is I was always doing contract jobs and if I ran out I couldn't hand mix extra and to order a 1/4 yard cost you as much as 3 yards for delivery fee. I would always order 1/4 to 3/4 yard too much. I did one job for a Ex police cheif and ordered excactly what it came up to. I had three people on the clock and had to wait for several hours for the truck and we added rock dust, packed, and leveled it until it was as perfect as it could be and I still ran out of crete. less than a quarter yard and it taught me. You can take some old wood and make some forms for stepping stones. I have two pcs. of 1/2" plywood that I made forms for 16" x 16" stones and sold every one I ever made either to the customer or a later one down the road.
    It's a waste to have to buy a quarter yard for over $200 and a waste to leave 1/2 or better yard on the truck to send back for free. Once they mix it, it's yours wheather you send some back or not.
    If you send a yard back, when the truck gets back to the yard they just add to it and someone else gets it for free if they have some where to use it.
    Marshall concrete here has poured a yard across the street from the plant in patches with the extras that come back that he stores cement blocks on.
     
  16. suburbanite

    suburbanite Well-Known Member

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    Rio, this is a job you don't ever want to have to do again, right?

    It is worth the extra expense to do it right the first time, especially since you live in a state where you have to worry about water and frost.

    You need at least 6 inches of gravel and 4, preferably 6 inches of concrete. If you go with 6, then you'll never have to worry about whether your vehicle is too heavy for the construction. You'll also need rebar (or that metal mesh the guys are talking about specific to concrete).

    Ortho and Lowe's and Sunset have books about how to do concrete work, that run about $25 in the hardware store. For this big a project with this much at stake, the money spent on such a book is a good investment. Most big-chain hardware stores have good return policies on undamaged merchandise, so you can always buy the book keep the receipt, read what you need taking notes, and then return the book in a few days. But if you're that hard up for money maybe this isn't the time to take on this big a project.

    Buy your materials in bulk from a rock vendor. Where I live, gravel for use under paving stones is about $4 for 25 lbs if you buy it in bags at the hardware store. If you buy it in bulk and have a pickup to pick it up at the rockery, its $36 a ton, half-ton minimum. (There's a delivery charge if you have them deliver it.). I've done pavers, not concrete--only read about concrete--the guys advice above about what kind of concrete is golden! Listen to them.

    One way to break up the cost might be to do the excavation for the finished situation now, but only put down the gravel. Then when you get money for the concrete you can re-compact the gravel, put in the frames and rebar, and have someone with a cement truck come do the pour all at one time.

    A garage floor is really something you don't want to have to mess with later because it is just such a hassle. Can you imagine having to pull all your vehicles and storage out and dig up what is there and replace it? Yecch! You also want to consider if you ever sell your property--having the garage floor made up to the local codes, even if those codes don't officially apply to your part of the county, will probably help you if you ever sell.