Educate me on concrete please....

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Old 12-18-15, 12:49 PM
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Educate me on concrete please....

As I progress on my workshop I try to look ahead. In the early spring I would like to get the concrete floor poured. I have about convinced myself that doing this as a DIY project is impossible but I need to keep the costs down. The structure is 50x40 and I need the slab 4 inches thick, 8 inches thick in an area that I plan to put a car lift. I have figured this would take about 25-27 yards of crete. I stopped by the local concrete company today and found out the rate is about $100/yard plus $600-$800 for a pump to get it to the rear of the structure.....so I am looking at about $3500 in material. I am looking to hire a company to come in for a one day pour and knock it out. What would be a fair labor price to do this job??? What prep work beside the obvious leveling and tamping of the floor bed could I do so that all these fellas would have to do is show up and start pouring? I was planning to use 4000psi crete with 8x8 inch reinforcement wire bought at the local Lowes. This does not need to hold a tractor trailer so I do not anticipate using rebar. Any advice would be appreciated.
 
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Old 12-18-15, 01:26 PM
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I am not a concrete pro, but will give my two cents. I agree 100% that this is not a DIY job. You would need an army of friends to help, and after you see the finished results you will wished you hired it out.

While labor rates will vary quite a bit, it is always too to get a few bids. A good rule of thumb would be to double the material cost and that will give you an idea of the total job cost. In your case about $7K. Of course getting at least 3 bids is the best course. Before you do, you should try to prep the site as much as you can so they know what they have to work with.

I would suggest using steel mesh or at least some type of fiber reinforcement.
 

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Old 12-18-15, 01:36 PM
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Now if I could get it for about $7500 or less i would go for that for a professional job....thank you.
 
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Old 12-18-15, 03:39 PM
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Have to agree 100%, no way is this a DIY job!
 
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Old 12-18-15, 03:57 PM
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You didn't mention forming costs--both material and labor. Or are you planning on slip-forming the entire job?

I agree with using steel reinforcing mesh, but I would get mine from a concrete supply place instead of Lowe's (even if it costs a bit more). Fiber reinforcement is a waste of good money, in my opinion (based on personal experience, both with bridge decks and residential slabs).
 
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Old 12-18-15, 04:05 PM
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What prep work beside the obvious leveling and tamping of the floor bed could I do so that all these fellas would have to do is show up and start pouring?
As Tolyn said you would have to lay the mesh. Don't forget, the mesh has to be suspended. What about framing & the expansion joints?
 
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Old 12-18-15, 04:08 PM
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I think that just the prep work would be a killer and a finisher may not guarantee their work without having also done the prep. I would get bids on the entire job, prep, reinforcing and finish concrete.

You might also want a sump to allow you to drain radiators and such. More info on that if you ask.
 
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Old 12-18-15, 04:27 PM
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Agree with FURD. Preping will save you little and maybe be an excuse if contractors do a poor job. Have the concrete experts do it all.

BTW... there are only two types of concrete...Freshly poured and cracked.
 
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Old 12-18-15, 05:13 PM
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OK....this is the stuff I need to know about. Forming....if I can expect a labor estimate equal to the cost of materials....is the forming usually included? I just want to have a clear idea before I drag someone out for an estimate that is way out there.....I also do not want to get taken advantage of also. I mean if this pour is going to cost me 10-12 grand.....I will have to come up with a different plan. This pour does not have to be perfect....it is not a commercial garage nor is it a public place...it is a hobby shop for my retirement.

My father and I built 2 barns in 1976, the one I am working on now and a smaller one that was 25x35. In the smaller one we laid the concrete floor ourselves....with a mixer from Montgomery Wards.....which incidentally I still have and works. It took some time but the floor was smooth enough to raise hogs at first, then serve as my mechanics shop for years, and I walk on the same floor every day now that I have since converted it into my home. I have no doubt in my mind that it can be done, with enough time and patience. The difference between now and then is in 76 I was 18.....in 2016 I am 52.

Another thought I had was to lay a 1 foot starter ledge around the whole perimeter of the building by hand, then get a truck in to lay the floor in 3 or 4 sections. If I got a helper I should be able to screed and bullfloat a 40x15 foot section of floor level enough for a car to roll on.....shouldn't I?
 
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Old 12-18-15, 06:09 PM
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Oops, made a mistake, ignore__________________________
 

Last edited by Pulpo; 12-18-15 at 06:26 PM.
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Old 12-18-15, 06:14 PM
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Forming is always included if it's a complete job, start to finish. Just don't expect someone you hire to do just the finishing to also include the forming, for free. Purchase some decent 2 x 4s, and do the forming yourself. Just remember to use a very taut nylon mason's line to set the top of the forms to--roller coasters have their place, but a large garage/shop floor isn't one of them.

Breaking the job into 4 separate longitudinal placements is a good idea, because it makes setting grade relatively simple, along with making finishing a lot easier (gives you a place to stand on while bull-floating). An obvious drawback to separate placements would be having to rent the pump multiple times. If it would work for you, try to find a ground pump instead of a crane pump--it will be considerably cheaper (last time I rented one, it was $500 for a whole day, with operator). The concrete supplier needs to know that the mix will be pumped, too, so they can furnish a "pumpable" mix. Normal chute mixes are too harsh for pumps to handle, without watering them down to the point of ruining strength and durability.
 
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Old 12-18-15, 06:40 PM
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Now Bridgeman that was helpful. The fella at the concrete company said he could chute the crete a max of 25 feet. The structure has a 15 ft sliding door on each end. I figured out 10 yards will do a 40x20 foot section 4 inches thick. I can build the 40x20 form no problem on each end and have the middle 10x40 filled in at a later date....maybe 3 weeks later. I would incorporate 1/2" rebar sticking out the ends to join the slabs. The question is do you think that myself and 2 other workers shoveling like hell can get that amount of crete spread and creed off before it starts to set. If I am not mistaken bullfloating comes later after the top water has evaporated....correct? This may be the ticket but a few more questions if I may....
1) would I need to put expansion joint material between the slab and the cinder block walls?

2) would supporting the mesh screen on cinder bricks be appropriate?
 
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Old 12-19-15, 07:02 AM
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It is best to support the metal mesh on "chairs". Google "rebar chair".

Actually, I didn't think of breaking up the pour into several pours. IMO that would be doable as a DIY job. I would still get the mud from a plant though even though I do know the mixer you are talking about, my FiL has the same one.
 
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Old 12-20-15, 01:48 AM
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I can't speak for the ability/durability of your "3 guys," but if they're of normal strength and able to work, you should be OK. Hint--don't break out the beer until everything is completely done.

Placing the mesh on bricks or concrete blocks is perfectly adequate--"dobies" are often specified by state DOTS, and consist of nothing more than small concrete blocks with a wire attachment to hold the mesh/rebar they're supporting. Walking around on mesh supported by loose (not attached) concrete blocks runs the risk of displacing the mesh off of the blocks--not good, as mesh on grade does absolutely not good, even though many "professionals" make that a normal practice. And yes, do install expansion joint filler at the exterior perimeter, to enable the slab to "give" a bit, without crushing/spalling, as it expands with changes in temperature. And don't forget control joints in the slab as well--either grooved at least 1" deep in the mud, or sawcut right after initial set, about every 10'.
 
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Old 12-20-15, 02:34 AM
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Now these expansion joints every 10 feet...many people say to do it but in garages I look at I do not see them, all I see is a solid concrete floor. It would seem to me they would be a big PIA in rolling equipment around over such as a cherry picker with an engine attached to it. Thus in that respect I need some help here. If I got hung up on a joint with a heavy piece of equipment it could be dangerous. Why do I not see these joints in regular garage floors? I can understand then in sidewalks.
 
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Old 12-20-15, 06:36 PM
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Expansion joints are not the same as control joints--you are confusing the two terms. Control joints every 10' or so, grooved or sawn as I mentioned previously, serve to control the location of normal cracking that occurs in slabs. If you are content with random cracks occurring anywhere and everywhere in your slab, fine, then just forget about installing any control joints. FWIW, sawn control joints are usually no wider than 1/8" or 3/16", and are easily traversed with most steel-wheeled implements or dollies. Depending on the skill of the finisher, grooved joints can be much more difficult for implements to pass over, as they are much wider than sawn joints

Placements greater than 50' or 60' long will also (usually) have at least one expansion joint, designed to compress when a slab "grows" with increases in temperature. Most expansion joint fillers (the same stuff I suggested you nail to your stemwalls, around the perimeter, to provide a cushion between the slab and walls, and to establish grade for finishing, are 1/2" or 3/4" thick, and usually 4" (or more) wide.
 
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Old 12-21-15, 02:36 AM
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Thank you very much for all the info bridgeman.....now I understand. I agree with the control joints since that you have explained them. This thread has been most helpful in pointing me in the direction that I need to go. I think I will do this job in slab sections....easiest way to go and within my budget. When I do I will post my progress under the projects section.....in fact I think I will start a project thread this week to show the whole conversion of what I am doing. I have gotten a lot of good advice from this DIY forum and am glad I found it. Thank you to all who contribute to my inquires....your opinions and help are greatly appreciated.
 
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