Garage Concrete Slab - Rebar Schedule

[dfkrug]

Here's another reason to use #4s and not #3s: When the #3s are delivered, many of them
are bent. So, I stopped buying them. #4s do not cost much more.

I would buy the #4 rebar by the ton, which is a bundle of 150-count 20-foot sticks. Usually none
come bent. My slabs all got #4s on 12" centers. The delivery guys know how to handle
these bundles.

 

[Egon]

Or go to Portlant Cement site and read up on concrete. They will have all the information. Concrete design and quality has a few more variables than just slump. And slump is controlled by more than just water content.

 

[Pettrix]

Here's another reason to use #4s and not #3s: When the #3s are delivered, many of them
are bent. So, I stopped buying them. #4s do not cost much more.

I would buy the #4 rebar by the ton, which is a bundle of 150-count 20-foot sticks. Usually none
come bent. My slabs all got #4s on 12" centers. The delivery guys know how to handle
these bundles.

Out here a #4 bar at 20' length is $5.00 delivered per stick

So for my pad that's around $280 in rebar.

9 yards of concrete or $975 in concrete ($108 per yard for 4,000 psi mix)

That's $1,252 in rebar and concrete. Not a lot of money for the materials. Labor is another story.

Waiting on the costs for that. I would do it myself but I don't have the experience in pouring a slab. I have laid rebar but never poured a slab.

 

[Streetcar]

+1 to egon comments
Water/cement ratio is important, but slump is influenced by several items
Properly curing concrete slab will reduce cracking
Concrete cracks for many reasons, controlling the cracks is important for longevity of your slab.
Closer spacing of rebar will help control cracks
Proper placement of reinforcing depends on loads in slab.
Because of its low strength it is hard to keep mesh in the proper position during a concrete pour

 

[coolreinfarm]

I built a 24x40 garage 10 years ago with a 4" thick floor and no expansion joints, when it was poured they put wire down and used fiberglass reinforced concrete, well no cracks yet no fibers sticking up and I have parked some big tractors on it and keep the suv and pickup on it all the time. I live in the midatlantic and we have some 0 deg weather. The Amish poured it and told me to wet it down every night for 5 days, if it cures too fast it will crack, they were right.

 

[TheMan419]

I spec out everything I want on my bid sheet, and hand it to the estimator.

If they look at it, and start saying. "You don't want this, and you don't need that", I thank them for their time, and say goodbye.

When I put my current barn up, I hired out the framing. The first two contractors tried, (unsuccessfully), to convince me, I didn't need concrete poured in the holes for the poles to sit on. That, a precast "plug" would be just fine. I was also told, I didn't need, laminated poles, or a steel plate, in the header for the O/H door.

The third guy who came out, looked at my spec sheet, and said, "Okay, no problem".

That was the guy who got the job. :thumbsup:

I don't believe any of my specs, were overkill. The laminated poles are straight, they don't shrink, or twist. The poured concrete doesn't settle. And, that header didn't sag in the middle.

A few of my customers, whom I do repair work for, are engineers. They often spec, what I do consider to be ridiculous levels of overkill.

I just made two laundry room shelves for one, that were 1.5" thick, solid wood. But, that's what he wanted, so I made them. :confused3:

If you want the rebar 12" o.c., find a guy who will do it, without questioning you.

Depends on the reaction from the contractor. Could be that he is saying this alternative will work just fine and save you thousands of dollars. Of course if you counter with no this is what I want and the cost is fine and contractor still argues with you that is a different story.

 

[AGRIMAN]

I built my 50x50 red iron shop about 6 years ago. The floor is 6" thick with 24x24 footers under each door. There is no rebar in my floor only concrete reinforced with fiber. It's used daily and we drive the tractors, combine, backhoe, skid steer and semi truck in and out all the time and there are no cracks anyway.

The area were we built the shop had a high spot in the middle (clay hill) We cut it down to grade so we ended up with a rock hard foundation for our floor.

It was poured and finished (slick) by an old time concrete guy.

 

[newbury]

<snip>
The main reason concrete cracks is from too much water in the mix. Water increases volume, and when it dries up, the concrete is still covering the same amount of area, but with less volume to it, so it cracks. Rebar holds it together. The more rebar, the smaller the cracks.<snip>

I thought the main reason concrete cracked was because it is concrete and that is the nature of the beast.

 

[Tractor Seabee]

House and garage slabs today are more commonly reinforced with fiber in the mix and no steel. Cracks are usually caused by poorly compacted subgrade, excess mix water, and shrinkage of the concrete as it cures. Cracks are the most commonly prevented by saw cutting grooves or troweling them in during placement called control joints. This is a complex subject with a lot of variables.

For quality work and proper advice select a contractor that is American Concrete Institute (ACI) certified. Your local concrete supplier should be willing to help you with the proper specification for your project as they know the ACI standards very well.

Ron

 

[Pettrix]

The rebar costs are a no-brainer. At $280 for the rebar, it's inexpensive.

Someone mentioned going higher than 4,000 psi. The norm out here is 2,500 psi so when I called out for 4,000 psi, the contractor was surprised at the high psi. They use 2,500 for footings and slabs. So my 4,000 psi is higher than normal.

Rebar doesn't stop cracks but it stops cracks from becoming really bad and turning into structural cracks.

Concrete is strong in compression but weak in lateral tension, that's why they use rebar. A slab is strong as long as it's got solid compacted AB underneath it. If the ground underneath shifts, the concrete will snap and crack. The rebar will prevent it from breaking away.