Concrete driveway

MariposaTraicioneraSeptember 24, 2009

Our driveway is about 20 years old, and has been cracking for several years now. It even looks like it is sinking in some areas. From what I see, the concrete is only 3" thick, and there are no steel rods below.

I mention steel rods because a company who came out to give me a quote said that it needs to be at least 6" deep and have steel rods criss-crossing below.

What do I need to know before I accept one of these quotes (besides the obvious: references)? I am trying to be an informed customer so I will know what I am going into.

Would appreciate any advice on this topic. BTW, it is a regular 2 car garage, so not a wrap around drive, just a straight drive up from the street to the garage.


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Compaction of the base beneath the concrete is important as well. 6" with wire mesh is a standard in most areas, but it all depends on your soils type. In some areas, it needs to be dug down deeper than 6" in order to bring in a crushed base material that meets the proper compaction requirements before the concrete is poured. This is mostly in areas where it is sand based native soils or areas of extreme wet conditions. If you dont know about your local conditions, you might get a consult from a soils engineer that knows your area and can advise.

    Bookmark   September 24, 2009 at 6:30PM
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You definitely should have steel mesh (or cross tied steel rebars) in (not below) the new driveway slab. Concrete is very strong in compression but not so strong when subjected to decompression (stretching) or shear (sideways) loads. That's where the steel comes into play by strengthening and stabilizing the concrete thereby making it more crack resistant. You don't say where you live, but if it's a cold weather climate a 6" slab is probably a good idea. In a climate without cold winters (i.e. freezing and thawing) 4" is probably adequate although the extra thickness never hurts, just adds some cost.

    Bookmark   September 24, 2009 at 6:59PM
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Typically the mesh should be supported off of compacted soil before the pour midway to 2/3 down from the surface of the concrete. Out here it is common practice to "lift" the mesh up as they pour. I dont subscribe to that method as there is too great a chance of not pulling it up far enough, or pulling it too close to the surface interferring with the finish. The newer fiber re-inforced concrete is often used in patios, porches, sidewalks without the use of wire mesh but it does not finish well and would not recommend it for a drive way/garage. I would personally never pour out a driveway less than 6" in any area.

    Bookmark   September 24, 2009 at 7:50PM
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Thanks for the advice. I'm in Oklahoma, and we get some very cold spells, with ice storms.

The cost is the same for 6", this is what the contractor does around here. He said he never does 3".

    Bookmark   September 25, 2009 at 10:19AM
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These are the meausurements of my driveway:

17' x 36' with 3/8" rebar.

Sidewalk: 4' x 22'.

One expansion in the middle.

The contractor did not add the 6" to the quote, so I need to have him put that since his "verbal" quote was about doing 6" deep. His price is $2,875.

Does this sound okay? This was my first quote, and the only reason I asked him was because he is working in my street on the neighbour's yard.

The old driveway is done in parts, but this guy is saying he will do it with two parts starting at the top of the garage to the bottom near the street. What is best?

    Bookmark   September 26, 2009 at 3:03PM
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That's around $4.10/sq.ft. It's typically over $5.00 sq.ft. out here for drive/sidewalks, flat pours in general.

Always a good idea to start at the house and work towards the street whenever possible.

    Bookmark   September 26, 2009 at 4:51PM
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I am getting another quote tomorrow, and am not as concerned with the price as I am with the company doing a good job. What I find puzzling is why the contractor said he would do it in two parts (length) rather than the six squares I have now. I don't know how to explain this. The old one we have now has grass and weed growing up between the joints, and he is saying that having just two joints would be better.

    Bookmark   September 29, 2009 at 6:04PM
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Sounds like your original driveway had issues with compaction (as mentioned). What is the proposed spacing for the rebar? Also, I would prefer control joints every 7 or 8 feet. IMHO one control joint in 36' is not nearly enough.

    Bookmark   September 29, 2009 at 6:46PM
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I got an interesting contractor today. He said that my driveway is stable, and the only area that I thought was sinking is not really sinking. He said that I can repair it by having all the 1" pieces of wood and weeds removed, then he would blow whatever out of there, clean it properly and install backer rod and use Sikaflex. These are the joints where the pieces of wood filler that was used have come out. The cracks he said were superficial, and unless I had money to blow and wanted a brand new driveway, he felt like it would last another 5 years at least.

Now I don't know what to think. I'm shocked that a contractor wouldn't try to have me go for a new one!

    Bookmark   September 30, 2009 at 5:01PM
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I'm shocked that a contractor wouldn't try to have me go for a new one!

There are still a few honest people left in the world. Of course, in five years who are you going to call? In the intervening time, who will you recommend to your friends?

    Bookmark   October 1, 2009 at 10:47AM
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I'm in New England, in addition to what's been mentioned here are some other specifics that I have included in contracts:

-4000psi minimum mix
-4" slump max
-6% air entrainment
-No water added on site
-1/2" rebar, 12" on center
-Float with magnesium bullfloat prior to bleed water showing, final finish will be a broom finish
-Control joints max 15' they are always drawn out on paper instead of letting the concrete crew decide where they go
-Expansion joint against house.
-After broom finish, cover slab with 6-mil plastic sheeting for cure.

I always tell the guys that when the truck delivers the concrete, I want the ticket. The "ticket" shows all the specifics of the mix, the driver will bring it with the concrete. The ticket even shows what time the load was mixed. I once had a truck show way late, kept getting the runaround from the driver. When he showed we checked the ticket, the mix had been dispatched 6 hours prior. I declined acceptance and sent him away with a full truck.

    Bookmark   October 3, 2009 at 10:54PM
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In northern Illinois, we use a 6-8" base of a grade C8 for a base, compacted (pea gravel is not acceptable). The concrete is a min 5-7" depending on if fiber or 4x4 mesh is used or nothing. Remember 4x4 wire mesh is only good if its hooked into the middle of the concrete.

What the ground excepts it rejects, with that said, the base will make the most difference re: sinking. The strangth of the concrete has a lot of veriables ie ash content, air ratio, etc.

    Bookmark   October 4, 2009 at 7:41PM
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