Our new home driveway has aprox 20 fine cracks.

The driveway is (2 car wide) and about 40 feet long. There are 2 (15 x 15) slabs and 1 (10x 15) at the edge of the road. I was told the smaller slab at he driveway edge of the road is thicker and has rebar in it.

ALL the sections have cracks in them. Some meet and form a square in the middle of one section. The most of the cracks run along the center lengh of the driveway. But some run sideways too.

I have had 2 different people that know concrete look at it and they both believe the driveway did not have enough stone compacted under it before the concrete was poured.

The home is still under the (one year) home warrantee. The builder says fine cracks that do not shift in elevation or get more than 1/8" wide are not structual problems, and it does not have to be addressed.

There is an extended warrantee, but it specificaly says it does not cover concrete that is not part of the foundation of the building.

I say it is only a matter of time, and we will have a mess thet we will have to replace. Does anyone have any ideas on how to get the builder to take responcability for this driveway before the warrenty is up?

Bob in Temple, TX

 

The issue is probably not the compaction of the stone base...it's that there are not enough joints in the slab. There should have been a joint down the center and then joints across the driveway creating ten sections, each 7.5' x 8'. If correctly jointed, the cracks would all likely have occurred inside the joints as designed.
If you want to prove to the builder that it was done incorrectly, do some research in the ACI (American Concrete Institute) manual. This is the standard book by which concrete practices are specified and judged. Look in the section regarding contraction joints in slabs on grade. There are rules about jointing slabs such as the maximum distance between joints, the depth of the joints in relation to slab thickness, etc. The way you describe it, I'm fairly certain that your slab would not meet ACI standards. You can find the specs online.
Other than that, the builder is correct. If their statement about cracks is in the contract as you noted, you would probably lose in court. If you bring up the ACI specs and prove negligence, you would have a good shot at winning.

 

Okay, I just looked it up online and the spec is that contraction joints in slabs on grade should not be farther apart than 24 to 36 times the slab thickness in inches. Assuming your 15' wide slab is 4 inches thick (standard), the joints should not be further apart (in either direction, lengthwise or width-wise) than 144 inches. Your driveway is 180 inches wide so if you wanted a symmetrical joint pattern, it needed a joint lengthwise down the center. Likewise, the sections made by the joints should be as close to square as possible, and should never be more than 1.5 times as long as they are wide. Therefore, following ACI specs for a 4 inch thick slab on grade, the contraction joints should have been as stated in my first reply.
There are extenuating circumstances. For instance, a lot of guys use 2x4's to form concrete. A 2x4 is really only 3.5" tall, not really 4". Therefore, a lot of concrete is only poured 3.5 inches thick. If this happens, the joints need to be closer yet. The same if the concrete was poured too wet...more contraction joints would be needed to control cracking.
Do some research yourself and print it out. If you have proof like that, there's little that the builder could dispute. It would also benefit you to get a representative of a ready mix concrete company to come out and explain the aci spec better. They wouldn't want to throw the contractor (their customer) under the bus, but aci specs are basically the bible of concrete. If you asked specific questions, they would probably answer them truthfully.

 

Thanks for the info Pecos.
I tried to look up the actual specs online and only found sites leading me to buy books for approx $150. I am going to visit the library and try and find a page to copy and present to the builder. I spoke to a rep of the builder again and he did say that the city inspected the work and it passed. Does this mean I really have a problem with the city?
Would you have a link to to a site that allows download of code books?

Thanks for your help.

Bob in Temple

 

I just googled it and found the info I gave you online. Moderators of this site do not allow posting URLs so I can't just google it again and then post where I found it. In short, you can find the info online.
I doubt that the city inspected the actual concrete work. They probably inspected the site before the concrete was poured to make sure it was thick enough, etc. That's what they do here. Call the ready mix company (that makes and delivers concrete in mixer trucks), and have them send out a quality control guy. Ask him about the specs I gave you. You should even be able to get a copy of the aci specs from them.

 

City and county building departments are not in the quality control business. They go through the motions to ensure that basic specifications are met, and that's about it. I've been told in no uncertain terms by more than one AHJ representative (in several different states) that quality control is the responsibility of the owner.