Expert: Joe Turner - 12/18/2008

Question
QUESTION: Dear Joe,

I have a question about cracks on the floor for my new house. The house is at the Central Florida region, which a builder is still building for us. Currently, the foundation, the pipes, the walls and the roof are done with the dry wall installed at the next step. But I noticed there are three very long cracks on the floor around the sink pipe, two of which extend to the boundary of the foundation and are at least 30 feet long. The size of the crack is less than 1/8'' wide and less than 1/8'' deep currently since the slab is only one month old. I was wondering whether you can tell me what you think about the crack. What causes the cracks? Where can I find an engineer to inspect them? Thanks!

Shawn

ANSWER: Concrete does crack. Most cracks are the result of drying and the subsequent shrinkage. These cracks are mainly at the surface. You have described a crack that could be more serious.
Here are the danger signs in concrete slabs:
1. If the crack extends to the edge of the slab, you have a potential problem. While it might not develop further, the potential is there. I would get a warranty from the builder that specifically addresses the crack.
2. Width of the crack. Generally, cracks that exceed 3/16" in width over a 12" run should be corrected by the builder.
3. Displacement. Cracks that are higher on one side - displaced - suggest and through and through crack that should be corrected.
Your cracked concrete is in the #1 category at this time. I recommend the steps described in #1, above.
JT

---------- FOLLOW-UP ----------

QUESTION: Thanks, Joe. Your answer is very helpful. Can you explain more about item 1? what potential problem should we expect? Can you also suggest what should be included in the warranty? I saw a 2005 house with 10 year structure warranty had a step wise crack about 1/2'' wide across the garage wall. This 2005 house was built by the same builder. But the builder just claimed it is not structure issue when the owner had difficulty in selling the house with such a crack this year.

Many thanks for your help!

Shawn

Answer
Sorry for the delay in answering your follow-up question. I must have overlooked it.
A crack that continues to the edge of the slab suggest a process that is extending the crack. At best this process has stopped. However, if you have offset - one side higher than the other, the crack is clear through and needs to be repaired or replaced. This is the step-wise crack you mentioned.
Unfortunately a few builders will try to avoid repairing things like this. But the law is on your side and if the builder refuses, it might be time to call the law, that is, get a lawyer.
JT