PicturesI have a new house under constructions and recently found many many cracks have developed on the concrete slab in the basement. The worst run along straight lines where the sections were poured. These don't have shrink seams in place, they are just cracking along a straight line. There are also some jagged/random cracks that extend off of these.
Here's the final pour for the slab; you can see it's a non reinforced non-structural slab.
My builder has asked the concrete contracting firm to take a look at it but said he things these are just shrinkage cracks and they will be sealed up before they are done.
I would appreciate opinions and learned assessment based on the pictures so I am prepared when the concrete company responds.
Best Answer
Those "straight lines" are control joints (as opposed to expansion joints). The contractor knows that concrete slabs invariably crack, and they install those to make the cracks less conspicuous.
That said, you do seem to have more cracks than I'd have expected, and they appear more open than is typical. The one is oddly close to the exterior wall. I'd ask your builder about backfill and compaction practices.