We just moved into a brand new house. There are some cracks in the basement floor. I know it is common for some cracking to occur during settling, however; what is normal? The one crack runs from wall to wall and it has increased in size. The contractor had put a silicon filler in the cracks orginally and now the crack is twice the width of the filler. The crack is about 1/4" thick. At what point should we be concerned, and what can be done about it?