I am I first-time homebuyer. I found a 2001-built colonial home that is nearly perfect and am preparing to put a bid on it. HOWEVER, the basement floor has cracks. The cracks are in an interesting pattern, which I hope will help one of you better identify what the problem is, how serious it is, can it be fixed & for about what about cost, and ultimate should I proceed with this home, drop & run. As I said, the concrete basement floor has cracks. The unfinished basement is about 40 feet x 50 feet with a traditional basement door in the middle of one concrete wall leading up to the back yard. IF it matters, to one side of the house is a small creek, about 70 feet away. The creak is set low, that is, it about 4 feet below the plateau of my land. Back to the cracks. The cracks are about 1/4 inch in width. Now, when I say cracks, there are actually only two big cracks. The two straight-lined cracks are perfectly perpendicular to each other and create a cross with its center point directly in the middle of the basement. In other words, the cracks split up the basement floor in to four almost-square equally sized quadrants. It's this cross that is the interesting pattern, which I assume means something specific. That's it. I would greatly appreciate any advice on this issue. If this is a huge problem, then I don't want to even waste $1,500 plus on getting an inspector & making a bid. Thanks for your insights.

The pattern you describe suggests that the cracks are shrinkage cracks. Are you sure about the size of the slab being 40 x 50 FEET?? That is an enormous house. If those dimensions are indeed true, the floor should probably have been poured in sections, with control joints placed almost exactly where the cracks have appeared.

Keep in mind that ALL concrete cracks. The usual device used to prevent VISIBLE cracks in floors are wire mesh, fiber or reinforcing bars embedded in the slab, and the use of control joints to limit the size of each individual section of the slab. These measures make the cracks microscopic in size, and multiplies the number of cracks astronomically. If such measures are not incorporated into the design of the slab, what results is fewer cracks, but very large ones.

Keep in mind also that what I've offered here is a seat-of-the-pants guess based on your description, and it's no substitute for an on-site evaluation by a design professional.

How serious it is depends on whether water ever enters through the cracks, whether the cracking is getting worse or is stable, whether the floor is still level, or is there any vertcal displacement from one side of a crack to the other, the soil conditons under the slab...lots of questions that are best answered by a professional on site.

The cure could range from doing nothing, to patching the cracks with hydraulic cement, or less likely, to removing and replacing sections of the slab.

Richard,

THanks for your quick response. Although I have measuredn you're probably right, that is, the dimensions of the basement are probably smaller. After akkm the entire two story house is 1,892 sq ft. on a .46 acre lot. Would the significantly smaller dimension impact your assessment of what the problem is? Lastly, if we must do your third option, ie remove and replace sections of slabs, what might that cost? Thousands, 10 of Thousands?
Meanwhile, as you suggested, I will have someone actually look at it. Thanks for your input.

The cost to remove and replace some of the slab would probably be many hundreds or very few thousands. It would entail saw-cutting some straight lines, jackhammering out the concrete between the lines, and pouring new concrete in the nice straight strips thus created. That would be the very worst case. Possibly, patching the cracks with hydraulic cement would be sufficient.

If the cracks are shrinkage cracks as I suspect, then they probably have done all the cracking they will do, since the house is 5+ years old, and if there is no vertical displacement, patching ought to be enough.