My husband and I are looking at a house and we noticed that there were a few cracks in the mortar of the cinder block foundation, in the basement under the garage. I have never seen this kind of foundation and I don’t know if it’s common or not. Also the house was built in 1987 and I had read that over time cinder blocks can “go bad” and rot is that also true… if you can't tell I’m a little worried …so if some one would mind giving me some piece of mind that would be great. Thanks for you answers and your time

If you see cracks in the foundation then I think that would be good reason not to buy the house. If I were seriously considering a house I would have it inspected by an authorized agency.

How big are the cracks? Some hairline cracks are not much cause for concern, a lot of big cracks could be. I agree with tickle, get it inspected.

It is faily common to see cracks in the mortar line of a block foundation wall. It is more of a concern if the crack cuts right through a block. Cement blocks will not rot but normal settling can break the mortar bond and can be tuck pointed. Is there any seepage coming through the cracks? If you carefully inspect the concrete floor you will see hairline cracks in several spots showing how the house has settled. Like Amricca points out small cracks are much to worry about. I agree that you should have the home inspected. I would never buy a home, even brand new, without a complete home inspection by a licensed inspector.

There are no cracks the blocks just the mortar... and I don't remember how big exactly but I think they looked about 1/2in thick maybe not even that wide also there is no seepage.. we will have it inspected and find out for sure. We just didn't know if they were common or not for the cinder block foundations to crack that that thank you for everything...

When you get your inspection write up come back here and tell us all the gorey details. "1/2in thick maybe" really? That's kind of big, we were thinking more like hairline cracks. 1/2" crack is about as big as the nortar line.

Are the cracks running horizontal or vertical? A crack of 1/2" sounds alarming and somehow you may want to incorporate a structural engineer. It is not uncommon to find a number of older residential houses constructed of CMU (concrete masonry unit) walls without steel reinforcement. As a result, larger than normal cracks can appear due to settlement (causing vertical or stepping like cracks) or excessive loads from the soil pressure like wet clay (causing horizontal and/or wall bulging). However it is not as clear cut and easy to determine as I have noted in this post. Hence I agree with all the previous post to obtain a QUALIFIED inspector/engineer.

You can also try to have the home owner obtain an engineer to provide an report and have your inspector review it...

Cements blocks can rot ( so to speak). If they were not sealed properly and water has been in contact with them for prelonged periods they can become soft and start to flake apart. A 1/2 inch crack is very serious. I would deffinetly have it inspected by someone who is qualified in block basements. I have had to replace entire basements that were inspected by a "home inspector" less than a year earlier. Place a straight edge on the basement walls... if the center of the wall causes your straight edge to "rock" any bit what so ever... you could have a problem. Just because the blocks themselves are not cracked does not mean things are OK. The first sign of block failure always shows up in the mortar joints first. Any crack, Any where over 1/8" is a major red flag!!
Mike