Where are the basements in new homes in Chapel Hill and the Triangle Area of NC? Marianne Howell Wright Certified Eco Broker,Triangle Area Real Estate That’s a question I get a lot from out of state clients so I thought I’d show you a basement under construction and talk about why we don’t have many in this part of NC. The first reason basement building is limited is our heavy clay soil. Water won’t drain through the soil away from the house and an underground basement would be wet. Another reason is foundations should be dug 12” inches below the frost line which can be 5 ft. in the north but only 18 inches in NC. It’s just not as cost effective to build a basement here. A builder will add $30,000 to $80,000 to the cost of a home (depending on the size of the house) for an unfinished b... 09/26/2011