| Previously Submitted Questions |
| Q. |
A crack runs the entire length of the concrete slab in the basement. It is a hairline crack at one end of the basement and is noticeably larger at the other end (the end with the garage door). The owner said it happened the winter after the home was constructed (1992). It has not gotten any worse since then. What would cause the crack to occur so soon after the house was built? Can we reasonably assume it shouldn't get any worse since it hasn't changed in 7 years? The home is located in Cabarrus County. |
| A. |
The crack sounds like a shrinkage crack. Shrinkage cracks in basements are common. They are caused by contraction of the concrete as it dries out or is subjected to colder temperatures or both. They can be avoided, if the Builder takes special precautions during construction.
The only thing about your description that doesn't fit the rest of the evidence too well is that the crack is apparently wider at one end then the other. Shrinkage cracks are generally the same width from one end to the other. If the concrete varies in thickness, however, the crack can vary in width.
Shrinkage cracks are usually not a structural concern. However, they are unsightly and can allow insects to penetrate the slab. I would be more concerned if I thought the crack was caused by settlement. I don't think it was. The fact that it has not gotten any worse in 7 years is a very good indicator that it is not a settlement crack. It also means that you probably can assume it won't get any worse. |
| Q. |
Our driveway is only three years old yet it has several large cracks in it. What caused this? |
| A. |
Driveway cracks are usually caused by too much water in the concrete when it was poured, improperly spaced contraction joints, settlement, or some combination of the three. |
| Q. |
Our house has a basement. The floor in the hallway between the front foyer and kitchen noticeably slopes from right to left. What causes this? |
| A. |
Probably the right side of the hallway is solidly supported by a wall in the basement while the left side of the hallway is supported with a floor joist. The joist is deflecting (sagging) under the floor and wall loads while the support under the right side is staying put. |
| Q. |
Our house is on a site that slopes sharply from front to back. V-shaped cracks are appearing in the brickwork. What is causing this? |
| A. |
Probably the rear part of your house is founded on filled ground while the front part is founded on hard virgin soil. It is very difficult to compact fill well enough to avoid future settlement. Research has shown that even well compacted fills will settle up to a quarter inch per foot of fill. To be safe, the entire foundation should be founded on virgin soil. |
| Q. |
Some of the floors in my house vibrate and are springy. What causes this? |
| A. |
This problem can usually be attributed to long joist spans, the lack of bridging between the joists, the type and method of construction of the floor deck, or some combination of the three. |
| Q. |
We have lived in our house for seven years and there has never been any cracks in the exterior brickwork. This year a large crack appeared at one of the corners. How can this be explained? |
| A. |
Some of the soils in Charlotte contain large amounts of clay and are therefore susceptible to swelling and shrinking with changes in the moisture content. We have had especially dry conditions lately. Probably the soil under the corner of your house has a high clay content and has dried out enough to cause the corner to subside. |
| Q. |
We plan to build a new house. What is the best thing we can do to ensure we get good quality construction? |
| A. |
Take the time to find a good contractor. |
2008 Criterium-Simpson Engineers