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Q.Within 60 days of pouring a concrete basement, some vertical cracks appeared. The cracks are between 1/32 inch and 1/16 inch wide, and extend from the top of the foundation wall down about 4 to 5 feet. My subcontractor tells me that the foundation is structurally sound, but the client is worried. Is this type of cracking normal, or can such cracks be avoided?

A.Jay Meunier, contracting specialist at S. T. Griswold and Co. in Williston, Vt., responds: Many house foundations will exhibit small hairline cracking from curing and shrinking. If the cracks do not enlarge much more than their present size, the foundation should be fine.

There are several possible causes of the cracks, including normal shrinkage from curing, and early backfilling of the foundation without bracing the walls. As concrete cures, it dehydrates and wants to shrink. Factors affecting whether cracks will appear on walls include the length of the walls, the number of wall penetrations, and the slump of the concrete.

Early backfilling can cause problems by placing extra pressure at the upper regions of the walls, where there is the least support. The pressure can cause small deflections in the upper wall areas, inducing cracks from the top of the wall down. You can check for wall deflection by running an offset string from wall end to wall end, verifying whether the distance from the string to the wall is consistent.

If the cracks continue to open up and lengthen as the walls cure, you should talk to your concrete contractor about your options for preventing water and insect penetration. If the cracks open up beyond 1/8 inch, the cracking may be caused by factors other than curing or early backfilling.