Cold Seam Crack

DEAR TIM: The builder we hired to build our house just finished pouring the foundation walls on Monday. It was a very hot day with temperature in the 90's. After the forms were removed, to my dismay, I found these V-shaped lines in the wall. Are these cracks in the wall?

I got very worried and called the builder. He said these are not cracks and nothing to worry about. I asked a neighbor and he also said not to worry. Still, I am not convinced because I didn't see these lines when I look at basement walls of other new construction in town. Should I worry about structural damage and/or water leakage? To prevent later, I did ask the builder to spray the waterproofing UTC foam on top of the tar. Any advice on what else I can do? Thank you very much! Liang F., Westport, CT

DEAR LIANG: Looking at your photograph, these lines look like cold seams. Poured foundation walls can have cold seams where one batch of concrete gets hard while the next concrete truck is making its way into the job site. Or if the flow of concrete was stopped in one area while being poured in another. There may not have been enough workers to keep the concrete flowing properly.

These are potential weak spots in your foundation. They may be okay if there is enough reinforcing steel, or rebar, in the concrete.

Cold seams can be caused by delays in pouring the foundation. PHOTO CREDIT: Liang Feng

Close-up of concrete cold seam. PHOTO CREDIT: Liang Feng

Column EM0050