My basement walls are made of concrete block. My house is 30 yrs. old. Recently, I have noticed that one of the vertical cracks on one of the blocks has gone from hairline width to approximately 1/8" in width. I have not had any flooding or water damage in my basement at all. Do you think this crack widening is a warning sign? How do I determine what the cause of this crack widening is? How can I control the crack widening or repair it permanently? Thanks a lot.