Q.: Why is an expansion joint used between the perimeter of a basement floor and the wall?

A.: When there is no separation provided between the wall and the floor there are likely to be points where the two elements will interlock. Expansion joints (which are really isolation joints) permit differential settlement of the wall and the floor. Also, the floor and the wall usually shrink at different rates and the difference in amount of shrinkage is likely to cause the floor or wall to crack if they interlock. The perimeter joint prevents this problem.