Basements leak water in through the joint where the floor and wall meet and through mortar joints, mostly after rain or snow starts melting are the most common areas basements leak. However water can come up through cracks in the floor as well. Surface water works its way to the foundation. As footer drains start to clog or drain slower over the years water builds up around the foundation and creates hydrostatic pressure around the walls and under the floor. Water is forced through the joint where the floor and wall meet and through the foundation wall its self. Clay absorbs the water under pressure and swells causing walls to crack and bow, also the same cracking happens under the basement floor.