Flooding Cause - Clay Soil
Our heavy clay soil contributes to basement flooding in 2 ways:
- It blocks the flow of water away from the backfill zone
- It swells and cracks concrete walls and floor
Water trapped between the basement wall and the undisturbed clay soil may eventually seep through the basement wall. Or, as the clay soil gets wet and swells and then dries, powerful forces crack basement walls and floors as shown below.
Referring to the first frame of the illustration, we see a large hole or excavation much like a swimming pool. When filled with water, the undisturbed clay soil swells and expands, creating a barrier that could retain water for weeks.
If, instead of digging a swimming pool we were to excavate a new basement, the same reasoning would apply. Any water percolating into the soil on the outside of the walls would remain trapped within the backfill zone as shown in the second frame. With time, rainwater or snow melt could soak into the backfill zone.
The third frame of the illustration shows unwanted water in the backfill zone. Powerful pressures from swelling and shrinking clay soil crack the concrete walls and floor. Cracks become pathways for water to enter the basement.
So we see that water entering the backfill zone either seeps into the basement or enters through cracks in the concrete.
Preventing water from entering the backfill zone is the answer.