Moisture in Basement: Waterproofing, Walls & Soil Moisture

Sandy(light) — 1.25 units of water per foot of soil

Loam (medium) — 2.25 units of water per foot of soil

Clay (heavy) — 3.67 units of water per foot of soil

This list makes clear that the heavier soils have a significantly higher carrying capacity, which means much more ground water is kept near the surface in the vicinity of the foundation. More water also means that greater pressure is exerted against the walls and floor.

In heavy soils, the only satisfactory solution is to excavate the perimeter of the foundation and install drain tile and waterproof the wall.

If there is no waterproofing on the wall (there should be a coating of tar or other water-repellent material) then regardless of the soil type, excavation and waterproofing will be necessary.

Excavation is a job for a person handy with a shovel, or for someone with a couple of strong-backed friends. Otherwise, consult several contractors for estimates before deciding which one to hire.

Contractors generally give estimates in terms of dollars per linear foot. To get the total cost, measure the perimeter of the house and multiply that number by the cost per foot.

(Homeowners are warned to beware of advertisements for services claiming to be able to waterproof the exterior walls of the foundation without excavation. Several companies report success using a clay injection or a pressure pumping system that forces a waterproofing material down evenly spaced holes drilled around the foundation. They state that the material spreads out underground and fills in the space between the holes. There are currently, however, numerous law suits filed around the country by homeowners for recovery of payment in cases where the treatment failed to stop the leaks.)