Of all the calamities besetting the household nothing compares to the damage that can be incurred by good old water. Because in instances of rot, mildew, insects and structural degradation each process usually started with a water leak somewhere in the foundation.

Building a home with a basement entails building a cocoon to keep out moisture. Cement by its very nature is porous and acts as a wick for water if there is no place else for the water to go. This is especially true in clay areas where the dirt particles are tightly packed and water movement is slow or non-existent. Water will find its way into the foundation through cracks and seams or any other opening.

Waterproofing the Foundation

1. Concrete Coatings

In most home building a foundation is poured and then left to dry for a week or so. Next a special tar is sprayed over the concrete where it will be underground. This forms a waterproof skin on the concrete preventing moisture from entering. The downside to this sort of treatment is that the installation may not be even or there might be moisture still in the walls which can be trapped by the coating and cause a small imperfection which can be exploited by ground movement and made larger. Another possibility is that sections may be scraped through during the backfilling operation. In addition when the foundation settles there may be cracks in the basement wall, fissure which may stretch and even compromise the outside coating creating a riff where water can get through.

2. Waterproofing Membranes

Most membranes are thick rubberized-asphalt sheets which adhere to the concrete and seal up the seams from the footings to above the ground. The concrete is first treated with a primer to promote bonding and then the membrane is pressed on. The seams are sealed tight with a roller. This type of material can also be used to repair the fissures in cracked walls.

Another form of membrane is a dimpled polyethylene product that is attached to the wall. The air pockets behind the sheet allow any shifts or settling of the home to be compensated. These coatings protect the wall against hydrostatic pressure and direct the water downward and away from the footings.

Waterproofing the Ground

Installing a French drain is something almost all new building contractors will initiate. The system allows water to go straight down below the footing where it is angled to flow away from the foundation. It is not an extravagant cost when building a home as the materials consist of 4" perrforated PVC pipe and ¾ -1" inch crushed stone.

How the system works is that the pipe encircles the home below the footing and uses gravity to pull water low away from the foundation. The crushed rock allows the water to drain easier. When the home’s footing and foundation walls have been poured and and sealed, either by tar or membrane, crushed stone is poured around the outside of the walls and the footings. The crushed stone pathway is angled downward to accept the water and move it easier toward the drain and away from the home.

A small trench is excavated away from the foundation and directed toward the downward or lower side of the property. This will aid the water in finding its way from the foundation to the natural drainage of the land. In this way the ground water is aided around the foundation and channeled away from the home.

Perforated 4" pipe has holes in all directions to capture the moisture in the ground. There are also holes on the bottom, and this seems strange until it is noted that water tables differ depending where you are. In an area with a high aquifer the water will seep upward where it is trapped by the pipe and channeled out.

Crushed stone covers the pipe up to almost ground level where, in the case of a new home or re-excavation, 2-4 inches of top soil can be put down for sod. Many foundation experts will advise a landscape fabric to prevent the dirt from filtering down into the gravel and clogging up the system.

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