As we mentioned earlier on the page covering foundation materials, many of the design decisions made about the foundation are involved with insuring that water will not be able to penetrate the basement interior. The material selected is important in this regard but the drainage design is even more important.

    Drainage designs can vary from extensive interior and exterior loops of drain tile or piping to no drainage at all. The image to the right represents a house that has included an interior loop of drain tile which terminates in a sump pit. Water is thereby channeled to the pit and then pumped from the house. The inclusion of the interior drainage loop allows the builder to use sand or gravel and still insure that water can be moved away from the structure before it enters the basement.

    Another very common drainage design here in Maine is to connect the interior loop of drain tile through the footer which goes to an exterior loop of drain tile. This will permit the water to be led away from the foundation often if the site plan permits the drainage is directed towards a lower portion of the lot where it can terminate in a dry well or, quite commonly, be left open to daylight. Once again the builder has incorporated a lot of empty space below the structure. This too will increase the negative pressure exerted on the soil, and consequently attract more radon towards the home.

     So, what is the solution? There actually is no ideal solution. Every builder, every homeowner has to walk a delicate balance between risking a very costly water problem and  less expensive potential radon problem.

    After a while a radon contractor will become familiar with the area that they work in. If they can be provided with the location of the home and the radon screening results, They will have a pretty good guess at the foundation design and the type of material and drainage below the slab. This is because these two factors - geology, and foundation design are so important in determining the amount of radon attracted to the structure-