Larry Diamond - Keeping Basements Dry

by Larry Diamond

With the costs of single-family homes climbing out of sight these days, many homeowners have reason to take a long, second look at the house they already have. A full basement is often the largest room in an entire house and offers the potential for serving several purposes as additional living, working, and storage space. And converting a basement to living space is unquestionably cheaper than buying a new home, with the additional long-run benefit of increasing the value of the house.

If dampness or even occasional flooding is preventing you from enjoying your basement, this booklet will help you identify the source and cause of the wetness and will describe specific remedial action you can take.

First you need to spend some time down cellah, as they say in northern New England. In most older homes, the basement was designed only to be the place where the foundation of the house was located. It was never meant to be part of the living space. It was where pipes and wires came into the house and where conduits carried out waste water and sewage. It was where food and other things not subject to rust or mildew could be stored.

When the water table rose during a rapid spring thaw or after a heavy rain, it rose right into the basement. In anticipation of possible flooding, storage space in old basements was on shelves or platforms above the highest water mark.

Today, furnaces, hot-water heaters, and other major appliances are placed in basements and an occasional flood can be disastrously expensive. Fortunately, waterproofing technology has improved with the times so that the homeowner can be assured of getting high-quality products to remedy his particular problem.

The degree of waterproofing will depend on what the space will be used for. It you plan to use it regularly as a den, recreation room, or bedroom, then a high degree of dryness will be necessary to make the room comfortable. If you plan to use it just for a workshop or utility room space, then you will be able to tolerate a little more dampness, though it is wise to keep a light coating of oil on bare metal tools to prevent rust from forming. The method of waterproofing will be different depending on the usage.

In a workshop or utility room where function is more important than decoration, an unsightly floor drain into a sump at the low point in the basement will control any flooding. But if the room is to be completely finished off and used as regular living space, then you will want to be sure that the foundation walls are repaired and completely waterproofed, and that any drains or pumps be located outside of the living space. This is a more costly solution, but it is also more thorough as well as esthetic.

Few homes today have dirt floor basements. When asked how to convert a dirt floor with stone wall foundation into regular living space, a University Extension Service agent replied, Build an addition. He explained that it would probably be cheaper in the long run because the cost of pouring a cement floor and installing extensive drainage systems would be enormous. He suggests converting the attic or adding on as better ideas.

It basically comes down to this: If your basement has a severe flooding problem, complete waterproofing will be very expensive and time consuming. If you are willing to put up with minor water problems in return for using the space more for utility purposes than living space, your cost savings will be substantial.

Life exists on this planet because of an interchange between the earth and the sun, an interchange lubricated with water. The ground we walk on is designed to be an enormous spongy repository of water that can deliver nutrients to the roots of plants that become food on the table. When we enter the moist, life-sustaining skin of the earth by digging or excavating for the foundation of a house, we must keep in mind that we are intruders. Unless we take substantial action, the water and the soil will try to reclaim the space we have taken.

It will be helpful to take a moment to understand the nature of the beast water and how it behaves underground. Gravity is our main ally. It takes the rain water or snow melt and tends to draw it straight down through the soil. Water will not move very far in a lateral or sideways direction unless something gets in its way such as a layer of heavy clay beneath the surface high ledge, large stones, or other subsurface debris, either natural or manmade (such as building scraps filled in by the contractor). The direction the water moves underground is referred to as drainage. All things being equal, if the drainage area is of porous soil and free of obstructions, then a dry basement should be relatively simple to maintain. Few are that fortunate, however.

Even in areas with the best drainage, there is still a considerable amount of water near the surface. Water clings to soil particles like a sponge. This normal level of moisture is the culprit for dampness problems. Because the soil is right up against the foundation walls, any cracks or weak spots will let the dampness into your cellar.

The foundation walls must not only hold back tons of soil but also the water contained in that soil. That water can exert a tremendous amount of pressure against the foundation. Soil itself is not a problem because its particles are so relatively large. The liquid water, however, can find its way through the tiniest opening. Pressure the water exerts on floors and walls is called hydrostatic pressure. Water seeks its own level, the accurate folk wisdom goes, and your foundation is in the way. The ground water surrounding your foundation behaves the same as water in a container such as a tin can. As long as there are no holes in the can, no water will get out. But if you think the water only wants to come out the bottom, take a nail and poke a hole in the side of the can. The water spurts out until the level in the can is below the hole.

Standing water exerts pressure against every surface with which it is in contact, and the deeper the water, the greater the pressure. That is why your ears pop at the bottom of the deep end of the swimming pool, not the shallow end. It is the nature of basements that the weakest point, the wall-floor joint, is also at the deepest level and exposed to the greatest hydrostatic pressures.

So before we start spending lots of money on repairs, we now know what is going on down there. Like prisoners digging an escape tunnel with a spoon, hydrostatic pressures are slowly working away on the foundations of our homes. We are as oblivious as the prison guards until after one spring downpour we discover the basement is flooded.

Water gets into your basement by means of any one or a combination of these ways: leakage, seepage, and condensation. Seepage is sometimes referred to as capillary action, which is not entirely accurate. Capillary action will be discussed under seepage because that is the behavior it most closely resembles.

Leakage refers to the condition where water freely enters and flows into the basement. Leaks tend to occur at any point where there is a break in the wall or floor surface. For example, leaks frequently occur at the point where pipes pass through the wall, at corner and floor joints, around basement window frames, at support post footings, or through a crack in the surface caused by settling or poor construction.

Leaks occur when a large amount of water builds up against the walls or floor of your basement and cannot adequately drain away. Seeking its own level, the water forces its way through a weak point and pools up on your floor.