Waterproofing Basement

Where's the water coming from?

Basement walls suffer from the same ills that plague the other walls in your house, and they have one special problem of their own: moisture. If the walls sweat or if puddles of water collect on the floor, it's a time to fight back. A wet basement wastes space, and it could undermine the footings and foundation walls of your home. There are four possible sources of basement moisture problems. Simple tests help you uncover the culprits. In tracking down the water's origin, don't neglect the possibility that the moisture may be the result of a combination of these factors.

Condensation

Symptom: Mold and mildew, damp walls, rusty metal, and dripping pipes. To test for condensation, tape a mirror in the dampest spot and wait 24 hours. If the mirror becomes foggy, or beaded with water, suspect condensation.

Cause: The cause is moisture-laden air from an internal source, or the temperature difference between the walls and the inside air.

Solution: Improve ventilation, install a de-humidifier, or seal the interior walls.

Seepage:

Symptom: Dampness on the floor or a particular wall, especially near floor level. As with condensation, tape a mirror to the wall. If moisture condenses behind it, seepage is the problem.

Cause: Surface water is forcing through pores in the foundation or wall-floor joint. Check roof drainage and window wells.

Solution: Improve surface drainage. If the problem is minor, an interior masonry sealer may work. If not, waterproof the foundation from the outside.

Leaks:

Symptom: Small areas where water seems to be oozing or even tricking from a foundation wall or floor. Check the damp area carefully, note condition of mortar joints between blocks.

Cause: Cracks may be from normal settling, or an abnormal condition such as faulty roof drainage or improper surface grading.

Solution: A single hole may be plugged from inside with water proof hydraulic cement. Or, you may have to work from outside by waterproofing that exterior surface or installing perimeter drain tiles.

Underground water:

Symptom: A thin, hard-to-see film of water on the basement floor could be the first sign. Test by laying down vinyl sheet goods or plastic for two or three days. If moisture is penetrating, it will dampen the concrete underneath the barrier.

Cause: A spring or a high water table is forcing water up from below, under high pressure in most cases. This may happen only in rainy periods.

Solution: Drain tiles installed around the perimeter of the foundation or floor might direct water to a lower spot or a storm sewer, or you may need a sump pump.