Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: SUNDAY, March 25, 1990 TAG: 9003310108
SECTION: TODAY'S HOME PAGE: TH17 EDITION: METRO
SOURCE:
DATELINE: LENGTH: Medium
Despite the pervasiveness of the problem, few home owners are aware of the causes of water leakage. According to Bill Anderson of B-Dry System Inc., "The first step in selecting effective treatment options is to discover the source of basement leakage, which vary from one basement to the next."
Common causes
One common cause of basement leakage is improper surface drainage, such as when a house is built against a hill. In many cases, this can be alleviated simply by regrading the yard to slope slightly away from the home's foundation, or diverting the waterflow to bypass the home.
Other common culprits include poorly positioned downspouts and missing, leaky or plugged gutters. Downspouts should direct water runoff from the roof to a discharge point several feet away from the house. A downspout that is improperly positioned to drain against the side of the house allows water to build up along the foundation wall, until the backed-up "reservoir" finds a weak spot to enter the basement.
Gutters should be cleared of leaves and debris at least once a year. Basement leakage from either of these usually is restricted to one spot, and disappears when the external problem is fixed.
There are a number of less avoidable, temporary sources of basement leakage including plumbing leaks, storm-sewer backups, outdoor flooding above ground level and condensation caused by simple "sweating" of walls in humid weather. Normal condensation usually can be corrected with the use of a good dehumidifier.
Pervasive problems
A high water table is the most pervasive and serious cause of basement leakage, and is also the most difficult to correct. A high water table can affect a home in several ways:
As the water table rises to or above the level of the basement floor, water becomes trapped underneath and leaks into the basement through cracks in the floor, points where drains enter, or at the joint between the walls and floor. This joint or "cove" is seldom watertight, since the walls and floor are poured or placed at different times during the construction of the house (walls are first, floors generally last).
Water also can seep laterally through the foundation walls, either because of a rising water table, or because the ground itself is saturated after heavy rains. Foundations in different parts of the country are constructed from a variety of materials, including poured concrete, concrete block, brick and stone. Poured concrete walls, especially those in newer homes, are the most resistant to leakage; however, they sometimes develop cracks or air pockets that allow water to get through, in addition to joint leakage.
Concrete blocks and bricks are themselves quite porous, so that water may seep directly through foundation walls when the ground is saturated or the water table rises. Water also can soak through the porous mortar joints between bricks, stones or concrete blocks. In addition, the hollow cores of concrete blocks may eventually hold water; thus when the water level within the blocks is higher than the basement floor, water seepage occurs.
"The most effective method for water-proofing a basement that leaks," Anderson maintains, "is an internal drainage system that is constructed along the inside perimeter of the basement, below the floor. This type of system will effectively drain water that enters a basement through cracks in the floor or walls, or that seeps directly through the walls, regardless of what material they are made of. It also helps to relieve pressure against these walls."
by CNB