When considering the most appropriate form of prevention and/or management, several factors need to be considered.
- Identifying the source of the water or moisture (90% of the time it is surface water)
- Severity of the problem
- Frequency of water penetration
- Budgetary concerns
- Foundation type (basement or crawlspace)
- Foundation material (poured concrete, concrete block, stone, etc.)
- Determining need and feasibility for prevention or management or both.
- Methods for Controlling Surface Water
The easiest method to prevent surface water from entering the home is to direct the water away from the home. The simplest method to properly divert water away from the property is to use a gutter and downspout system in conjunction with proper surface grading around the home.
Back To Top
If gutters, downspouts and grading cannot prevent the surface water from entering the basement (or crawlspace), an exterior perimeter drain is the last method for preventing water penetration. The exterior drain collects the water that accumulates next to the foundation and redirects the water away from the foundation.
In basements and crawlspaces where water penetration cannot be prevented, water management systems such as trenches and sump pumps are used to collect the water that enters the home and redirects the water out and away from the home.
Methods for Controlling Groundwater
Groundwater that enters the basement is best controlled with a sump pump and/or an interior perimeter drain. The sump pump and interior perimeter drain collect the groundwater that rises to the basement slab (or crawlspace floor) and redirects the water away from the foundation.
Method for Controlling Excessive Moisture Vapor
All foundation materials (such as dirt floor, concrete slab and walls, or block walls) are porous and allows some moisture vapor to pass through from the exterior. In addition, the cooler temperatures in crawlspaces and basements create a condition that actually draws in the moisture through condensation. In homes where excessive moisture vapor is present, some control method should be used to prevent problems with wood destroying insects and fungus. In basements, when moisture penetration is slow, the most common method for controlling moisture vapor is with a dehumidifier. In crawlspaces, moisture vapor penetration usually comes through the soil floor and is usually controlled with a vapor barrier and crawlspace vents.
Exterior Surface Grading
Back To Top
The grade or slope of the soil should be designed to direct surface water away from or around the home. Water accumulation next to the home can lead to water penetration problems such as structural damage to wood framing, interior damage to finished surfaces and damage to the homeowners' belongings. Additional problems such as hydrostatic pressure against foundation walls or surface water mixing with expansive soils next to or under a foundation can lead to cracking of the slab and foundation walls. Proper grading (in conjunction with a gutter and downspout system) is one of the easiest ways to manage surface water, reduce the possibility of water penetration and structural damage from hydrostatic pressure, and control the water content in expansive soils.
Grading of the Soil Around the Perimeter of the Home
The soil around the perimeter of the home should slope away (at a minimum of 1/2 inch per foot over a minimum distance of 10 feet) from the house to prevent rain water from accumulating next to the foundation. Soil in this case does not refer to the topsoil but the layer of soil that is impervious to water such as clay, which directs the water away from the house. Many times the topsoil is porous (as would be used for planting) and absorbs the surface water. The sub-layer of clay or similar non-porous soil prevents the water from continuing in a downward movement and directs the water laterally. If non-porous soil next to the foundation slopes toward the house, water will begin to accumulate.
Grading of the Lot
The overall lot grading is also an important concern since surface water may enter from adjacent properties. Generally, if the house is located on a slope or on a lot that receives water run-off, swales are often used to direct the water around the house. Swales are shallow ditches or depressions in the landscape that capture the water run-off. Then, like a small creek, the water is directed around and away from the house.
Gutters and Downspouts
Back To Top
Gutters and downspouts perform two main functions. First, they help capture and direct the roof run-off water away from the house. Second, they help protect the exterior surface and perimeter grading of the home from water damage that can result from the roof run-off water running down the side of the house or eroding the soil around the home. It is estimated that a one-inch rain fall on a typical 2000 square foot roof can produce up to 2,500 gallons of water. Not all homes need gutters and downspouts, depending on the design of the house and local weather conditions. But if the home experiences problems resulting from surface water, gutters and downspouts should definitely be a first line of defense.
Gutters come in different shapes and sizes and should be selected based on particular conditions of the home, including aesthetics, slope and size of the roof, and local weather conditions. The standard gutter is made of aluminum or galvanized steel and is attached to the fascia board at the eaves (roof line of the home). Other types include plastic and copper gutters, wooden gutters on older homes, and integral (to the roof) or built-in gutters on some newer homes. The standard gutter is 4 to 5 inches wide. The size of the gutter should match the anticipated amount and volume run-off for the roof.
Downspouts, sometimes called "leaders," are used to direct the water leaving the gutters down to the ground or drainage system in a controlled fashion. Downspouts are secured to the side of the house and are often constructed of the same material as the gutter. Where the downspout discharges the water is important when controlling surface water around the home. Extensions, additional piping that extends laterally from the bottom of the downspout, are used to direct the roof run-off away from the foundation. Splash guards, or blocks, are used to prevent soil erosion if the downspout discharges onto the ground.