The Importance of Foundation Drainage

Water drainage problems lead to millions of dollars in damage for homeowners every year. By controlling water and properly waterproofing your foundation, you will prevent serious damage and help maintain the structural stability and integrity of your home. Before having any type of foundation repairs and waterproofing undertaken, you need to ensure that suitable drainage is in place. First, let's understand the meaning of foundation drainage.

Foundation drainage is nothing more than a system designed to divert water away from a foundation. Regardless of the waterproofing treatment applied on the foundation, drainage solutions are a must, or else water can easily overwhelm the foundation. Just remember this simple fact: water can only be diverted, it can't be stopped.

Apart from direct and heavy rains, underground water and roof run-offs are the major contributors to a damp basement. Proper foundation drainage involves simple techniques but it is quite a physically demanding job. The amount of time and effort required for installation will vary depending upon the size of the foundation and the amount of incoming water.

The first thing needed for foundation drainage is to have a proper slope around the house. Usually a slope of an inch per foot is adequate for a distance of 5 to 6 feet (or 1/2 inch per foot for a minimum 10 feet or a 3% slope). However, homeowners must ensure that there is no water stagnation within 10 feet of a foundation.  The earth around the house should also be compacted, so that the soil is "tight" and the slope will not deteriorate over time.

In cases where creating a proper slope is not possible, then you should opt for a peripheral area drain. Another option in such circumstances is the installation of French drains at a safe distance away from the foundation.

Components of a proper foundation drainage system include:

  • Well-maintained gutters and downspouts that are directed below the soil surface
  • Sufficient distance of trees from the building or foundation (should not be closer to the structure than their mature height)
  • Consistent soil moisture (ensure that water can drain from the soil and be replenished effectively)
  • Surface water drainage (ground should have minimum slope of 3% to move water away from the foundation wall)
  • Channel drains (to trap water and direct it away from the foundation)
  • Foundation drainage boards (installed on the outside of concrete walls to direct water to the drain tile, used in conjunction with waterproofing membranes)
  • Subsurface drainage made from rigid drain tile (either connected to a sump pump system or directed to daylight exposure)
  • Drain pipes placed alongside the foundation footing
  • Conforms to building codes (international code requires drain pipe for most structures with concrete or masonry below grade)
  • Geotextiles and synthetic materials (many modern drainage systems now incorporate these materials to prevent fine soil particles from passing through and clogging drain pipes)

Some experts might suggest installing a dry well which is simply a hole that has been dug - the deeper the better - and filled with crushed stone to increase the percolation rate. A nearby ditch can also offer a means of evacuating water if one exists. Some basements also have a sump pit inside the home in which a pump can be installed to remove excess water. A pump that keeps running is typically an indication that the water table is high where you are located or that the drainage is inadequate.

Appropriate drainage is a key factor in foundation waterproofing systems but is often ignored. The materials are inexpensive and if the work is done properly, it will last a lifetime.