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Proper foundation drainage is the first line of defense against basement leakage and seepage, and will go a long way toward creating dry, useful space below grade.
Many people live with damp or moldy basements and assume that’s just the way it is. Some basements flood every time heavy rain or melting snow saturates the soil and exceeds the capacity of the drainage system or sump pump. Over 60% of basements have moisture problems or flooding, by some industry estimates.
Excessive moisture and periodic flooding severely limits the use of basement spaces for storage, recreation, and utility space. It is especially problematic in finished basements, where moldy materials lead to musty odors, deterioration of materials, and allergic reactions in many people.
In an existing home, the situation can often be greatly improved with better management of surface water: rain water from the roof and water that collects around your house. If that doesn’t solve the problem, you may need to address subsurface water as well. Improvements to subsurface drainage are costly and difficult to retrofit. In new construction, however, good foundation drainage is easy to achieve and affordable.
Unfortunately, some builders skimp on foundation drainage in new construction because the work is mostly hidden from view and is not a hot button like granite counters or a soaking tub. But money put in the ground for better drainage is money well spent. A small investment in site drainage will yield big dividends in the form of warm, dry space that you can use for storage, work space, recreation, or added living space.
Plus a drier basement will reduce moisture problem in other parts of the house – even the attic or roof – as basement moisture travels up through walls and chases due to the wintertime stack effect.
Unless you are trying to build in a swamp or place a full basement below the water table, then it is not difficult to build a dry basement. It requires attention to three main strategies:
• Surface water. Use gutters, downspouts, and good surface drainage to quickly move rain water and snowmelt away from the foundation. Read more
• Subsurface water. Use granular fill below and around the foundation combined with footing drains to collect and discharge water that reaches the foundation. Read more
• Waterproofing. Protect the foundation wall and slab with coatings or membranes to block the entry of water vapor and liquid water. Read more
These three approaches work together. If surface water is not properly managed, it becomes subsurface water. If too much subsurface water collects around the foundation, the column of water within the soil builds up hydrostatic pressure and any dampproofing and waterproofing techniques may fail.