I suppose if anyone happens to stumble upon this Blog they may find the information useful. Of course the following information is for educational purposes only . I recommend you always contact a licensed contractor when performing any work on your home that has the potential for major repairs or defects such as those described below.
Recently I have received several calls from individuals who are experiencing water in their basement. Unfortunately with finished basements this is a big problem as damage to walls, carpeting, furniture and other items is not uncommon. So how does water get into a basement and what can be done to prevent it?
First lets discuss how much rain water can potentially collect around any given area of your home. A typical 1/2-inch rainfall will fill a 50- to 55- gallon barrel. Figure about a half gallon of water per square foot of roof area during a 1-inch rainfall. A 2,000-square-foot roof can collect about 1,000 gallons of water (accounting for about 20% loss from evaporation, runoff and splash) Typically this water is properly drained far enough away from the home by properly installed gutters and downspouts, both of which are very important in preventing wet basements, and proper grading around the homes foundation. If any of these areas are defective or improperly installed you will have a greater potential for water in your basement or crawlspace.
A common misconception is believing a basement wall that looks solid will alone prevent water from entering the living area. The fact is when you have water behind a basement wall it builds up hydrostatic pressure which puts a great amount of pressure on the wall. If you stand in a normal, dry basement, the walls around you are subject to approximately 12-15 psi of pressure from the earth surrounding the foundation. So long as water continues to drain properly around the exterior foundation, the concrete can withstand this normal pressure and you may never have a problem with a wet basement. BUT, if water doesn't drain as it's supposed to, such as after a very heavy rain storm when the ground can't handle all the water and drain it fast enough, the hydrostatic pressure builds up and this is when your foundation can develop leaks. Water will eventually be forced to the area with the least amount of resistance whichh often times happens to be your basement wall. Suddenly those apparent "harmless" cracks become water entry points. With enough pressure these cracks can grow substantially causing significant damage to your foundation requiring extensive repairs. So what can be done to prevent water from accumulating around the foundation?
The first step is checking your gutters to ensure they are properly slopped and undamaged. All gutters must slope at least ¼ inch for every ten linear feet to provide proper drainage. When gutters begin to sag or pull away from the home, typically the result of leaves or other debris accumulating in them or ice damming, they may not allow water to drain to the downspout opening. The result is water spilling over the gutter and accumulating next to the exterior walls. This defect can cause problems beyond having a wet basement involving damage to the homes covering.
Secondly you should check your downspout extensions to ensure they are terminating far enough away from the home. It is recommended downspout extensions terminate at lease six feet away from the homes exterior. When a licensed contractor installs the downspouts they should be placed in strategic locations so they can be properly extended. Often times I find downspout extensions terminating at areas where you cannot safely install an effective extension such as sidewalks, as a tripping hazard would be created. An improperly installed or defective downspout extension will allow water to pond around your homes foundation.
The third, and most commonly overlooked defect, is reverse grading. Reverse grading is when the soil around the exterior wall does not slope away from the home but rather slopes towards the home. In my experience as a home inspector I most often see this defect in areas where gutters are damaged and/or missing. Over time water washes away the soil causing slopes which allow water to percolate into the soil and build up around the foundation. The minimum slope requirement should be 5% for the first 5' away from the foundation (3" of drop) and then at a minimum discharge slope of 1% (approximately 1/8" drop for every foot of distance) from that point on.
When the above does not remedy your basement water problems it may be necessary to have a sump pump installed or have the basement properly waterproofed or repaired by a licensed contractor.
hydrostatic pressure (′hī·drə′stad·ik ′presh·ər) (fluid mechanics) The pressure at a point in a fluid at rest due to the weight of the fluid above it. Also known as gravitational pressure. The negative of the stress normal to a surface in a fluid. http://www.answers.com/topic/hydrostatic-equilibrium?cat=technology
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