Why Do Basements Flood?

Leaks, Cracks and Seepage

• A leak or crack in the foundation can cause a wet or flooded basement. Rainwater can collect in window wells and enter through cracks. Excessive watering of plants, shrubs or turf adjacent to the structure may also force water to seep into the basement. If surface water runoff from melt or rain events is directed towards the structure rather than away, it may eventually penetrate the walls.

Overflowing Eavestroughs or Downspout Problems

• A basement may flood if roof water is not directed away from the foundation, which may occur if there is no guttering, if the guttering is clogged with debris and water is overflowing as a result or if downspouts are clogged. Water should be forced to drain, not allowed to puddle. Water may collect if the downspout lacks a splash pad or elbow.

Weeping Tile Failure

• Weeping tiles, or foundation drains, that are clogged or improperly installed can cause basement flooding. These drains are installed around the house exterior below the basement floor, and, when properly functioning, intercept and dispose of subsurface water under the house. If the drain is not working, water will build up behind the foundation wall and eventually seep into the basement.

Sewer Problems

• If excess storm water enters the local sanitary sewer system, it may become overloaded if the water level in the system is higher than it was designed for. This condition is known as surcharge and can cause flooding if a house has floor drains or fixtures below the surcharge level. Flooding of water and sewage may occur if a system lacks a backwater valve or if the valve is not operating properly. This valve should automatically close and block sewage entry if sewage backs up from the main sewer.

Sump Pump Failure

• A sump pump, accompanied by a sump pit and discharge pipe, collects water form the weeping tiles around the basement and pumps the water away from the structure. If the sump pump is not correctly and efficiently pumping, it may not prevent flooding as intended. The pit should be cleaned of debris regularly, the screen on the pump should be cleaned and the discharge pip should be directing water away suitably. Sump pumps generally use electric power, which may be unavailable during blackouts. In this case, a battery-powered backup sump pump will prove extremely useful.

Natural Flooding Disasters

• Natural flooding of rivers, streams or other bodies of water may cause basement flooding. Floodwater may also contribute to groundwater, which can seep in the basement. This type of flooding may be the most sporadic and damaging and can be more difficult to predict and prevent than other types of flooding. If an area is prone to flooding or development has altered water flow, obtaining flood-specific insurance may be a cost-efficient and practical approach.