During a heavy rainstorm (without lightning), grab an umbrella and go outside. Walk around your house and look around at the roof and property. A rainstorm is the perfect time to see how the roof, downspouts and grading are performing. Observe the drainage patterns of your entire property as well as the property of your neighbour. The ground around your house should slope away from all sides. Downspouts, surface gutters and drains should be directing water away from the foundation.
1) Poor Drainage – Most problems with moisture in basements and crawlspaces are caused by poor site drainage. The ground should slope away from window wells, outside basement stairs, and other means of egress. Your job is to monitor and maintain the drains and piping. Drains and piping should be open and clear of leaves, earth and debris. A garden hose can be used to check water flow, although its discharge cannot approximate storm conditions.
2) Planters – Check any planting beds adjacent to the foundation. They are built in a way that traps water. The structure around the planting beds act like a dam and traps water. Flower planters should never be installed up against a house’s exterior wall.
3) Hillside – Where a building is situated on a hillside, it is more difficult to slope the ground away from the building on all sides. On the high-ground side of the building, the slope of the ground toward the building could be interrupted by a surface drainage system that collects and disposes of rainwater runoff. Swales can be used to direct surface water away from the foundation. There are two general types of surface drainage systems: an open system consisting of a swale (often referred to as a ditch), sometimes with a culvert at its end to collect and channel water away; and a closed system, consisting of gutters with catch basins.
Puddles are not good. The ground surface beneath decks, porches and other parts of a building that are supported by posts or cantilevered structures should be checked. It should not have any low-lying areas but should be sloped so that water will not collect and puddle there. Settled backfill allows water to collect next to the foundation wall and penetrate the basement.
Downspouts need adjustment. Water from the roof reaches the ground through gutters and downspouts or by flowing directly off roof edges. Because downspouts create concentrated sources of water in the landscape, where they discharge is important. Downspouts should not discharge where water will flow directly on or over a walkway, driveway or stairs. The downspouts on a hillside building should discharge on the downhill side of the building. The force of the water leaving a downspout is sometimes great enough to damage the adjacent ground, so some protection grade, such as splash block or a paved drainage chute, is needed.
Water that flows directly off a roof lacking gutters and downspouts can cause damage below. Accordingly, some provision in the landscaping may be needed, such as a gravel bed or paved drainage way.
The sump pump should not recycle. When a sump pump is used to keep a building’s interior dry, this discharge should drain away from the building and should not add to the subsurface water condition that the sump pump is meant to control.
4) Naturally Wet – Look around the entire site for the presence of springs, standing water, saturated or boggy ground, a high water table, or dry creeks or other seasonal drainage ways, all of which may affect surface drainage.