Basic Waterproofing for Basements
- Install and maintain gutters and downspouts so that they route all rainwater and snow melt far enough away from the foundation of the building to ensure that pooling does not occur near the walls of the structure. At least 10 feet from the building is best, and at the point where water leaves the downspout, it should be able to flow freely away from the foundation instead of back toward it, and should not be collecting in pools.
- The finish grade should be sloped away from the building for 10 to 15 feet. Low spots that may lead to water pooling should be evened out to prevent the possibility of standing water near the foundation.
- Shallow ditches called swales should be used in conditions where one or more sides of the building face an upward slope. A swale should slope away from the building for 10 to 15 feet, at which point it can empty into another swale that directs water around to the downhill-side of the building, leading it away from the foundation.
- Identify areas where water may be entering through cracks or holes by checking for moisture, leaking or discoloration. Every square inch of the basement should be examined, especially in cases where leaking or flooding has not been obvious, but moisture buildup is readily apparent.
- A mixture of epoxy and latex cement can be used to fill small hairline cracks and holes. This is a waterproof formula that can help ensure that moisture and water do not penetrate basement walls. It is effective primarily for very small cracks and holes.
- Any cracks larger than about 1/8-inch should be filled with mortar made from one part cement and two parts fine sand, with just enough water to make a fairly stiff mortar. It should be pressed firmly into all parts of the larger cracks and holes to be sure that no air bubbles or pockets remain. As long as water is not being forced through basement walls due to outside pressure, the application of mortar with a standard trowel will be sufficient if special care is taken to fill all cracks completely.
- If water is being forced through by outside pressure, a slightly different method of patching with mortar can be used. Surface areas of walls or floors with cracks should first be chiseled out a bit at the mouth of the crack and all along its length. Using a chipping chisel and hammer or a cold chisel, cut a dovetail groove along the mouth of each crack to be filled, and then apply the mortar thoroughly. The dovetail groove, once filled, should be strong enough to resist the force of pressure that was pushing water through the crack.