Common Basement Drainage Types

Above-Slab Drainage

• When it comes to water drainage problems in the basement, the installation of an above-slab drainage channel is the most cost effective and least invasive approach. The method is most effective in basements that have concrete walls and foundations that contain cracks. The channel connects to the cement floor slab at the base of each exterior wall. As water gathers, it runs along the channel and into the basement's sump pump.

Slab Edge Channel

• The slab edge channel follows the same concept as the above-slab channel, except that the channel is within the cement floor slab instead of above it. During installation, sections of the cement floor slab require removal along the edges of each exterior wall. The installer places drainage pipes inside the new gap between the slab and walls. The drainage pipes carry water that enters the basement directly to the sump pump. A new, thinner layer of cement conceals the drain pipes after the installation.

Below Slab Drainage

• Installing a drainage channel below the original cement floor slab is a highly effective way of ensuring that all water drains below the basement floor. This method requires the complete removal of the cement floor slab along the slab edge. Drainage pipes are set in place within the perimeter footing with an aggregate poured over top. The drainage pipes guide water to the sump pump. Dimpled sheeting attaches to the lower edge of the exterior walls, guiding water to the drain pipes. The installer then replaces any concrete removed during the process.

Considerations

• Each drainage type has its pros and cons, requiring some consideration before the installation begins. While the above-slab method is the simplest, it can create moisture problems. Because it is impossible for this method to remove all of the water, some remains behind the walls, encouraging mold and mildew. The slab edge drainage method works best for masonry walls, but because drill holes allow moisture to permeate the block cores, the basement walls require the application of a vapor guard. A drainage system below the slab is highly effective but installers usually recommend a management system for active soil gasses, which adds to the cost of the drainage system.