Prefabricated Foundation Drainage System Installation

The product can be laid into preexisting trenches available from foundation construction or trenches constructed specifically for the drainage field. The width of the trench is typically 2–6 in wide. The depth of the trench is determined upon the actual site conditions and soil permeability. Figure 2.6 represents a typical drainage detail.

The prefabricated plastic drains usually permit the excavated soil to be used as back-fill, eliminating the requirement for special backfill material. The backfill must be mechanically compacted in layers.
Geotextile covering is selected based on the soil conditions. Here are the basic geotextiles required for typical soil conditions:

● High clay content—nonwoven needle-punched geotextile
● Sandy soils—woven materials with high permeability
● High silt content—small-opening geotextiles

Soils of any combinations of the above types generally require testing to be performed and specific recommendation by the drainage system manufacturer.

Manufacturer-provided tees, splicing connectors and outlet connectors should be used as designed. The system is designed to collect and drain water in a variety of ways that meet specific site requirements. Drainage can be as simple as outflow to bare soil away from the structure as surface drainage, or it can be designed to outflow into municipal storm drains.

FIGURE 2.6 Typical detailing for foundation drainage system.
(Courtesy of TC Mira DRI)