Repairing a Compromised Footer Drainage System

This home is in a zero-lot-line neighborhood.  The East wall of the house abuts the neighbors’ driveway and is roughly two feet below grade. Because the driveway was extended, a larger volume of water was directed toward this wall and quickly became a recipe for disaster.

The existing liquid rubber membrane was deteriorating due to the intrusion of roots, which eventually allowed water to enter the house.  The drain was also clogged with sediment as there was no filter fabric encapsulating the drainage stone, or the pipe itself.

Normally the water would filter through the stone and infiltrate the pipe, but the roots from the plants and years of silt and sediment had slowed the process enough that the water would sit against the wall.  Once the plant roots broke through the membrane, all the water in the soil seeped into the house.

The damage to the house consisted of rotted sill plates, wall studs, and a considerable amount of soggy carpet.  A large storm was all it took for catastrophic failure and the home was suddenly a mess with water and smelly mold.

Instead of replacing what was originally there, the system was completely redesigned.  PVC pipe was used for durability and ease of maintenance.  Two clean-outs were added so that future homeowners could easily flush the drain with a garden hose.

The drain trench was lined with filter fabric and the pipe itself was also wrapped.  Utilizing fabric slows the process of “blinding off”, which is the inevitable accumulation of fine silts and sand particles against the drainage surface.  These particles build up over time and block or “blind” the drain which prevents water from flowing freely into the system.  This essential step was absent from the initial design, which is why the pipe was almost completely filled with soil and debris.

As a final step to retard water entry into the masonry, the east wall was cleaned and re-coated with liquid rubber.  The wall was cleaned with an angle grinder with a wire wheel so that all loose material was removed.  Pressure washing removed any remaining material and soil and the wall was allowed to dry.  Two coats of Ames Liquid Rubber were applied with a sheet of 6 mil plastic between coats for reinforcement.  The filter fabric was also embedded into the final coat to prevent the angular stone from puncturing the membrane over time.

Finally, with everything prepped, the drain and fabric were placed, pitched to 1% slope, and back-filled with #57 crushed stone.  The fabric used was SRW NW 4.5, which provides adequate encapsulation, but is permeable to allow water infiltration.

As a final touch, the exit for the drain was fabricated and encorporated into the existing stone bed-border along the front of the house.  Because of the tight budget, a spillway was not installed, but some effort was put forth to make it look as nice as possible. To prevent rodents, insects, spiders, and debris from entering the outlet end of the drain a screen was secured with a Fernco fitting and ring clamps.




Category(s): Project Archive

4 Responses to Repairing a Compromised Footer Drainage System

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