Hillside and retaining wall drainage
Water is behind most failing walls and slipping slopes. Here's how drainage keeps both in place.
Wet soil is heavier and weaker than dry soil. Behind a wall it adds pressure; on a slope it can let the ground slide. With more than 43 inches of precipitation a year and its wettest months from May through July, Morgantown gives hillside drainage plenty to do.
Where is the water coming from?
- Downspouts dumping at the top of a slope or right behind a wall
- Street and driveway runoff flowing onto the lot
- Water from neighboring properties uphill
- Springs or seeps that come out of the hillside after rain
A contractor should trace the water before deciding on a fix.
What are the common fixes?
- Base drain. A perforated pipe at the bottom of a wall, in clean stone, carried out to daylight or a storm line.
- Stone backfill and fabric. Gravel behind the wall, separated from the soil by filter fabric so it doesn't clog.
- Curtain or French drain. A gravel trench above the wall that catches water moving down through the soil.
- Swales and grading. Shallow channels that steer surface runoff around the wall instead of over it.
- Downspout lines. Solid pipe that carries roof water past the wall and slope.
Signs of a drainage problem
- Water running out of the base or face of a wall after rain
- Soggy ground behind a wall that stays wet for days
- Muddy staining down the wall face
- New wet spots or seeps on a slope
Where can the water go?
It has to end up somewhere that doesn't cause a new problem, like a neighbor's yard or the slope below. On tight city lots, that may mean a storm connection, which can involve the city. Ask your contractor where the outlet will be.
The contractor sets the price after seeing the slope, the soil, how equipment can reach the spot and what the wall has to hold back. We don't quote prices, and any figure you hear over the phone before someone has walked the site is a rough guess at best.
Where we connect you with help
Common questions
Can drainage be added behind a wall that's already built?
Sometimes, by digging behind it or adding a curtain drain above it. If the wall is already leaning, rebuilding it with drainage is often the better fix.
Why is my yard wet above the retaining wall?
Water is collecting there faster than it drains. Common causes are downspouts, runoff from uphill, clay soil and a wall with no drain.
Related services
More background: Morgantown retaining wall guide.
Wall bowing out, or the hillside behind it slipping?
Call now and a local retaining wall contractor will come look at it and quote the fix.