Drainage behind retaining walls
Most failing walls around here have the same root problem: wet clay with no way to drain.
Clay that's soaked weighs more and pushes harder than the same clay when it's dry. Johnson City averages about 45 inches of precipitation a year, and the slow-draining soils in the valley hold onto it. A wall with no drainage path ends up holding back both soil and water.
What does working drainage include?
- A zone of clean crushed stone right behind the wall instead of the clay that came out of the hole
- A perforated drain pipe at the base, run to daylight or an approved outlet
- Filter fabric between the clay and the stone so the stone doesn't clog
- Weep holes in mortared and concrete walls
- A swale, curb or surface drain above the wall to catch runoff before it soaks in
- Downspouts and driveway runoff routed away from the top of the wall
Signs the drainage isn't working
- Muddy water seeping out of joints or the base days after rain
- Soggy, spongy ground behind the wall
- Moss, algae or soil stains spreading across the face
- A drain outlet that never runs, or one buried in mulch or soil
- A wall that leans a little more each wet season
Can drainage be added to a wall that's already built?
Sometimes. If the wall is still straight, a builder may be able to dig along the back, add stone and a drain, or intercept water higher on the slope. If it's already leaning, rebuilding the section with drainage built in is usually the better buy.
Where does the water go?
Water from a wall drain can't just be dumped onto a neighbor's lot. Ask the builder where the outlet will be and whether it ties into anything on the street. Inside city limits, Johnson City Public Works handles stormwater, so check with them before tying into a storm drain.
We don't quote prices. The builder sets a price only after seeing the slope, the soil and what sits above the wall, and anything said over the phone before that visit is a rough guess at best.
Where we connect you with help
Common questions
Why is my retaining wall wet all the time?
Water is collecting behind it. The wall may have no drain, the drain may be clogged or crushed, or runoff from a roof or driveway is soaking the backfill.
Do gutters really matter for a retaining wall?
Yes. A downspout that empties above a wall can put a roof's worth of rain straight into the backfill. Route it away.
Related services
More background: Johnson City retaining wall guide.
Wall bowing out, timbers rotting or water pouring through the face?
Call and a local retaining wall builder will come look at it and give you a quote.