Drainage behind retaining walls
Ask a Kingsport wall contractor why most walls fail and you'll hear the same answer: wet clay and nowhere for the water to go.
Soak a clay bank and it gains weight and leans on the wall with more force than it ever does in a dry August. Kingsport averages about 45 inches of precipitation a year, and clay subsoils weathered from the local limestone and dolomite let it through slowly. A wall without a drainage path ends up holding back a wet, heavy mass instead of just dirt.
What does a working drainage setup include?
- A band of clean crushed stone directly behind the wall in place of the clay that came out of the trench
- A perforated pipe at the base that runs to daylight or an approved outlet
- Filter fabric separating the clay from the stone so fines don't clog it
- Weep holes through mortared stone and concrete walls
- A shallow ditch or inlet uphill that grabs surface water before it reaches the backfill
- Downspouts and driveway runoff steered away from the top of the wall
How do you know it isn't working?
- Muddy water still trickling from joints or the base days after a storm
- Spongy, soggy ground along the back of the wall
- Moss, algae or brown soil stains spreading on the face
- A pipe end that stays dry after storms, or that nobody can find anymore
- Lean that grows by a fraction each spring
Can drainage be added to an existing wall?
Sometimes. If the wall is still straight, a contractor may be able to excavate along the back and add stone and a drain, or intercept water farther up the slope. If it's already leaning, rebuilding that section with drainage built in is usually the better use of your money.
Where should the water end up?
A wall drain shouldn't be aimed at a neighbor's yard. Find out exactly where the pipe will discharge and whether any of it ties into a street gutter or inlet. Kingsport lists grading among the work that needs a city permit, and Sullivan County names stormwater management among the permits a project there may need, so if the job involves regrading the slope or tying into a storm drain, the contractor should check first.
We don't give prices. A contractor can only price a wall honestly after walking the slope, seeing how a machine gets in and learning what the wall has to hold up, so treat any phone figure as a ballpark at most.
Where we connect you with help
Common questions
Why is water always seeping from my retaining wall?
Water is building up behind it. There may be no drain, the drain may be crushed or clogged, or runoff from the roof or driveway is soaking the backfill.
Do gutters matter for a retaining wall?
A lot. A downspout that empties above a wall sends a whole roof's worth of rain into the backfill. Pipe it somewhere else.
Related services
More background: Kingsport retaining wall guide.
Blocks creeping forward or an old tie wall going soft?
Call and a Kingsport-area retaining wall contractor will come out, look at it and quote the job.