· by Michael Blair, Nashville's Landscapers
Standing water in a Middle Tennessee yard is common enough that people stop noticing it. It is worth noticing, because the difference between a wet corner and a foundation problem is often just time and volume.
Three different problems that look the same
Water arriving from uphill is a grading and interception problem, solved by a swale or a curtain drain across the slope. Water sitting where it fell is an infiltration problem, because the clay beneath will not take it.
Water appearing near the house after rain has usually come off the roof. Downspouts discharging within a few feet of a foundation put thousands of gallons a year exactly where you least want it.
Start with the cheapest fix
Extend the downspouts. Getting roof water six to ten feet away from the wall solves a surprising share of Nashville drainage complaints on its own, and it costs almost nothing to test with temporary extensions before committing.
Then check the grade against the foundation. You want a fall of roughly six inches over the first ten feet away from the house. Settled beds and built-up mulch commonly reverse that without anyone noticing.
When a French drain is the right answer
A French drain intercepts and moves subsurface water. It works when there is somewhere lower to take it, and it does nothing at all in a flat yard with no outfall — a pipe full of water with nowhere to go is just a buried reservoir.
On a genuinely flat Nashville lot, the honest options are a dry well sized for the volume, a pump system, or regrading to create fall. Anyone quoting a French drain without discussing where it daylights has not thought about it.
- Confirm there is a lower outfall before pricing a French drain
- Clean angular gravel, not rounded pea gravel
- Geotextile sock or wrap to stop silting
- Perforations down, contrary to intuition
- Cleanouts at the ends for maintenance
What clay means for any of it
Infiltration solutions such as rain gardens and dry wells work far more slowly here than in sandy soil, and they have to be sized for that. A dry well that would serve a house in Memphis sand may back up in Davidson County clay.
Percolation is worth testing rather than assuming. Dig a hole, fill it, and see how long it takes to drain. If it is still holding water the next day, any design that relies on the soil accepting water is the wrong design.