Atlanta is a city in the trees, which is a charming way of saying we live in a rainforest. We get more annual rainfall than Seattle. And in fifteen years of designing houses here, the thing that has undone more good exterior work than bad taste, bad budgets, or bad contractors is water going somewhere nobody planned for it to go.
Nobody hires a designer to talk about drainage. But I have watched a client spend real money on boxwoods, a bluestone walk, and a fresh coat of paint on the trim, and then watched all three fail in eighteen months because the grade sent every storm straight back at the house. Drainage is not a landscaping afterthought. It is the substructure the entire exterior sits on, and a French drain is the most common piece of it. Here is what actually goes wrong with them, and how to tell when yours has quit.
What a French drain is doing under there
A French drain is a perforated pipe laid in a gravel bed and wrapped in landscape fabric. Water finds the gravel, enters the pipe through the perforations, and gravity carries it somewhere useful and away from your foundation. That is the whole idea. It is a simple system, which is why when it fails it usually fails for a simple reason.
The warning signs are visible from the yard, and most of them are aesthetic before they are structural:
- Water pooling near the foundation or standing in the yard hours after rain has stopped
- Drainage that has gotten noticeably slower than it used to be
- Soggy patches in beds, or a stripe of lawn that stays a different green than the rest
- Mulch that migrates, or bed edging that keeps shifting out of line
- Paint blistering or peeling on siding and trim within a foot or so of grade
That last one is the tell most people miss. When the bottom band of your exterior paint fails and the rest of the wall is fine, the problem is almost never the paint.
Why French drains stop working
Debris and sediment
Leaves and silt wash in over the years and pack the gravel bed and the pipe. This is the most common cause and the least dramatic. It happens gradually enough that most people adjust to the pooling rather than notice it.
Root intrusion
In a canopy city this is the one to watch. Roots find perforated pipe because perforated pipe is exactly where the water is. Anything you plant near the run should be chosen with that in mind, which is a design decision as much as a horticultural one.
Slope problems
A French drain needs roughly a one percent fall to work at all. If it was installed flat, or if the soil has settled since, water sits in the pipe instead of moving through it. Settling is common on new construction and on any yard that has been regraded.
Crushed or cracked pipe
Vehicles, heavy equipment during a renovation, or simple age. A collapsed section will back the whole run up behind it.
Repairing it
Find the run and look at it. Locate both ends, then walk the line after a heavy rain. Where the water is pooling tells you roughly where the blockage is.
Flush the pipe. For sediment, a hose at pressure or a drain snake will often clear it. Go gently. It is easy to punch through old corrugated pipe and turn a clog into a break.
Replace what is damaged. Cracked and crushed sections have to come out. This means excavating that stretch, which is the point at which you should think about what goes back on top of it, because you are going to be replanting anyway.
Correct the slope. If the fall is wrong, clearing the pipe only buys you a season. Re-laying the affected run with proper pitch is the actual repair.
Test it. Run water through and confirm it exits where it is supposed to. Then confirm where that is. I have seen a drain faithfully deliver every storm to the base of a neighbor's retaining wall for a decade.
The design part
Once the system works, the excavation is an opportunity rather than a scar. A drain run is usually a straight line through a bed, which is exactly where you would want structure anyway.
Gravel and river stone can stay exposed as a dry creek, which reads as intentional instead of remedial and gives you a texture change most yards do not have. A discreet channel drain in a terrace or at a garage apron disappears once it is set flush and the surrounding material is chosen to match. And planting over a repaired run wants shallow, fibrous root systems rather than anything that will go looking for the pipe. Ferns, liriope, hellebores, low grasses. In Atlanta all four of those want the shade we already have.
The broader point is the one I make about curb appeal generally: the exterior of a house is a design problem with a maintenance schedule attached, and the parts nobody sees determine how long the parts everybody sees will last. The same logic applies to outdoor rooms. A beautifully furnished terrace that holds water after every storm is a terrace you will not sit on.
Keeping it working
- Keep gutters and downspouts clear. Most of what clogs a French drain arrives from the roof.
- Walk the run after heavy rain twice a year. It takes ten minutes and it is the entire early warning system.
- Be deliberate about what you plant near it, and move anything aggressive before it becomes a repair.
- Check the outfall. Blocked exits are as common as blocked pipe and much easier to fix.
None of this is glamorous. But water is the one force that will quietly dismantle every exterior decision you have made, and a working drain is what buys those decisions the twenty years they were meant to last.
