If you searched French drains and landed on a national how-to page, most of what you read was written around breaking up a basement floor. None of that applies here. Northeast Florida homes are slab-on-grade. There is no basement perimeter to jackhammer, no interior sump pit, no finished lower level to protect.
What we actually get called for is different: a side yard that stays soft for three days after a storm, a back corner that grows moss instead of grass, water sheeting toward the slab off a neighbor’s lot, and sod that keeps dying in the same low spot no matter how many pallets go down.
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This is how that work actually gets built in Duval, St. Johns and Clay counties, and why sand of all things holds water.
The basement problem. Most top-ranking French drain articles split their advice into exterior and interior systems, and the interior half is written around cutting a channel through a basement floor and setting a sump pit. If you are reading one of those articles in Jacksonville, about half of it does not apply to your house. Everything below is exterior only.
How a French drain is actually built
A French drain is a simple idea held to tight tolerances. Every element below exists to keep sand out of the stone, because the day fines fill the voids is the day the trench stops draining.
- Excavation and depth. Most residential runs sit 18 to 24 inches deep, deeper for curtain drains intercepting off-site flow. Depth is set by where the water actually sits and how much fall is available to the outlet.
- Filter fabric, wrapped rather than laid. Non-woven geotextile lines the trench and folds back over the top of the stone so the aggregate is fully enclosed. A strip in the bottom is not a wrap, and the wrap is the only thing keeping sand out.
- Washed stone, never fines. Screenings and crusher run look like the same gray rock in the yard and behave nothing like it: the dust packs, the voids close, and the trench loses the space that moved water.
- Perforated pipe, bedded and oriented. Rigid perforated pipe set on a bed of stone with the perforations facing down, so water enters at the lowest point and the pipe empties rather than holding a column.
- Consistent fall, end to end. Continuous slope to the outlet, on the order of one percent, with no bellies or back-pitch. On a flat lot that fall is built into the trench and checked with a laser, because one low spot becomes a silt trap.
- The outlet, decided before the first shovel. Solid, non-perforated pipe carries flow from the stone to a daylight point, a stormwater structure or a dry well. Water released back into the ground it just left is not drainage.
What to look for in a drainage proposal
Two proposals for the same yard can describe completely different systems, and the difference is invisible from the driveway. It shows up years later, when one silts shut. Compare written specifications item for item.
| Spec item | What the proposal should say | Why it matters |
|---|---|---|
| Stone | Clean washed angular stone, named by size | Screenings and fines pack the voids and end the trench |
| Filter fabric | Non-woven geotextile wrapped around the stone | A strip laid underneath leaves three sides open to sand |
| Pipe | Rigid perforated pipe, plus solid pipe to the outlet | Sock-wrapped flex pipe is where sand collects |
| Depth and fall | Trench depth and continuous slope, stated as figures | Depth chases the water, slope keeps the line clean |
| Outlet destination | The specific place the water discharges, named | An unnamed outlet means the hardest part is unsolved |
| Restoration | Backfill in lifts, compaction, sod or hardscape put back | Settlement seams are the usual complaint after a dig |
| Irrigation | Who repairs cut lines and when the zones are tested | Irrigation gets hit; unassigned, the repair becomes yours |
On paper the difference becomes legible: one contractor is wrapping washed stone and daylighting to a swale, the other is dropping sock pipe in a sand trench with no stated outlet.
Why sandy soil still floods
Homeowners are genuinely surprised by this one. Jacksonville sits on sand, sand drains, so why is the yard holding water?
Three reasons, and usually all three at once.
The water table is close.
Across much of Duval and eastern St. Johns County, the seasonal high water table sits within a couple of feet of the surface during the summer wet season. Sand only drains if there is somewhere below it for the water to go. When the ground is already saturated from below, the surface has nowhere to push water down to.
There is often a hardpan under the sand.
Northeast Florida flatwoods soils frequently carry a dark, cemented layer a foot or two down, where organic material and iron have bonded the sand grains together. Water moves briskly through the loose sand above it and then stops cold. You get a perched layer of water sitting on a hard shelf, which is why a yard can be soupy on top and bone dry three feet down.
The lot was graded for the builder, not for you.
Production grading gets water off the pad and toward the street. It does not account for the pool deck you added, the shed pad, the raised bed along the fence, or the fill the neighbor brought in. Any one of those can dam a flow path that used to work.
This is also why “just add more sod” never fixes it. Sod is not a drainage system, and laying it into the same low spot every eighteen months is a losing fight against a grade that will not correct itself.
What actually drives the scope of the work
- Length of run. The largest single factor, and the one you can estimate yourself by pacing the wet area.
- Depth. Deeper trenches are slower to cut, and depth is dictated by where the water sits and where the outlet is.
- Where the water goes. A yard that falls toward a swale, ditch or retention pond is the straightforward version. A flat lot with no outlet needs a dry well or a pump, and the design gets considerably more involved.
- Access. If a mini excavator can reach the work, the trench opens in hours. If the only way in is a 36 inch gate, the same run is dug by hand and takes far longer.
- What is already in the ground. Irrigation lines, invisible fence, low voltage lighting, roots and utilities all slow the dig. Irrigation almost always needs repair afterward, and that has to be planned rather than discovered.
- Restoration. Sod, pavers, mulch and plant replacement are part of the job, not an afterthought. A drain through a finished landscape is a bigger undertaking than the same drain through bare turf.
- HOA and community stormwater rules. Many Jacksonville and St. Johns County communities have rules about where water may be discharged, particularly near retention ponds and common areas. Worth confirming before design, because it can change the outlet and therefore the whole layout.
On discharge. You cannot simply move your water problem onto the lot next door. Practically, that means the outlet has to go somewhere legitimate: the street, a swale, a stormwater structure, or a dry well on your own property. Where a good outlet does not exist, that constraint drives the design more than anything else. We work this out during the site visit, and anything that requires approval is worth confirming with your county or HOA directly.
When a French drain is the wrong answer
We would rather tell you this before the trench is open than after.
- The water is only near the house and only after a hard rain. Check gutters and downspouts first. Downspouts dumping at the foundation cause an enormous share of “drainage problems,” and burying downspout lines out to a pop-up is a far smaller job than a French drain.
- The problem is one shallow low spot. Regrading that area is often simpler and more durable than piping it.
- Water is pooling on a deck or hard surface, not in the yard. That is a surface pitch and board spacing issue rather than a subsurface one. We covered that separately in why water pools on decks after rain.
- The yard sits in a genuine flood zone. Drainage work manages rainfall on your lot. It does not solve base flood elevation, and anything you build there has its own requirements. See building in a Jacksonville flood zone.
- There is a grade change worth holding. Sometimes the right fix is structural rather than buried. Our post on retaining wall installation in Clay County covers where that makes sense, and we routinely integrate drains, swales and basins into wall projects.
Drainage options compared
| Option | Best for | Weakness |
|---|---|---|
| Regrading and swale | Broad shallow low areas with somewhere to fall | Needs room and a destination |
| French drain | Saturated ground, perched water, long wet strips | Needs an outlet, can silt over time |
| Catch basins and pipe | Defined puddles and hard surface runoff | Only collects where you place them |
| Curtain drain | Water arriving from uphill or off-site | Longer runs, more excavation to reach the flow |
| Dry well | Lots with no legal outlet | Limited volume, poor choice in a high water table |
| Downspout burial | Roof water at the foundation | Does nothing for yard-wide saturation |
How long it lasts, and what shortens it
A properly built French drain, meaning washed stone rather than fines, real filter fabric, and consistent fall, should give you 20 to 30 years. The ones that fail early almost always share the same three shortcuts: no fabric or the wrong fabric, dirty stone with sand mixed through it, and a flat run with no slope. Sand is the enemy here. Northeast Florida soil will migrate into a poorly wrapped drain and choke it in a handful of years.
Keeping basins clear of leaves and checking the outlet after storm season covers most of the maintenance.
Frequently asked questions
How long does a French drain take to install?
Do I need a permit for drainage work in Jacksonville?
What are the alternatives to a French drain?
What are the downsides of a French drain?
Where should a French drain not go?
How deep is a French drain usually buried?
My French drain is full of dirt. How do I clear it?
What is the lifespan of a French drain?
Get a real plan for your yard
Drainage does not survive being diagnosed over the phone. The outlet, the depth, the access and whatever is already buried out there decide the design, and all four need eyes on them.
We will walk the lot after a rain if that helps, tell you honestly whether you need a full system or a downspout fix, and put a written spec against it. Drainage work ties into our hardscaping services and our landscaping and yard grading, so if the fix touches a patio, wall or sod, it gets handled as one project rather than three.
Written By:
Coastal Outdoor Construction
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