Jacksonville Drainage Specialists
Water Pooling on Your Lanai or Patio in Jacksonville: Why It Floods and How We Fix It
Water that sits on the lanai after every storm, creeps toward the sliding door or leaves a green line at the screen enclosure footer is almost never random. A slab poured flat, a downspout dumping beside the enclosure and a lawn above the patio edge trap rain with nowhere to go, while a high water table or hardpan keeps the ground from taking it. Owner Albert Urbank diagnoses where the water comes from and where it gets stuck on site before anything is quoted.
The short answer: Water pools on a lanai or patio because it has no fall to leave and no pipe to carry it away. The usual causes are a flat or back-pitched slab, a downspout dumping beside the lanai, a screen enclosure footer acting as a dam, a lawn higher than the slab, and clogged drains. The permanent fix is an NDS channel drain at the slab edge or footer, tied to FDM heavy-duty HDPE pipe running to a pop-up emitter, catch basin or dry well. Pool decks are the same problem; see our pool deck drainage page.
The 5 Causes of Lanai and Patio Flooding in Northeast Florida
1. The slab or paver field has no fall to the edge
A patio needs a steady fall away from the house toward an edge where water can leave. Many slabs are poured nearly flat, and some settle until they pitch back toward the house. Settled pavers develop the same birdbath dips. Rain that should run off in minutes lingers for hours, and water with no direction finds the lowest route, often the sliding door track.
2. A roof valley, scupper or downspout dumps beside the lanai
Jacksonville is sized for rain of about 9 inches per hour, and a roof valley or scupper gathers that into one rope of water. When the outlet lands beside the lanai, or on the enclosure footer, a small patio receives the runoff of a whole roof plane. Flexible recycled corrugated extensions from the home center crush, sag and clog, so the water ends up on the slab anyway. See downspout erosion for what that discharge does to the ground.
3. The screen enclosure footer and knee wall dam the slab edge
Screened lanais sit on a footer or low knee wall right where the slab would otherwise shed water. Water reaches the edge, cannot cross it and backs up. Mulch, pine straw and sand fill the small weep gaps, and the green algae line along the footer records how often it ponds. The aluminum framing at the base stays wet and corrodes sooner.
4. The yard is higher than the slab
New sod and years of mulch and pine straw raise a lawn an inch at a time, and nobody notices. The slab edge becomes the low spot and the lawn drains onto the patio. Across much of Northeast Florida a hardpan layer sits 12 to 36 inches down beneath sandy topsoil, so the sand saturates fast and sheds rain sideways toward whatever is lowest.
5. Deck drains or the paver base are clogged, or the water table is high
Many lanais have a deck drain that connects to nothing, or to a pipe packed with sand and roots. Paver bases clog the same way as joint sand washes out and weeds and roots take its place. Near the coast the water table is often within 24 to 48 inches of the surface, so the base stays saturated after a storm and pavers shift and heave.
The 20-Minute Diagnostic Walk
Narrow down the cause before anyone visits.
- Run a hose from the house side. Watch which way the water travels across the slab.
- Watch where the water stops. That spot, at the footer or a paver dip, is where the fix goes.
- Check the downspout outlets near the lanai. Look for washed mulch and flexible recycled corrugated extensions.
- Look along the footer line. Green stain or packed mulch means standing water.
- Check the yard grade. Lay a level or straight board from the slab edge across the lawn. A lawn at or above the slab is feeding the patio.
- Test the deck drains. Lift the grate and pour in a bucket of water. If it backs up, or vanishes with no sign of where, the drain leads nowhere.
How We Fix It
NDS channel drain at the slab edge or footer
This fixes causes 1 and 3. An NDS channel (trench) drain along the low edge or enclosure footer catches water across its whole width. It ties into FDM heavy-duty HDPE pipe, 3.5-inch or 4-inch, 100 percent virgin resin, rated for vehicle traffic, with snap-fit joints and no glue. There are no glued joints to crack as Florida soil swells and shrinks, and design life is 100-plus years. See channel drains.
Deck drains connected to real pipe
Existing drains only help if they lead somewhere. We trace and clear them, then connect each to solid (unslotted) HDPE running to an outfall.
Downspouts rerouted underground
For cause 2 we capture the downspout at its base and carry it away from the footer in solid HDPE to a pop-up emitter, catch basin or dry well, never a flexible recycled corrugated extension. See underground downspout drains and dry wells for sites with no outfall.
French drain just outside the footer
When the lawn is the source (cause 4), a slotted eight-slot HDPE French drain set just outside the footer intercepts the water before it reaches the slab.
Limited regrading at the lawn edge
Where the lawn has crept above the slab, we lower the strip beside the patio so the surface falls away.
The honest trade-off
Adding a drain means opening the surface. Pavers can be lifted and re-laid over the drain, the easier case. Poured concrete needs a saw cut and a patch, which is visible if you look for it. Both are routine. If a slab is pitched so badly that a drain cannot catch the water, we say so first.
What the Fix Costs
A French drain runs $2,500 to $6,500 for most Jacksonville yards ($25 to $60 per linear foot). Channel drains, buried downspout lines, catch basins, emitters and dry wells are priced per foot on our drainage cost page. Permit questions are on our drainage permits page.
Find out where your lanai water is coming from
Albert Urbank runs the hose test, checks the footer and grade, and shows you what traps the water, free.
Get a Free QuoteWhere Lanai and Patio Flooding Hits Hardest in Northeast Florida
Nocatee and Ponte Vedra
Screened lanais on nearly every home and a high water table keep footers wet. See drainage in Nocatee and Ponte Vedra.
St. Johns and Julington Creek
Paver patios on new fill settle and develop low spots. See drainage in St. Johns and Julington Creek.
Fleming Island
Pool homes under pine see needles clog deck drains. See drainage in Fleming Island.
Mandarin
Large patios under live oaks collect leaf litter, and roots invade old drain lines. See Mandarin.
Jacksonville Beach and Atlantic Beach
Sand and a shallow water table keep paver bases saturated. See Jacksonville Beach and Atlantic Beach.
Lanai and Patio Flooding FAQ
Why does water pool on my lanai when it rains?
Because the slab has no fall to the edge, or the edge is blocked. Usual causes are a slab poured flat or pitched back toward the house, a downspout dumping beside the lanai, a screen enclosure footer that dams the edge, a lawn higher than the slab, or deck drains that connect to nothing. A hose test shows which.
How do I stop water from coming in my sliding glass door?
Stop the water before it reaches the threshold, because caulk only treats the symptom. We find the source, then intercept the water with an NDS channel drain set out from the door, piped away in FDM heavy-duty HDPE, and fix the downspout or grade feeding it.
Can you add a drain to an existing lanai or patio?
Yes, and it is routine. On poured concrete we saw-cut a narrow trench, set the drain and pipe, and patch the slab. On pavers we lift the section, install the drain, and re-lay the same pavers. Either way it ties to buried HDPE pipe running to an emitter, catch basin or dry well.
Do channel drains work with pavers?
Yes. Pavers are lifted over the drain line, the NDS channel drain is set on a compacted base with the grate flush to the surface, and the pavers are cut to meet it and re-laid. Pavers open and close more easily than poured concrete.
Why does water collect at my screen enclosure footer?
The footer and knee wall sit right at the slab edge and act as a small dam. Water cannot cross it, so it backs up and leaves a green algae line, and mulch and sand fill the weep gaps. A channel drain along the footer, or a French drain just outside it, gives the water somewhere to go.
Will a French drain stop my patio from flooding?
It will when the water comes from the lawn. A French drain just outside the footer intercepts the runoff before it reaches the slab. It will not fix a flat or back-pitched slab, or a downspout dumping beside the lanai. Those need a channel drain or buried downspout line.
How much does it cost to fix lanai drainage?
A French drain runs $2,500 to $6,500 for most Jacksonville yards ($25 to $60 per linear foot). Channel drains, downspout lines, catch basins and dry wells are priced per foot on our drainage cost page. Albert quotes after an on-site diagnosis.
Quick Answers
Water on your lanai or patio?
Where the water comes from and where it gets stuck takes a hose and a level, not a guess. Albert Urbank diagnoses it on site, free, and the written itemized quote is the price the job is installed at.
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