Drainage and Waterproofing St. Armands Key
Foundation Masters provides homeowners, condominium boards and commercial property managers on St. Armands Key with engineer designed solutions to stop flooding, water intrusion, hydrostatic pressure and soil erosion.
This island does not drain by gravity. It drains by five stormwater pump stations. In July 2026 a faulty sensor kept one of them from starting, four ran instead of five, and a restaurant on the Circle measured ten inches of water in ten minutes.
We are a licensed Florida engineering firm and a repair contractor in the same company, and we were the first engineering firm to pioneer the waterproofing industry in Florida. Qualifying work carries a lifetime transferable warranty.
Contractor Execution With Engineering Behind It
Foundation Masters is a licensed Florida engineering firm, CA# 30969, and a structural repair contractor. St. Armands is an unusual market for us because so much of it is commercial: the retail, restaurant and gallery property around the Circle, the condominium and association buildings, and the single family homes on the residential streets and the canal and bayfront lots radiating out from it.
The work is usually water entering at the ground floor of a commercial unit, moisture coming up through a slab, hydrostatic pressure against below grade concrete, salt driven spalling on structural concrete, material washing out from under paving and slabs, and the recovery work that follows an event, which on this island has been a recurring rather than occasional requirement.
A commercial tenancy changes what a good answer looks like. A restaurant cannot close for a month while somebody experiments. Scope, sequence, duration and what happens the next time it rains all have to be settled before work starts. We pair contractor work with in house civil engineering, geotechnical engineering in Sarasota and soil borings, so the design and the installation answer to the same firm.
A licensed Florida professional engineer signs and seals the drawings. Inspections are free.
Signs You Need Drainage and Waterproofing on St. Armands Key
- Water reaching a doorway or a ground floor unit during ordinary storms
- Standing water that clears slowly after rain or a high tide
- Buckled wood floors or tile popping from slab moisture
- Water stains or efflorescence along baseboards and block walls
- Mildew odor or visible mold at floor level
- Salt staining, rust staining or spalling on concrete near grade
- Paving, walkways or slab edges that have gone hollow or dropped
- Parking or service areas that drain slowly after rain
- Ground dropping behind a seawall cap on the bay side
The first one is the St. Armands call. It is worth taking seriously the first time it happens, because on this island the interval between ordinary storms that reach a doorway and events that fill a unit has been getting shorter.
Five Pumps. In July, Four Were Running.
Most of the pages on this site have to explain to owners why their drainage depends on something outside their property line. On St. Armands Key there is no need to explain it, because the island demonstrated it in public, on an ordinary Thursday night, in July 2026.
Start with the arrangement itself. St. Armands does not drain downhill to somewhere lower, because there is no somewhere lower. It drains because five stormwater pump stations on the Circle push water out into the bay. That is what it takes to keep a commercial district dry on a barrier island, and most people who shop and eat there have no idea it exists.
On 24 July 2026, during a storm rather than a hurricane, a faulty sensor kept one of those five pump stations from turning on. The director of the Sarasota County Stormwater Department, Ben Quartermaine, put it plainly: only four of the five pump stations were draining water into the bay. A restaurant manager on the Circle described what that looked like from a doorway. In ten minutes it was about ten inches.
The county fixed the sensor, and it should be said that they responded quickly. But sit with what the event actually proves. A public drainage system operating at eighty percent, on a night with no hurricane in it, put ten inches of water in a commercial doorway in ten minutes. That is not a criticism of anybody. It is a measurement of how little margin this island has.
The 2024 season had already made the same point three times over. St. Armands Circle flooded three times during the 2024 hurricane season, and Helene and Milton brought several feet of water through it, forcing nearly every business to close for weeks and in some cases months. The City Engineer has described the system as overwhelmed, and county officials have said directly that larger and more frequent storms have exceeded what it was built to handle.
None of that is hidden and none of it is disputed. It is the published, on the record condition of the island, and it leads somewhere specific for anybody who owns or leases a building here.
Surface Water
Grade, collection and conveyance. The Florida Building Code requires the ground to fall six inches within the first ten feet from the foundation, and two percent on impervious surfaces. In a dense commercial setting there is often nowhere for that fall to go, which is why the entrance detail matters so much.
Water Already Under the Slab
Hydrostatic pressure and capillary movement through porous concrete. Surface drainage never reaches it, and on a barrier island the water arriving at the slab is brackish, which brings chlorides to the reinforcing steel as well.
A System With Moving Parts
The condition specific to St. Armands. Pumped drainage is not passive. It has sensors, controls, power and maintenance intervals, and a system with moving parts has failure modes that a ditch does not.
Everything That Failed in July Was Outside Your Property Line
The pump was not yours. The sensor was not yours. The decision about how many pump stations the Circle has, and the schedule on which they are maintained, is not yours either. And yet the water that came through the door was very much your problem.
That is the whole argument on this island, and it is not a pitch, it is arithmetic. Everything upstream of your threshold is somebody else, and the record for the last two years is that it does not always work. The only portion of the system you control is the portion inside your own property line: your grade, your entrance detail, your slab, your below grade concrete and whether anything sits between it and the ground.
Real work is being done and it deserves saying. Sarasota County approved 13.5 million dollars in December through the Resilient SRQ program to upgrade drainage on St. Armands, with improvements expected by the end of 2027. The plans discussed publicly include pump station upgrades, underground stormwater vaults, permeable pavement, additional drainage and removable flood barriers of the kind deployed at Tampa General Hospital.
Two honest observations about that. The first is the timeline: end of 2027 is several wet seasons away, and the island has flooded in each of the last several. The second comes from the City Engineer rather than from us, and it is the more important one. Those measures are aimed at mitigating the impact of heavy rain events, not necessarily storm surge. Rain and surge are different problems, and a fix for one is not automatically a fix for the other.
So the sensible position for an owner here is not to wait and not to panic. It is to make the part you control as good as it can be, on the assumption that the part you do not control will sometimes be at its limit. That means sealing the structure rather than relying on a system with moving parts in it. Borings where the question is what is under the slab and how much has already moved.
City Permits, County Pumps
St. Armands Key sits inside the City of Sarasota, so permitting, inspection and floodplain administration for property here run through the City rather than through the county. That distinguishes it from Siesta Key and Casey Key, most of which are unincorporated county, and it is worth knowing because advice moves between these islands freely and does not always survive the trip.
The stormwater side is different again. The pump and drain system serving the Circle is managed by Sarasota County, and the resiliency funding has come through the county program. So a property here can have a City permit, a City inspection and a County drainage system, which is a perfectly normal arrangement and a reliable source of confusion when something goes wrong.
On the flood side, in a mapped flood hazard area the lowest floor has to be at or above base flood elevation plus one foot, with certification at lowest floor placement and again at final inspection. Whether an existing structure gets pulled into that turns on a substantial improvement or substantial damage determination, and the threshold is 50 percent of the market value of the structure alone, not the land. After an event that damages a commercial building on this island, that determination is frequently the single most consequential number in the project.
One correction while we are here, because it is on a great many pages about this coast and it was on the previous version of this one. There is no Florida rule that a finished floor slab must be twelve inches above grade. The code requires the six inch fall in ten feet described above, and a foundation drain only where a foundation both retains earth and encloses habitable or usable space below grade, which a Florida slab on grade building never does. Minimum elevations come from the flood map and the flood ordinance instead.
Check your zone through the FEMA Flood Map Service Center, and take anything that turns on a determination to the City of Sarasota and to counsel.
Rate Against Capacity
Pages about this coast routinely quote 50 to 60 inches a year. The nearest well documented long records run below that: the Bradenton normal for 1991 to 2020 is 56.28 inches and the Tampa normal is 49.48 inches. Quoting the top of a range as the average inflates every number that follows from it.
You will also see three inches of rain in an hour described as an ordinary summer storm. It is not. That is close to the peak rate in events the National Weather Service treats as extremely rare.
On St. Armands the number that decides outcomes is neither of those. It is the rate of arrival measured against the capacity of the collection system, and that has been stated locally in very plain terms: the number of street drains on St. Armands is inadequate, and in recent rainfall the water was coming down at too fast a rate for the number of drains available to take it.
That is a capacity problem rather than a weather problem, and it is why the ten inches in ten minutes figure from July is more informative than any annual average could be.
What the Work Actually Is
Foundation Masters developed the first true engineered waterproofing system in Florida to solve these issues. The process is four steps and it does not vary much.
- Excavating a trench to roughly 12 inches below the slab edge to expose the footer and wall
- Applying the Seal Tight Waterproofing System to protect below grade concrete and footings, including in salt exposed soils
- Designing engineered drainage piping or sump discharge to move water away from the foundation and prevent undermining of sandy soils
- Installing gutters and grading corrections to keep stormwater away from the slab edge
The second step is the one that matters most on this island, because it is the only part of the system whose performance does not depend on a pump, a sensor or a county maintenance schedule. Waterproofing keeps water out of the concrete regardless of how much of it is standing outside. Alongside it we handle threshold and entrance detailing on commercial units, subgrade stabilization and void filling, catch basin and storm pipe repair, vapor retarder work under new slabs, and seawall repair and permitting on the bay side.
What we will not tell you is that any of this makes a building immune to surge. It does not, and anybody who says otherwise is selling something. What it does is stop the water that arrives in ordinary weather, protect the concrete and the reinforcement from what does arrive, and remove the slow damage that runs between events.
Retail on a Barrier Island Is a Different Problem
Very few places in Florida put dense, high value retail and restaurant space directly on a barrier island. St. Armands does, and almost nothing about conventional commercial construction assumes that setting.
A shop front is designed to be welcoming, which means level thresholds, glazed frontage and a floor that continues out to the pavement. Every one of those is a water entry path. There is very little landscaped ground to absorb anything, the site is almost entirely impervious, and there is no room for the surface storage that would buy time on a mainland site. So water that is not taken away by the public system arrives at the door with nothing in between.
The commercial dimension makes the damage disproportionate too. Fit out, stock, equipment, refrigeration and the cost of closing are usually worth far more than the building fabric, which is why an event that would be an inconvenience at a house is an existential problem for a tenant. When nearly every business on the Circle closed for weeks to months after 2024, that was the mechanism.
For association and condominium buildings there is a further dimension: under the structural integrity reserve study requirements, waterproofing and exterior painting is one of the enumerated components a residential condominium association with a building of three habitable stories or higher must include in its study. It is a funded line item rather than a discretionary one. Boards should take the specifics to association counsel.
St. Armands Key and the Sarasota Keys
The useful question here is what your building does in the first ten minutes, because that is the interval the July event actually measured.
St. Armands Circle
The retail, restaurant and gallery core. Almost entirely impervious, served by the pump stations, and the part of the island where an ordinary storm becomes a commercial event fastest. Threshold and entrance detailing does more here than anything else we install.
The Residential Streets
The houses and small buildings on the streets radiating out from the Circle. Slabs at or near grade, vapor barriers from another era, and the same reliance on a pumped system a few hundred feet away.
The Waterfront and Canal Lots
Bayfront and canal front property with seawalls, docks and a fully tidal receiving water. Where drainage and shoreline condition stop being separate subjects and washout from behind a wall becomes the failure mode.
The Neighboring Keys and the Mainland
Conditions differ island by island: Lido Key across the causeway, Longboat Key to the north, Siesta Key and Casey Key to the south. Mainland conditions are on our Sarasota page.
St. Armands Key Drainage and Waterproofing
Why does my yard or my doorway flood after heavy rain or a high tide?
Because St. Armands has a shallow water table, flat sandy ground and no natural low point to drain to. Water leaves this island through a pumped system rather than by gravity, so when the rate of arrival exceeds what the drains and pumps can take, it stays where it landed. That is a capacity condition rather than a defect on your property.
What happened in July 2026?
A faulty sensor kept one of the five stormwater pump stations on the Circle from turning on during a storm, so four were draining into the bay instead of five. A restaurant manager described roughly ten inches of water arriving in about ten minutes. The county fixed the sensor. It is worth knowing about because it shows how little margin the system has when it is not fully operational.
Can you waterproof a slab building on a barrier island?
Yes. Our Seal Tight System was designed for coastal Florida. It is applied to the positive side, the face the groundwater actually touches, and it protects against hydrostatic pressure and salt exposure even when the water table rises to slab level, which is why it works on a building that is already standing.
Will waterproofing help prevent damage from saltwater?
Yes, and this is one of the strongest reasons to do it here. Chlorides reaching reinforcing steel cause it to corrode, and corroding steel occupies more volume than the steel it replaced, so it cracks concrete from the inside and pushes the surface off. Keeping salt bearing water away from below grade concrete interrupts that process. More on our steel corrosion page.
Will this protect my building from storm surge?
No, and we would rather say so directly. Drainage and waterproofing address ordinary weather, groundwater and the slow damage that runs between events. Surge is a different problem, and the City Engineer has made the same distinction about the public resiliency measures, which are aimed at heavy rain events rather than necessarily at surge. Anyone who tells you a drainage system makes a building surge proof is overselling.
Should I wait for the county drainage improvements?
That is your call, and the improvements are real: 13.5 million dollars was approved in December through the Resilient SRQ program, with work expected by the end of 2027. Two things to weigh. That is several wet seasons away, and the improvements target rain rather than necessarily surge. The work on your own property is the part that is available now and the part that does not depend on anybody else.
Why is my slab letting moisture through?
Because water is reaching it and there is nothing between the two. Many buildings here were built with slabs at or near grade with vapor barriers to the standards of their day. Concrete is porous, so once the water table contacts the slab, capillary movement carries moisture upward with no crack involved at all.
How does drainage work reduce the risk of washout under my building?
By controlling where water enters the ground and where it goes afterwards. On sandy coastal fill, concentrated flow carries material with it, which produces voids under paving and slab edges rather than compression of the soil. Stop the concentrated flow and the loss stops. Fill the void without stopping the flow and it returns.
Am I permitted by the City or the County?
St. Armands Key is inside the City of Sarasota, so permitting, inspection and floodplain administration run through the City. The stormwater pump and drain system serving the Circle is managed by Sarasota County. Both are involved in the life of this island and they answer different questions, which is worth remembering when you are trying to find out who to ask.
Do you offer drainage solutions for commercial parking and service areas?
Yes. We repair and retrofit catch basins, storm drains and subgrade failures for commercial, retail and multi family property on St. Armands Key. On this island the subgrade is usually the failure rather than the surface. Details on parking lot drainage systems.
Where can I check my flood risk?
Use the FEMA Flood Map Service Center. For anything that turns on a determination for your specific structure, go to the City of Sarasota directly and get the answer in writing.
Does drainage and waterproofing work carry the lifetime warranty?
Qualifying drainage and waterproofing work carries a lifetime transferable warranty, which means it passes to the next owner of the property. The scopes and the exclusions are set out on our warranties page.
Drainage and Waterproofing Services
- Seal Tight Waterproofing System on the positive side of below grade concrete
- Threshold and entrance detailing for ground floor commercial units
- Geotextile lined perimeter drainage designed for sandy coastal fill
- Designed sump and pumped discharge where gravity is not available
- Subgrade stabilization and void filling under slabs, paving and walkways
- Catch basin, trench drain and storm pipe repair and replacement
- Parking lot drainage systems for commercial and association property
- Grading corrections and gutter and leader discharge
- Vapor retarder detailing under new slabs
- Seawall repair, elevation and replacement, and seawall permitting
- Sheet piling where a bayside edge has to be cut off
When the Water Has Already Done Damage
On sandy coastal fill the structural side follows the drainage side, because the failure mode is material leaving rather than material compressing. The drainage work stops the water. The structural work corrects what has already moved.
- House leveling on St. Armands Key
- Foundation repair in Sarasota
- Commercial foundation repair
- Foundation settlement repair, which explains uniform settlement, tilt, sagging and hogging
- Helical piers, push piers and pipe pile underpinning through loose coastal fill
- Weathered cracks and steel corrosion in coastal concrete
- Flood asset protection and foundation inspection
Statewide context sits on foundation repair in Florida and drainage and waterproofing in Florida.
Where Else We Work
Drainage and Waterproofing Florida · All Locations · Lido Key · Sarasota · Siesta Key · Longboat Key · Casey Key · Venice · Bradenton · Anna Maria Island · Holmes Beach · Port Charlotte · Punta Gorda · Cape Coral · Madeira Beach · Redington Beach · Tampa · Flood Asset Protection · Efflorescence · Steel Corrosion · Warranties
Get a Drainage and Waterproofing Inspection on St. Armands Key
Because Florida has no statewide waterproofing code, you need people who understand local soils, tidal pressure, salt exposure and how the public system on this particular island actually behaves. What the code does require is narrower than most owners think. The Florida Building Code requires grading that falls six inches within the first ten feet of the foundation, and two percent on impervious surfaces within that distance. It requires a real foundation drain only where a foundation both retains earth and encloses habitable or usable space below grade, which a Florida slab on grade building never does. Outside a mapped flood hazard area there is no minimum finished floor elevation above adjacent grade and no elevation certification.
Put plainly, on a typical St. Armands building the detail that would keep water out of the slab is not required and is therefore usually not there. We build it anyway, because the absence of a requirement is not the same as the absence of a problem, and because on this island the public system has already shown what happens when it is running at four fifths.
Under new slabs we detail vapor retarders to ASTM E1745, which caps water vapor permeance at 0.1 perms across all classes and requires 45 pounds per inch tensile and 2,200 grams puncture resistance for Class A. The 2021 IRC raised the residential requirement to a minimum 10 mil Class A sheet with 6 inch lapped joints.
Inspections are free. On St. Armands the first thing we want to establish is what your building does in the first ten minutes of a storm, and what is protecting the concrete for the rest of the year.
Fix the Part You Control
Call for direct help with water reaching a doorway, moisture through a slab, hydrostatic pressure, spalling concrete, washout under paving, or recovery work after an event. We will tell you what is wrong before we tell you what it costs, and we will tell you what we cannot fix.