Concrete driveways in Fort Lauderdale, built for sand, rain and salt air

What South Florida ground and weather do to a slab

Most of Broward County is built on fine sand laid over porous limestone. Sand is a decent thing to pour on in one respect: it does not swell and shrink with moisture the way clay does, so the heaving that wrecks slabs in other parts of the country is rarely the story here. The trouble with sand is that it moves when water moves through it. Runoff that pours off a roof edge or out of a downspout can carry fine grains out from under the edge of a driveway, a little with every storm, until the slab is bridging a hollow and cracks across the unsupported corner.

The water table is the second factor, and around Fort Lauderdale it sits close to the surface. In the dry months you may dig a couple of feet before hitting damp sand. By late summer, after weeks of afternoon storms, the same hole can fill with water much sooner. Neighborhoods near the Tarpon River, the New River and the finger canals feel it most, and king tides in the fall can push brackish water up through storm drains and onto low streets even on a sunny day. A subgrade that goes soft when it is saturated will let a slab settle unevenly, and a slab poured on wet, poorly compacted fill tends to show it within the first couple of years.

Then there is the rain itself. From roughly late spring through fall, heavy afternoon storms are routine, and an inch or more can fall in a short burst. Water needs somewhere to go. A driveway that pitches toward the garage, a patio that drains back against the house, or a walk that sits a little lower than the lawn beside it will hold water, grow algae and stain, and feed the sand erosion described above. Getting the slope right is one of the least glamorous parts of the job and one of the most important.

Sun and heat work on the surface. Concrete poured on a hot, breezy day loses water from the top faster than it can cure, which leads to fine shrinkage cracks and a weak, dusty surface layer that wears away early. Dark colors and sealed decorative finishes also get hot underfoot and can fade or turn chalky if the sealer is not suited to strong year-round sun.

Near the coast, salt is the slow threat. Salt air and wind-blown spray settle on concrete and work their way in over years. When chlorides reach the steel reinforcement, the steel rusts, rust takes up more room than the metal it came from, and the expanding rust pops pieces of concrete off the surface. That is spalling, and it is common on older slabs, steps and pool decks east of the Intracoastal. Enough cover over the steel, a dense mix, and a good sealer are the defenses.

Finally, trees. Live oaks, ficus and royal palms planted close to a driveway send roots under the slab, and a root that thickens over the years will lift and crack a section of concrete as surely as any settlement will. Hurricanes add their own stress: uprooted trees tear up slabs, storm surge and flooding wash out fill along the edges, and heavy debris trucks and cleanup equipment roll across driveways that were never meant to carry them.

New slab or repair: how to tell which you need

Plenty of tired concrete in Broward does not need to be torn out. Plenty does. The difference usually comes down to whether the problem lives in the surface or in the support below it, and a homeowner can learn a lot by walking the slab slowly with that question in mind.

Signs the slab is a repair or resurfacing candidate

Hairline cracks that have not opened or shifted, a surface that has worn rough or lost its original color, rust stains from sprinklers on well water, mildew and algae in shady spots, and small shallow spalls in otherwise solid concrete are usually surface issues. Crack routing and sealing, patching, pressure cleaning, a polymer-modified resurfacer or a decorative overlay, and a fresh sealer can make a sound slab look and perform far better for years.

Signs the slab needs to come out

Sections that have dropped so one edge sits higher than its neighbor, cracks wide enough to catch a heel or grow grass, broken pieces that rock when you step on them, widespread spalling with exposed rusted steel, and large areas where water ponds every time it rains all point to trouble below the surface. Coating over those conditions hides them for a season at best. Replacing the affected sections, or the whole driveway, lets the contractor correct the base and the slope at the same time.

When the problem is not the flatwork at all

If cracks run from the driveway straight into the house, if doors inside have started to stick, or if the garage floor and the foundation wall are separating, the settlement may be tied to the structure of the home. That is a separate specialty handled by foundation engineers and foundation repair firms, not a flatwork job. Lifting a sunken slab by pumping grout or foam under it is also its own trade. A good flatwork contractor will tell you plainly when what you are seeing belongs to one of those specialists instead.

Request a site visit

Send the address and a few words about the slab: new driveway, cracked patio, worn stamped finish or something else. A reply comes back to set up a visit.

Four kinds of residential concrete work

Residential jobs around Fort Lauderdale tend to fall into four groups, and a single project often touches two or three of them. A new or replacement driveway starts with demolition and hauling of the old slab, then grading, compacting the sand base, placing reinforcement, forming and pouring. Stamped concrete adds color and a pressed pattern that can imitate stone, slate or brick, and is a popular choice for entries and pool areas. Repair and resurfacing covers crack work, patching, spall repair, overlays and sealing on slabs that are still sound underneath. Patios and walkways bring the same rules about slope and base down to the backyard and the side yard, where drainage away from the house matters as much as the finish.

Asphalt driveways are uncommon in this part of Florida, and most homes here have concrete for good reason: it stays cooler, reflects light, stands up to standing water better, and does not soften in a long summer. Interlocking pavers are the other common choice, and they can be a good one, but they bring their own upkeep with weeds, ants and shifting joints in sand. The contractor can talk through the tradeoffs if you are weighing the two.

What a solid concrete proposal spells out

Two quotes for the same driveway can look wildly different, and often that is because they describe two different jobs. Before comparing totals, make sure each proposal answers the same questions. If a line is missing, ask for it in writing.

• The exact area being poured or repaired, with a simple sketch showing where each section starts and stops.
• Slab thickness, and whether it thickens at the edges and where the driveway meets the street apron.
• How the old concrete will be removed and hauled, and how the sand base will be graded, compacted and tested before the pour.
• Reinforcement: wire mesh, rebar or fiber, what keeps it raised to mid-depth instead of resting on the sand, and how much cover it will have.
• The mix strength, whether the supplier will be asked for a mix suited to coastal exposure, and any admixtures for heat.
• Where control joints go and how deep they are cut, since joints decide where the slab will crack.
• The slope and direction of drainage, especially away from the garage, the house and any pool deck.
• Finish, color and pattern for stamped work, and which sealer will be applied and when.
• Curing method, how long before foot traffic, cars and heavy trucks, and what the homeowner should do in the first weeks.
• Who handles the permit and any HOA approval, what is excluded, and what a hidden condition would change.

Permit rules for driveways, aprons and the section of concrete in the public right of way vary from one Broward city to the next, and many neighborhoods also have HOA color and pattern rules. Check with the city or the HOA early, because an approval can take longer than the pour itself.

Scheduling around the rainy season and hurricane season

Concrete can be poured here in every month, which is a real advantage. The planning challenge is not cold weather but water and heat. The drier months, roughly late fall through spring, are the easiest time to pour: the ground is firmer, the afternoons are calmer, and there is less chance of a storm landing on a slab that is still being finished. That also makes those months busy, so booking ahead helps.

Summer pours are common and perfectly workable with some care. Crews often start at first light to place and finish the concrete before the hottest part of the day and before clouds build in the afternoon. They may wet the sand base ahead of time so it does not pull water out of the mix, keep plastic sheeting on hand in case a shower rolls in, and use curing compound or wet curing to keep the surface from drying too fast. If the base is flooded from days of rain, a good contractor will wait rather than pour on mush.

Hurricane season runs from June through November, with the most active weeks usually in late summer and early fall. A project that is torn out and half-finished when a storm approaches leaves loose forms, rebar and debris in the yard. If you are replacing a driveway during those months, ask the contractor how they handle a storm watch, whether forms and materials will be secured or removed, and how the schedule shifts afterward, when every trade in the county is suddenly busy with cleanup work.

Once the concrete is down, plan for the cure. Foot traffic is usually fine within a day or two, passenger cars after about a week, and heavy vehicles such as moving trucks or a loaded pool service truck after a longer wait. Concrete keeps gaining strength for weeks, and sealer on a new slab is typically applied only once it has cured enough. The contractor will give exact numbers for your mix and the weather that week.

Neighborhoods across Broward County

Requests come from all over Fort Lauderdale, from the older streets around the Tarpon River and Rio Vista to the newer subdivisions further west, and from the Broward cities around it. Each area has its own mix of lot sizes, tree cover, distance from the ocean and height above the water table, so the right slab for a canal-front yard in Hollywood is not always the right slab for a long driveway in Davie. The contractor sizes the job to the street and the lot rather than a standard template.

If your street is elsewhere in Broward County, send the address anyway. The contractor covers much of the county and will say quickly whether the property is within reach.

Keeping a new slab in good shape

Concrete here needs less care than most outdoor surfaces, but a few habits add years. Keep downspouts and gutter runoff pointed away from slab edges so the sand below stays put. Rinse off salt residue now and then if you live near the water, and reseal decorative and coastal concrete every few years, or sooner if water stops beading on the surface. Clean up rust from irrigation overspray before it sets, and aim sprinklers away from the driveway when you can. Keep new trees well back from the slab, and have the contractor look at any crack that starts growing wider rather than waiting for it to break into pieces.

Fort Lauderdale concrete questions, answered plainly