Miami is flat, low and wet for half the year. The limestone under it drains well, but the water table is close to the surface, and big trees root just under the grass. Most concrete problems here trace back to one of those facts.
Do I need to worry about drainage with a new slab?
Yes. Drainage is the first thing to settle on any Miami lot. A slab sheds all the rain that used to soak into the ground it covers, and a summer storm can drop a great deal of water in an hour. Every slab needs a fall, usually about an eighth to a quarter inch per foot, and a place for the water to go: a lawn, a swale, a drain. On a flat lot that slope has to be built in on purpose.
My patio or driveway slopes toward the house. What can be done?
Water running toward the house needs to be corrected, because it ends up at the wall and door sills. The choices, from least to most work, are a channel drain cut in along the wall, lifting the low side of the slab if it has settled, or removing the section and pouring it with the right fall. A drain needs somewhere to empty. We check where that can be before recommending one.
Can tree roots crack or lift concrete?
Yes. Tree roots are one of the top causes of broken concrete in Miami. The rock is shallow, so roots of ficus, banyan, live oak, mahogany and royal poinciana spread wide just under the surface. As a root thickens it lifts whatever is above it. Ficus is the worst offender near driveways and walks.
Can I fix the concrete and keep the tree?
Often you can keep the tree. The ways to do it are to move the path away from the trunk, to bridge the root with a thicker reinforced section, to use smaller panels with more joints near the tree, or to switch to pavers there so the surface can be lifted and reset. Cutting large roots near the trunk risks killing the tree or leaving it unstable in a hurricane. Cities here, including Miami, require a permit for tree work, so talk to an arborist and the city first.
My neighbor's new concrete sends runoff onto my property. What can I do?
Start by showing your neighbor what happens in a storm, with a video if you can. Many owners do not realize where their runoff goes. A small curb, a drain or a regraded edge on their side often solves it. If that fails, your city's code enforcement or building office can check whether the paving was permitted and drains as required. Ongoing damage is a matter for an attorney. Our own slabs are sloped to keep water on the owner's lot or send it to the street.
Does clay or soft soil change the job in Miami?
Heavy clay is not the usual problem in Miami, but soft soil is. Three kinds of ground come up. Limestone near the surface is an excellent base once graded. Sand and rock fill are fine when compacted. Muck, the black organic soil found in former wetlands in the west and south of the county, and marl in the far south, are poor bases. They hold water and compress. Where we find them, they are dug out and replaced with compacted rock before any slab goes down.
My gravel driveway turns to mud and washes out. Is concrete the answer?
Concrete solves it for good, and it is the costliest of the choices. A gravel driveway fails here when rain carries the fine material away and the stone sinks into wet ground. A cheaper step is to regrade it, add a proper compacted limestone base and give the water a path off the drive. If you choose concrete, check the lot coverage limit first, because a gravel drive may be counted differently from a paved one.
My patio was poured over an old trench and it settled. Why?
A trench that was filled without compacting keeps settling for years, and a slab poured across it loses support along that line. It happens after sewer repairs, new water lines, pool plumbing and septic removal. The slab cracks on both sides of the trench and dips in between. If the panel is intact, it can be lifted with injected fill. If it has broken, that strip is removed, the trench is compacted in layers and the strip is poured again.
I am in a flood-prone area. Can I build a raised patio or slab?
Maybe, and this one must go to the building department before any design. Large parts of Miami-Dade are in mapped flood zones. Bringing in fill or raising a slab can change how water moves across your lot and onto others, and flood rules may limit it. A patio at ground level drains more simply. Whatever is built, use a dense mix and good cover over the steel, because flood water near the coast is salty.
Why does water stand in my yard for days after a storm?
Because the ground is already full. In the wet season the water table in low parts of the county rises close to the surface, and there is nowhere for rain to go until it drops. Paving more of the yard makes that worse. Keep some open ground, direct roof water away from slabs and do not block the swale at the street, which is there to hold and soak up water.
For a price on your own property, ask for a free on-site estimate with a written quote. Call (786) 705-4727, or text a photo of the concrete to the same number.