Concrete Slabs on Sandy Soil in Central Florida

A concrete slab on Central Florida sand holds up when the sand is clean, compacted in layers and kept dry at the edges. Around St. Cloud the ground is mostly pine flatwoods soils such as Smyrna and Myakka, which the USDA describes as poorly drained, with a water table within 18 inches of the surface for one to four months in most years. This guide explains what that means for a slab and how the base is prepared.

Last reviewed November 2026.

Concrete on sandy soil: the St. Cloud ground

Two flatwoods soils common around St. Cloud (USDA Official Series Descriptions)

Soil	USDA description	Water
Smyrna	Very deep, poorly to very poorly drained, formed in thick deposits of sandy marine materials	Water table under 18 in for 1 to 4 months in most years; 12 to 40 in for more than 6 months
Myakka (Florida's state soil)	Very deep, very poorly or poorly drained, mainly in mesic flatwoods of peninsular Florida	Slow internal drainage; slow to ponded runoff

Sources: USDA NRCS Official Series Descriptions, Smyrna (rev. 11/97) and Myakka (rev. 02/2013).

Sand isn't the enemy of concrete. Clean sand compacts well, drains fast at the surface and doesn't swell like clay. What the flatwoods add is water: a water table that rises toward the surface in the wet season and slow drainage when it does. A slab built for that sits a little higher than the ground around it, on a base that won't wash out.

Slash pine flatwoods at Holopaw State Forest beyond a mowed roadside — Pine flatwoods at Holopaw State Forest.

How the base is prepared

Strip sod, roots and any organic layer; dark, spongy material compresses and rots under a slab.
Bring low areas up with clean fill, placed and compacted in thin layers rather than dumped in one lift.
Compact the native sand the slab will sit on; loose sand settles under the first heavy load or the first soaking.
Set the slab top above the surrounding grade and shape the ground to fall away from it.
Move downspouts, AC condensate lines and sprinkler heads so water doesn't run along the slab edge.

Why edges fail first

Most cracked slabs and sunken driveway panels around here trace to water at an edge: a downspout dumping at a corner, a sprinkler soaking the same strip every morning, or a leak in an irrigation line underneath. Running water carries sand out from under the concrete, and the slab cracks across the void. The repair options are on the driveway repair page.

Lots near the lake

Homes close to East Lake Tohopekaliga and the wetlands around it, along the Narcoossee shore for example, tend to sit on the wettest ground. Fill, compaction and drainage matter most there, and pours are best scheduled in the dry season; the rain and heat guide gives the dates.

Lily pads and marsh grass on East Lake Tohopekaliga.

Concrete on Sandy Soil: Questions

Aerial view of single-story homes and long concrete driveways among trees in Florida

Long driveways and big lots in a wooded Florida neighborhood.

Can you pour concrete on sand?

Yes. Clean sand compacted in layers is a good base for slabs, driveways and pads, and most Central Florida slabs sit on it. The problems come from sand that is loose, full of roots or organic matter, or washed out from under the slab by water running along an edge.

How high is the water table around St. Cloud?

On the common flatwoods soils it rises close to the surface in the wet season. The USDA's description of the Smyrna series, typical of Osceola County flatwoods, puts the water table within 18 inches of the surface for 1 to 4 months in most years and between 12 and 40 inches for more than 6 months. Lots near lakes and wetlands can sit wetter.

Do I need fill under a new slab?

Often, on low lots. Raising the slab area with clean, compacted fill keeps the concrete above where water collects after storms and lets the grade fall away from it. On a lot that is already high and firm, the native sand is compacted and used as is.

What is Myakka sand?

Myakka fine sand is Florida's state soil, a very deep, poorly drained soil of the pine flatwoods. The USDA describes it as having slow internal drainage and slow to ponded runoff, which is why water lingers on flatwoods lots after heavy rain.