In Orlando, we often see that the real challenge isn't just the sand, but the limestone underneath. The Floridan aquifer system creates a karst landscape where shallow cavities can surprise even experienced drillers. A proper shallow foundation design here must reconcile the loose surface sands—common in the Eastern Valley—with the pinnacled rock below. We've worked on sites near Lake Eola where the depth to limestone varied by 15 feet within a single building footprint. That kind of variability demands more than a textbook bearing capacity equation; it requires local geotechnical judgment. Before setting footing elevations, it's wise to combine the CPT test for continuous soil profiling with a seismic refraction survey to map the rockhead topography and detect potential voids beneath the planned pad.
Differential settlement on a karst surface can crack a slab before the drywall goes up. We design footings that bridge the unknowns.
Top questions
How much does a shallow foundation design cost in Orlando?
For a typical residential or light commercial project, the engineering design and report for shallow foundations ranges from US$1,640 to US$2,760. The final cost depends on the number of borings required, the complexity of the karst investigation, and the size of the structure.
What is the typical bearing capacity of sandy soils in Orlando for spread footings?
In the medium-dense sands common to the Orlando area, we typically assign allowable bearing capacities between 2,000 and 3,000 psf. However, this is always confirmed by SPT blow counts and checked against a 1-inch maximum total settlement criterion using Schmertmann's method.
Do I need a geophysical survey for a shallow foundation in Florida?
If your site is in a known sinkhole-prone area or if SPT borings indicate erratic rock depths, a geophysical survey such as ground-penetrating radar or seismic refraction is strongly recommended. It helps detect cavities that a conventional boring might miss between drill points.
What Florida Building Code sections govern shallow footings?
Chapter 18 of the Florida Building Code (based on IBC 2021) governs soils and foundations. It references ASCE 7 for load combinations and requires a geotechnical investigation for all structures, with special inspection provisions for foundations in karst regions.
Can you design a shallow foundation if the soil has high organic content near Orlando's lakes?
Organic silts and peats are common near the lake chains. In these cases, shallow foundations are often not feasible unless the organic layer is thin and can be over-excavated. We evaluate the thickness and recommend either removal and replacement with compacted fill or a transition to a deep foundation system.
