Site Work, Excavation, and Foundations
Site Work, Excavation, and Foundations covers what happens before and below the slab: layout, clearing, grading, excavation safety, stormwater controls, soil bearing, and footing design. Florida conditions - high water table, sandy soils, and flat terrain - shape nearly every answer.
Excavation and trench safety
- Call Sunshine 811 at least two full business days before excavating; the day of the call does not count.
- Under OSHA 1926 Subpart P and Florida's Trench Safety Act, trenches 5 feet deep or more require a protective system; at 20 feet or more, a registered professional engineer must design it.
- Maximum slopes: Type A soil 3/4:1, Type B 1:1, Type C 1.5:1. Sandy Florida soils rarely qualify better than Type C, and standing water forces a protective system regardless of soil type.
- Spoil and equipment stay at least 2 feet back from the edge; a ladder or ramp within 25 feet of every worker in a trench 4 feet or deeper; a competent person inspects daily and after rain.
Stormwater and erosion control
- Disturbance of one acre or more requires coverage under the FDEP construction generic permit: Notice of Intent, a Stormwater Pollution Prevention Plan, inspection records, and best management practices such as silt fence, inlet protection, and a stabilized construction entrance.
- Keep the SWPPP on site and update it when the sequence changes.
Foundations
- Footing area equals load divided by allowable bearing pressure, taken from the geotechnical report - never assumed.
- Confirm bearing on undisturbed soil, provide minimum footing width and thickness, reinforcement per plans, termite treatment, and dampproofing.
- In flood zones, the elevation of the lowest floor and the foundation type (pile, stem wall, slab) must match the design.
Worked example
A column delivers 60 kips dead plus live to a spread footing. The geotechnical report allows 2,000 psf. Required area = 60,000 lb / 2,000 psf = 30 square feet, so a 5.5-foot square footing. Check self-weight: a 5.5 x 5.5 x 1.5 foot footing weighs about 6.8 kips, roughly 250 psf at the base. Add it: (60,000 + 6,800) / 2,000 = 33.4 square feet, so use a 5.8-foot square, rounded to 6 feet. Ignoring footing weight underprices the concrete and undersizes the bearing area.
Traps that cost marks
- Counting the call day toward the 811 two-business-day notice.
- Sloping a trench in saturated or previously disturbed soil.
- Assuming a 4-foot trench never needs protection when the spoil pile is at the edge.
- Treating imported fill as bearing soil without compaction testing.
- Forgetting the SWPPP inspection log, which is a permit violation even when the site looks clean.