Regrading a Flood-Prone Yard with a Slab Foundation: Strategies and Costs

A Florida slab home on a former creek lot has yard sloping toward the house, T1-11 siding at/below grade, sidewalk 6 in below slab, and 75 ft to street. Heavy rains flood the yard and street.

Immediate Priorities

1. Replace T1-11 with fiber-cement (Hardie) siding – $2,000–$2,500 DIY. T1-11 rots fast at grade.
2. Establish 3–4 in clearance between new siding and grade.
3. Minimum 2% slope (18 in drop over 75 ft) from house to sidewalk. Current 4 in drop (0.4%) is essentially flat.

If Sidewalk Blocks Slope

• Install area drain 10–15 ft from house, pipe under sidewalk to curb.
• Or remove/repour sidewalk at lower grade (ramped to neighbors).

Swale Design

Shallow (3–6 ft wide, 1 in deep per ft width), rounded edges, grassed. Not a deep ditch.

Equipment

Skid-steer (Bobcat) with skilled operator for fine grading. Backhoe for trenches only.

French Drain Limitation

At 1% slope, French drains hold water. Need ≥2% for gravity flow.

When to Call an Engineer

If no outlet exists, a civil engineer ($85–125/hr) or county engineer must assess connection to storm system. Raising the slab costs $10k–$20k.

Gutters First

Install gutters with downspouts piped 10+ ft from foundation. This alone may solve splash-back and reduce saturation.