Limestone Retaining Wall on Pure Sand: Footing, Frost & Engineering Reality

You're building a 3-ft dry-laid limestone wall on an old sand pit (40+ ft of pure sand). Soil cap: 3–4" clay + 12" topsoil. Questions: subgrade needed? Frost depth? 2-ft deep block sufficient?

Footing: Non-Negotiable

• 10–12" thick crushed aggregate (crusher run), 10–12" wider than wall each side.
• Compacted to 95% Proctor.
• Bottom of first course below frost line (look up your local depth—likely 36–48" in sand country).

Sand Is Tricky

Some sands compact well; others (uniform, rounded) never lock up. A geotech report is worth $500–1,500 if you're building multiple walls. At minimum, call a local wall builder—ask "what footing do you use here?" They know the sand.

2-Ft Deep Block?

Depth (front-to-back) helps stability, but without geogrid or deadmen, a 3-ft gravity wall on sand is marginal. Consider:

• Geogrid every 2nd course, extending 6–8 ft back.
• Or: hire an engineer. Successive 3-ft walls = tiered system = compounded load.

This isn't a "guess and check" site. One failure undermines the whole slope.