Question 1

How tall can a retaining wall be without an engineer?

Accepted Answer

As a general rule, retaining walls taller than 4 feet (120 cm) should be designed by a licensed structural engineer. Walls under 4 feet used for landscaping can typically be built by DIYers, but you still need a solid base, proper drainage, and soil compaction.

Question 2

How much gravel do I need behind a retaining wall?

Accepted Answer

You should place at least 12 inches (30 cm) of gravel directly behind the wall, from the base up to about 6 inches below the top. The calculator estimates this volume automatically based on your wall dimensions.

Question 3

How deep should the base of a retaining wall be?

Accepted Answer

The base should be excavated below the frost line, typically 6 to 12 inches deep. Lay a 2 to 4 inch layer of compacted gravel or sand as the leveling base. The first course of blocks should be buried at least 4 inches below ground level.

Question 4

How do I calculate how many blocks I need for a retaining wall?

Accepted Answer

Divide the wall area by the visible face area of one block to get the theoretical count, then add 5 to 10 percent for cuts and breakage. This calculator handles the math automatically and supports several standard block sizes.

🧱 Retaining Wall Calculator

📐 Wall Dimensions

🧱 Block Settings

💰 Material Prices (optional)

📊 Results

💵 Cost Estimate

🖼️ Wall Layout Diagram