Question 1

How high can a DIY retaining wall be?

Accepted Answer

Most building codes allow retaining walls up to 4 feet without an engineered design or permit. Walls over 4 feet typically require a structural engineer and building permit. Some areas set the limit at 3 feet. Always check local codes before building.

Question 2

Do retaining walls need drainage?

Accepted Answer

Yes. Water pressure behind a wall is the most common cause of failure. Install 12 inches of drainage gravel behind the wall, a perforated drain pipe at the base, and filter fabric between the gravel and native soil. Weep holes or a drain pipe outlet are also recommended.

Question 3

Should I bury the first course of a retaining wall?

Accepted Answer

Yes, always bury the first course at least partially below grade (4-6 inches). This provides a stable, level foundation and prevents the wall from sliding forward. Compact the base material thoroughly before placing the first course.

Question 4

What base material goes under a retaining wall?

Accepted Answer

Use 4-6 inches of compacted crushed stone (3/4-inch minus or road base) for the foundation. Level it carefully as the first course determines the alignment of the entire wall. Do not use sand as a base material as it can shift and settle.

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