For terraced retaining walls, a common rule of thumb is to space the upper wall at least as far back as the height of the lower wall, and some references recommend twice the lower wall height for added safety and stability.

Quick rule

  • Basic guideline: at least 1x the lower wall height back.
  • More conservative guideline: at least 2x the lower wall height back.

Example

If the lower wall is 5 ft tall, then:

  • Minimum spacing: about 5 ft.
  • Conservative spacing: about 10 ft.

Important notes

  • Local building codes can be stricter, and some places treat walls that are too close as one combined wall for height and permit purposes.
  • Soil type, drainage, slope, and load near the top wall can change the needed spacing.

If you want, I can help you figure out the spacing for your exact wall heights and slope.