№ 05 · The Services

Retaining Walls

Freestanding and terraced, built for Midwest freeze-thaw.

What it is

A retaining wall holds back soil. That sentence covers everything important: what’s behind it (saturated, freezing, frost-heaving soil) is what fails the wall, not what’s in front of it. Build the wall with that in mind and it lasts. Build it as a stack of pretty stones and it leans in three winters.

When you need it

  • A grade change of more than two feet, especially in lake-country lots that slope to water
  • A terraced garden, planting bed, or stepped walkway
  • A driveway cut or walkout basement that needs the slope held
  • An existing wall that’s bowing, leaning, or pushing forward

How we do it

We dig to the frost line — in this part of Wisconsin that’s forty-two inches minimum, sometimes more on heavy clay. We pour or place a compacted base of three-quarter washed stone, level, and start the wall. Behind every course we backfill with clean drainage stone wrapped in filter fabric, with a perforated drain pipe at the base that daylights to grade. The wall itself batters back — leans into the hill — at about an inch per foot of height. Above four feet we engineer in geogrid reinforcement tied to the soil mass behind. We cap with a flat stone or block that sheds water away from the joint.

Materials and methods

  • Wisconsin lannon and Bedford limestone for natural-stone walls
  • Granite fieldstone for rustic, weathered installs
  • Versa-Lok, Allan Block, Unilock segmental retaining wall systems for engineered work
  • Three-quarter washed stone drainage backfill, never sand or native soil
  • Filter fabric between drainage stone and native soil
  • Frost-line footings — never floating bases on Midwest soil
  • Geogrid reinforcement above four feet of exposed height

A retaining wall is a drainage project that happens to look like a stone wall. Treat it the other way around and water will tell you why that’s wrong.

Related work

See also.