Why mountain lots need walls
Most properties in Summit, Grand, Eagle, and Clear Creek County have grade. Driveways climb, backyards drop off, and slopes between the house and the road need terracing to become usable space. Retaining walls turn unusable hillsides into terraced patios, level lawns, planting beds, and play areas.
There are three wall systems we use almost exclusively in the Colorado high country: boulder walls, segmental block walls, and natural stone walls (dry-stack or mortared). Each has its place.
Boulder walls
Massive Colorado moss-rock boulders, dry-stacked with structural soil between courses. Best for naturalized terraces, organic-looking transitions, and walls under about 6 feet tall.
Pros: most natural mountain aesthetic, no manufactured look, durable indefinitely if properly drained, no maintenance.
Cons: requires heavy equipment access to set boulders, irregular face limits how flat you can build it, takes more linear footprint than block at the same height.
Segmental block walls (engineered)
Manufactured concrete units (Allan Block, Versa-Lok, Keystone) designed for engineered retaining walls. Best for clean geometric lines, taller walls (6'+), and long runs where boulder walls would be expensive.
Pros: clean precise face, engineered for tall heights with geogrid soil reinforcement, lower per-foot cost on long runs, predictable construction time.
Cons: less rustic look (though textured face options are good), still reads as 'manufactured' on rustic mountain properties.
Natural stone walls (dry-stack and mortared)
Hand-laid Colorado fieldstone, ledgerock, or quarried stone. Best for accent walls, planter walls, and craftsman-style projects where the wall itself is a design feature.
Pros: most custom and craftsman look, unique on every project, blends perfectly with natural stone hardscape.
Cons: highest cost per linear foot, most skilled labor required, slowest construction.
Engineering and permits
Most Colorado mountain jurisdictions require a permit and engineered drawings for any retaining wall over 4 feet tall — measured from the bottom of the footing to the top of the wall. The exact threshold varies by jurisdiction (Summit County, Grand County, Town of Vail, etc.).
Engineered walls require geogrid soil reinforcement (woven mesh layers tied back into the slope), specific backfill specifications, and stamped drawings. The engineering cost is typically a small fraction of the wall cost, and it's not optional — un-engineered tall walls fail and the rebuild cost is enormous.
Drainage: the #1 cause of wall failure
Almost every retaining wall failure we see in Colorado traces back to one cause: water built up behind the wall, froze, expanded, and pushed the wall out of plumb. Once a wall starts to tip, it doesn't recover — it has to be rebuilt.
Every properly built wall includes: perforated drain tile at the base, free-draining gravel backfill (3/4" angular drainage rock, not native soil), geotextile fabric between the drainage zone and the soil behind it (prevents fines from clogging the drain), and weep holes or daylight outlets to actually move water away from the wall.
If a contractor proposes to backfill your retaining wall with native soil and no drain tile, walk away.
