Retaining walls and slope work
Four walls we build, and what every one includes
Each wall below starts with the same buried work. The face is the part you see; the rest decides how it ages.
Drain rock and pipe
Perforated pipe in clean rock behind the wall, wrapped in fabric, with an outlet that runs somewhere sensible.
A compacted base
Crushed rock under the first course, compacted in layers to the depth the design calls for.
Backfill in layers
Soil returned and compacted a layer at a time, so the wall is not left to push against a loose pile.
Haul-off
Soil and spoil leave with us. Where it can stay on site as backfill or grade, the estimate says so.
Permit and engineer work
We look up the rules, prepare the permit package and bring in the engineer when the wall needs one.
Cleanup
Rock, fabric scraps and tracked soil off the driveway and street before we leave.
Wall type A
Segmental block
Interlocking concrete block, stacked with a setback so each course leans into the slope.
A block wall is the neat option: straight lines, even faces and a finished top that takes a planted bed or a path. It suits yards where the wall is seen every day.
At a glance
Best for: clean lines, planted beds and driveway edges
Height: holds itself up to about 3 or 4 feet; taller walls add reinforcing grid laid back into the slope, to an engineer's design
Drains: through the rock behind the wall
Watch for: a wall taller than its base was built for
Wall type B
Rockery
Large boulders fitted in a staggered pattern, each tilted back into the bank.
Rockeries are the Puget Sound classic. They look natural, take plants in the gaps and forgive uneven ground. Boulders come by truck and are placed by machine, so access decides whether one fits.
At a glance
Best for: natural looks, planted banks, front-yard slopes
Height: usually kept to about 4 feet unless an engineer designs it
Drains: through the gaps, with rock and pipe behind
Watch for: a machine path from the street to the wall
Wall type C
Dry-stacked stone
Stone fitted by hand with no mortar, so water passes through the joints.
Dry-stack is slow work and the most personal of the four. Each stone is chosen and turned by hand. It suits low walls, terraces and the edges of steps.
At a glance
Best for: low walls, terraces, garden steps
Height: low; taller dry-stack goes to the engineer
Drains: through every joint
Watch for: cost, because it is done by hand
Wall type D
Gabion
Welded wire baskets filled with hand-placed stone.
Gabion walls flex, drain freely and cope with wet ground. They suit steep banks and the edges of ditches more than a front-yard garden bed, and they look like what they are.
At a glance
Best for: wet banks, steep ground, ditch edges
Height: built in stepped tiers; tall ones go to the engineer
Drains: freely, through the stone
Watch for: stone sized to the mesh, so it does not slump
What we will not do
Three things we don't build, and why
Timber walls
In ground that stays wet most of the year, timber is usually the shortest-lived choice. We point people to block, stone or gabion.
Tall walls from a sketch
If a wall needs an engineer, it is built from the engineer's stamped drawing. We don't start from a napkin.
Poured concrete walls
Formwork and rebar are a specialty. If a design calls for concrete, we bring in a concrete contractor and coordinate the job.
Walls and permits
Questions about the wall itself
Do I need a permit or an engineer?
Often for tall walls, and sometimes for short ones. A common line is about 4 feet from the bottom of the footing to the top, or any wall that holds up a driveway, a building or another wall. Cities set their own rules and mapped steep slopes carry more, so we check yours before we price.
Do you build timber walls?
No. In ground that stays wet most of the year, timber is usually the shortest-lived choice. We build block, rockery, dry-stack stone and gabion walls, and will tell you which fits the slope.
The wall is on the property line. What happens?
We ask for a survey or the corner pins before we set the wall line. A wall that holds a shared bank is a conversation with the neighbor first, and we can join it.
What about the trees on the slope?
Roots hold a bank together, so we work around healthy trees where the design allows. If a tree has to go, a city rule may apply, and we check it when we check the permit.
Walk the slope with us
Tell us where the bank is and what it is doing. We call to set a time to look at it.