Retaining Walls

Half the lots in this part of the Bay Area are on a slope. A retaining wall is what turns the useless part of that slope into flat, usable yard — and it is also the piece of construction on a residential property where failure is least forgiving, because a wall that goes does not go quietly.

Ten years of building them here means the most useful thing we can tell you comes before any of the design: what actually makes them fail.

Drainage is the whole job

A retaining wall does not usually fail because the wall was too weak. It fails because the wall became a dam.

Saturated soil is dramatically heavier than dry soil, and water trapped behind a wall exerts hydrostatic pressure that no reasonable wall thickness is designed to resist. Bay Area clay makes it worse: it swells as it takes on winter water, pushing outward on top of everything else.

So a wall that lasts has a drainage system built into it, and most of the cost you cannot see is here:

• Gravel backfill behind the wall, so water moves down instead of pooling against the face
• A perforated drain pipe at the base, sloped to somewhere water can actually go
• Filter fabric between the soil and the gravel, so fine material does not migrate in and silt the drainage up over a few winters
• Weep holes through the face where the wall type calls for them

A wall with no drainage will look identical to a good one on the day it is finished. You find out the difference in the third or fourth wet winter.

Height changes what kind of project this is

Short garden walls — knee height, holding a planting bed — are straightforward landscape construction.

Once a wall gets taller, it stops being landscaping and becomes structure. The soil load grows faster than the height does, and jurisdictions here typically require a permit and an engineer’s drawing above a threshold that varies by city and by whether there is a surcharge above the wall — a driveway, a structure, or another slope.

That is a conversation to have at the start, not after the design is settled. We will tell you plainly when what you are describing is in that territory, and what it means for the timeline, rather than quietly building something shorter than what the site needs.

What we build

• Concrete block walls, reinforced and filled — the workhorse for most residential situations
• Poured concrete walls where the situation calls for it
• Segmental block where the look matters as much as the function
• Terracing — two or more shorter walls stepped up a slope, which is often better engineering and better-looking than one tall wall
• Repairs — replacing failed sections, adding drainage to a wall that never had any, and rebuilding walls that have started to lean

The warning signs worth calling about

An existing wall rarely fails without notice. Call if you see any of these:

• The wall leaning outward, or bulging in the middle
• New cracks, especially stepped cracks that follow the block joints
• Soil or gravel escaping from behind it
• Water seeping through the face, or standing water behind it after rain
• The ground above it separating or slumping

Caught early these are usually a drainage retrofit and a section repair. Caught late they are the whole wall.

What it looks like while we are there

Excavation is the disruptive part — heavy, dirty, and dependent on access to get equipment and material into the yard. Narrow side gates and steep approaches change the method, so we look at access on the first visit.

Block work goes up in courses, with grout and curing time built into the schedule. The yard around the work is not usable while it is happening.

Across the Bay Area

We build retaining walls in San Rafael, Tiburon, Mill Valley and across Marin, in San Francisco, and out through Berkeley, Orinda, Walnut Creek and Vallejo.

Every property gets walked in person before we settle on a wall — the slope, the soil, what is above and below, and where the water currently goes. Call and describe the slope, and mention roughly how much height you are trying to hold back.