Questions to ask a retaining wall contractor before you hire

Last Updated: October 27, 2026

The most useful questions to ask a retaining wall contractor are about who is licensed for this wall, who designs it, who pulls the permit, how water will leave it and what sits above it. The answers show whether a bid is for a structure built to hold back soil or for a row of block. Batterline San Diego Retaining Walls offers and manages retaining wall work across San Diego County, and this list is meant for comparing any bid, ours included. It starts with a licensing rule that changed recently and is easy to misread.

What changed in California’s minor-work exemption

Since January 1, 2025, the California Contractors State License Board’s minor-work exemption (Business and Professions Code 7048, as amended by AB 2622) covers jobs under $1,000, up from $500. The higher limit comes with two conditions: the work must need no permit of any kind, and the unlicensed person must not employ any workers. An unlicensed person advertising work up to $1,000 must also say they are not licensed (CSLB Industry Bulletin 24-07).

For retaining walls, the permit condition does most of the work. In the City of San Diego, a wall over 3 feet tall measured from the top of the footing needs a building permit, and so does a wall of any height that supports a driveway, a walkway, a fence, a structure’s footing or backfill steeper than 1.5:1. Unincorporated County lots follow a similar rule. A permitted wall never fits the exemption, whatever the price. The retaining wall permit guide has the full list of triggers.

Questions about license and responsibility

Which CSLB license classification covers this wall?

California licenses the work by trade, so the right answer depends on the wall. The C-29 masonry classification covers block, stone and segmental walls; C-8 covers poured concrete; the A general engineering license covers walls tied to grading, drainage and similar fixed works. A B general building contractor can build a wall within a project that involves at least two unrelated trades, but a wall-only prime contract can run into the limits in B&P 7057(b). The CSLB says a C-27 landscaping contractor can build a perimeter wall only as part of a total landscaping project. Ask for the license number and check it, along with its classifications and status, on the CSLB website.

Who carries workers’ compensation and liability coverage?

Ask who employs the people on site and to see their certificates of insurance. Coverage requirements and what a policy pays for vary, so read the certificate rather than relying on a description of it.

Who pulls the permit?

The permit should name whoever is responsible for the work. If you are asked to pull it yourself, ask why. The City’s owner-builder path uses form DS-3042, Owner-Builder Verification, and is meant for owners acting as their own contractor. Grading and right-of-way work in the City must be done by a California-licensed contractor, apart from an owner grading their own primary residence.

Questions about the design

Does this wall use a standard design, or does it need an engineer?

The City’s Information Bulletin 221 gives standard drawings for grouted, reinforced block walls up to 6 feet on ordinary ground. Walls outside it, including any wall with a surcharge, a fence on top, expansive soil or a mapped geologic hazard, are designed by a California-licensed civil or structural engineer or architect. A good answer names which applies and why. The engineer guide explains the triggers.

What is above the wall, and how is it accounted for?

A driveway, a parking pad, a fence, a pool or a building footing within the wall’s own height of the top changes the design. Ask how the bid treats it. If the answer only mentions the wall’s height, ask again: height alone never decides the design or the permit.

Does the site need a soils report?

In the City, walls over 6 feet, or shorter walls with a surcharge, need a geotechnical report when they sit in certain mapped hazard categories such as landslides, slide-prone formations, liquefaction zones or coastal bluffs. Ask whether anyone has checked the lot’s category, and who will.

Questions about drainage and the ground

How will water get out from behind the wall?

This question separates bids more than any other. Ask what goes behind the wall (gravel, a perforated pipe in a filter sock), how far down it runs, and where the outlet discharges. City standard walls discharge to a stormwater collection system and may not drain onto a neighbor’s property. The retaining wall drainage page and the weep hole guide cover what a sound answer includes.

How will the excavation and reinforced zone be reached?

Footings, the drainage zone and, for segmental walls, geogrid layers all sit behind the wall face. Ask how wide the excavation runs, whether equipment fits or everything is carried by hand, and what happens on the neighbor’s side. An employer whose workers enter an excavation 5 feet or deeper needs a Cal/OSHA permit.

What happens if the ground isn’t what you expect?

Rock, clay, buried debris or an old footing can turn up once digging starts. Ask how the contract handles that, and how a change in scope is priced and approved before work continues.

Questions about repair versus replacement

If the wall exists and is failing, ask what the bidder thinks caused it and what in the scope fixes that cause. Resetting blocks or patching a face on a wall that leans because water or a load above is pushing it leaves the cause in place behind a new face. The repair or replace guide and the leaning wall guide explain how the cause drives the scope, and retaining wall repair and replacement cover each path.

Questions about the estimate and the inspections

Ask what the price covers and what is separate: engineering, a soils report, permit fees, demolition, haul-off, special inspection and restoration of irrigation and planting. The guide to reading a retaining wall estimate goes line by line, and the cost estimator gives a typical range to compare against. Then ask who will be on site for each inspection. City and County standard walls get four (footing, pre-grout, drainage before backfill, and final), and engineered walls add the special inspections their plans call for.

Homeowners report not knowing which trade to call for a wall at all: a landscaper, a general contractor, a mason or an engineer. These questions work for any of them. To have your own wall scoped, ask for an estimate with the address, its dimensions and a photo of what sits above it.