Retaining wall maintenance before rainy season: a San Diego checklist

Last Updated: October 27, 2026

Retaining wall maintenance before rainy season comes down to one job: making sure water that reaches the soil behind the wall has a way out, and that less of it gets there in the first place. Clear the weep holes and drain outlets, point downspouts away from the top of the wall, turn irrigation down, and check that the ground above slopes away from the wall. Batterline San Diego Retaining Walls put this checklist together because the timing here is so lopsided. Under NOAA’s 1991-2020 climate normals, November through March supplies 8.10 of the 9.79 inches Lindbergh Field gets in a year, about 83%, and El Cajon and Ramona show the same share. A wall that drains poorly can look fine all summer and then take months’ worth of water in a few storms.

Why the wet season is when walls move

Soil behind a retaining wall pushes on it all year, but saturated soil pushes harder. Water adds its own weight, and when it can’t drain it builds pressure against the back of the wall that the design may never have assumed. That is why most retaining walls are built with a gravel zone and a drain behind them: the gravel lets water fall to the bottom, and the drain carries it away before pressure builds. The City’s standard block wall design in Information Bulletin 221 calls for a 12-inch gravel layer behind the wall and a 4-inch perforated pipe in a filter sock along its full length, discharging to a stormwater collection system, and it prohibits wall drainage that empties onto a neighboring property. County standard walls use 4-inch drains every 6 feet along the bottom course.

San Diego rain also tends to arrive in bursts. On January 22, 2024, Lindbergh Field recorded 2.73 inches in a single day, the highest daily total in the station’s NOAA daily record back to 1939. A drain that is half blocked can keep up with a drizzle and fall behind in a day like that. Clay soils make it worse: they swell as they wet and shrink as they dry, and the guide to expansive clay soil explains how that cycle loads a wall.

What to clear and check before the rains

Do this on a dry day, from the ground, and photograph what you find. Photos from before the season are the easiest way to tell later whether a crack or a lean is new.

Weep holes and open head joints

Weep holes are the small openings near the base of a block or concrete wall; some block walls leave vertical joints open instead. Look for holes packed with soil, mulch, roots or spider webs, and for stains that show where water used to come out and no longer does. Clear what you can reach from the face with a stick or a gentle stream of water. If a hole is dry after every storm while the soil above stays soggy, the blockage is probably deeper than the face. The weep hole guide covers what they do and why some walls have none.

Drain outlets and where the water goes

Find where the wall’s drain pipe comes out: the end of the wall, a cleanout, a pop-up emitter in the lawn or a connection to a curb outlet. Make sure the opening is clear and that the water has somewhere to go once it leaves. An outlet buried under new landscaping, crushed by a mower or pointed at the bottom of the same wall defeats the drain. If you cannot find an outlet at all, the wall may have been built without one; homeowners report inheriting walls that previous owners built with no drain or footing at all.

Downspouts and the top of the wall

A downspout that empties within a few feet of the top of a wall sends a roof’s worth of rain straight into the soil the wall holds back. Extend it or redirect it so the water lands well away from the wall and runs off rather than soaking in. The same goes for patio drains and pool overflow lines that discharge above a wall.

Irrigation above the wall

Sprinklers and drip lines above a wall keep the soil behind it wet all year, and the rains then land on ground that is already near saturation. Turn irrigation on the upper side down or off for the wet season, look for heads that spray the wall or the soil right behind it, and fix leaks. Homeowners report water seeping from below walls when it hasn’t rained; a leaking line above is one common explanation, though a neighbor’s irrigation or groundwater can cause the same symptom.

Surface grading and swales

The ground directly above a wall should slope away from it or into a swale that carries water to the side. Look for low spots where water ponds, planting beds that have been built up against the back of the cap, and paths that channel runoff toward the wall. Yard-wide drainage design is outside what Batterline offers, but the strip of ground that feeds a wall is part of retaining wall drainage work.

The face, the cap and the base

Walk the wall’s length and look for caps that have shifted, blocks that have moved out of line, mortar or stucco cracks, and soil or fine sand on the ground in front of the wall. Sight along the top from one end: a straight wall that now curves outward in the middle is telling you something.

Signs that need more than a cleanout

Some findings mean the wall’s problem isn’t the outlet. A wall that leans outward at the top, a bulge in the middle of its height, stair-step cracks through block, a gap opening between the wall and the soil or paving above, and fine soil washing out through the joints all point to pressure the wall isn’t handling or a drain that has failed below ground. Clearing weep holes on a wall like that treats the symptom.

None of these signs proves a single cause on its own. A lean can come from water, from a footing that was undersized, from a driveway or fence added above the wall after it was built, or from ground that is moving under both. The guide to a leaning retaining wall walks through the causes, and the retaining wall assessment sorts what you’re seeing into a planning level. Where the drainage behind the wall has failed, a lasting fix means opening the drainage zone, which is retaining wall repair rather than maintenance, and where the wall itself is failing along its length, the decision moves toward replacement.

Keep people and pets out from under a wall that is bulging or has moved since your last photos, and don’t dig behind it to look at the drain. Removing soil next to a stressed wall can change how it is loaded.

What a seasonal check can’t tell you

A walk-around shows the outlets and the surface. It can’t show whether the perforated pipe is crushed, whether the gravel behind the wall has filled with silt, or whether the wall was built with a drain at all. It also can’t tell you whether the wall is the right type and size for what it holds back; that depends on its height from the top of the footing, the soil and the load above, which is what a site visit measures. If you are planning new work, the cost estimator gives a budget range, and the cost guide explains why a drainage retrofit behind an existing wall is priced from the site rather than a published range.

If a storm gets there first

If a wall moves, cracks or drops soil during a storm, take photos, keep clear of it, and read the guide to a retaining wall after heavy rain for the order of next steps. Coverage for storm damage depends on your policy, so ask your insurer how it treats walls and earth movement before assuming either way; the storm damage and insurance guide lists what to document. For a look at your wall before the rains, ask for an estimate with the address, a few photos and what sits above it.