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Marin Hillside Drainage & Waterproofing (415) 555-0100

Serving Mill Valley, San Rafael, Ross Valley, Novato & Southern Marin

Retaining Wall Drainage for Marin Hillside Properties

Most retaining walls fail because of water, not weight. If your wall is leaning, cracking, weeping, or bowing after storms, the drainage behind it is usually the problem we look at first.

  • Back drains with perforated pipe, drain rock, and filter fabric
  • Weep hole clearing and new relief outlets in existing walls
  • Drainage for wood, concrete, block, and boulder walls
  • Locally Focused in Marin County
  • CSLB-Licensed Contractors Only
  • Free to Request, No Obligation

Request a Marin Drainage Estimate

Free to request, no obligation. We'll call you back to talk it through.

Prefer to talk? Call (415) 555-0100

Why water is the enemy of retaining walls

A wall designed to hold back soil is often not designed to hold back saturated soil. When water cannot escape, hydrostatic pressure can far exceed the soil load the wall was built for. On Marin hillsides with expansive clay, the seasonal swelling adds another push every winter.

Warning signs

The top of the wall leaning outward. Horizontal cracks or bulges in the face. Wet stains, efflorescence, or water flowing out of joints. Weep holes that never drain or are buried. Wood lagging that is rotting or bowing between posts. Soil settlement or cracking in the area behind the wall.

Drainage options for existing and new walls

For new or rebuilt walls, a proper back drain includes a perforated pipe at the base, a zone of clean drain rock, and filter fabric, with outlets through or around the wall. For existing walls, options include clearing and adding weep holes, installing an interceptor drain uphill, or excavating and adding a back drain section by section.

Walls over a certain height or that support a structure, driveway, or slope typically require engineering and a permit. Severely failing walls may need structural repair or replacement in addition to drainage.

Retaining Wall Drainage near you

Available throughout Marin County, including:

Frequently asked questions

Can drainage fix a leaning retaining wall?

Drainage can stop further movement caused by water pressure, but it cannot pull a wall back into place. If a wall has moved significantly, a structural repair or replacement may be needed along with new drainage.

What are weep holes and why are mine not draining?

Weep holes are openings that let water escape from behind a wall. They often clog with soil or are buried by landscaping. If there is no drain rock behind them, they may never have worked well. A contractor can clear, add, or redesign them.

Do retaining wall projects in Marin need a permit?

Many do, especially walls over about four feet measured from the bottom of the footing, or walls supporting a surcharge such as a driveway or slope. Requirements vary by town, so your contractor will confirm.

Who works on retaining wall drainage?

Licensed specialty contractors and Class A general engineering contractors handle drainage and wall work. For larger walls, a civil or geotechnical engineer may design the system.