The hillside neighborhoods above downtown
Sun Valley, the Dominican area, Gerstle Park, and Bret Harte climb the slopes around downtown San Rafael. These are some of the oldest neighborhoods in Marin. Many homes date to the late 1800s and early 1900s, built on raised foundations with crawlspaces or partial basements cut into the hill, long before anyone designed for subsurface drainage.
Sun Valley
Sun Valley's streets run up into the hills north of downtown, with homes on sloping lots that collect runoff from the open space above. The common call is a crawlspace that fills during long storms, with water entering along the uphill stem wall. An interceptor curtain drain on the uphill side, cut down to the clay, usually solves it at the source. Homes tucked against the hillside also get an interior crawlspace drain and sump pump.
Dominican & Gerstle Park
The Dominican area and Gerstle Park are known for large old homes, mature oaks, and stone and concrete garden walls that may be a century old. Those walls were rarely built with drainage behind them. After decades of saturated winters many lean, bulge, or weep at the joints, which calls for retaining wall drainage and, where movement is significant, structural repair. Oak roots are the other recurring issue. Roots find old clay and cast-iron drain lines and fill them, so a camera inspection is a smart first step before replacing anything.
Bret Harte
Bret Harte's hillside streets have steep driveways and homes stepped into the slope. Driveway runoff is a frequent culprit. A sloped driveway can deliver street and uphill water straight to the garage or the lower floor. Trench drains across the driveway and a solid tightline to the curb are standard fixes, alongside subsurface drainage for the uphill side of the house.
Terra Linda: slab-on-grade vs. hillside raised foundations
Terra Linda shows San Rafael's split better than anywhere. On the valley floor are mid-century homes, including some of the Bay Area's best-known Eichler tracts, built slab-on-grade on heavy clay. Up the hillsides along the edges of the valley are homes on raised foundations with crawlspaces. Same neighborhood, opposite problems.
Slab-on-grade homes
A slab has no crawlspace to collect water, so it shows up inside: damp carpet along an exterior wall, water under sliding doors, efflorescence or lifting flooring, and musty rooms after long storms. Terra Linda's clay holds water at the surface, and many slabs sit only a few inches above grade. Many Eichler slabs also have radiant heating tubing embedded in the concrete, so cutting into the slab is a last resort.
- Regrade first. Soil and hardscape should slope away from the slab edge, and planters built up against the wall should be lowered.
- Exterior perimeter French drain. A fabric-wrapped perforated drain along the problem walls, set below the slab edge, intercepts water before it reaches the concrete.
- Tightlines for roof and atrium water. Flat and low-slope Eichler roofs dump concentrated water at a few downspouts. Every leader and the atrium drain should run in solid pipe to an approved outlet.
Hillside raised-foundation homes
Homes on the slopes around Terra Linda behave like the older hillside neighborhoods. Groundwater flows downslope, pools in the crawlspace, and pushes against the uphill stem wall. The answer is the same: intercept uphill, collect underneath, and pump out reliably.
Lucas Valley & Marinwood
Lucas Valley follows Miller Creek west from Highway 101, with mid-century neighborhoods, including more Eichler tracts, on the valley floor and newer homes up the hillsides. The valley floor has deep clay soils that drain slowly, so yards stay soggy and water collects against slab edges. Hillside lots above the valley see seasonal seepage after long storms. Because Lucas Valley and Marinwood are unincorporated, outlets and right-of-way work are permitted through Marin County, and HOA design rules may apply to grading, drains, and visible hardscape.
Discharge in San Rafael
Inside city limits, a curb core or storm drain connection usually needs an encroachment permit from San Rafael's public works department. Collected water should never be sent onto a downhill neighbor, and sump and drain water must never go into the sanitary sewer. On flat Terra Linda and Lucas Valley lots, pop-up emitters can work where there is lawn to absorb the flow. On hillside lots, piped discharge to the street is the safer choice.
Seeing water along your slab or under the house? Call (415) 555-0100 or request an estimate from a San Rafael drainage specialist.
Drainage services in San Rafael & Lucas Valley
- Hillside French & Curtain Drains → Deep interceptor curtain drains, French drains, and downspout tightlines designed for Marin clay and serpentine slopes.
- Crawlspace Waterproofing & Sump Pumps → Interior perimeter drains, cast-iron sump pumps with battery backup, and reinforced vapor barriers for wet Marin crawlspaces.
- Retaining Wall Drainage → Back drains, weep hole relief, and pressure relief for leaning or weeping hillside retaining walls.
Frequently asked questions
My Terra Linda home is on a slab. Can water still get in?
Yes. Slab-on-grade homes get water through the slab edge, under exterior doors and sliders, and up through cracks and the slab itself when the soil under it is saturated. The fix is usually outside the house: regrading, perimeter French drains, and downspout tightlines that keep water from collecting along the slab edge in the first place.
Why does water pool in my Eichler atrium?
Most Eichler atriums drain through a small floor drain that ties into an underground line. Those lines are often original, undersized, and clogged with roots or debris. A camera inspection shows whether the line can be cleared or needs replacing. Many owners add a larger catch basin and a new solid line to the street.
Are older Gerstle Park and Dominican foundations a drainage concern?
Often. Many early-1900s homes have shallow footings, brick or early unreinforced concrete foundations, and basements or crawlspaces dug into the hillside with little or no waterproofing. Keeping water away from those walls with curtain drains, footing drains, and tightlines protects foundations that are hard and expensive to replace.
Who permits drainage outlets in Lucas Valley and Marinwood?
Lucas Valley and Marinwood are unincorporated, so curb cores and right-of-way work go through Marin County. Projects inside San Rafael city limits, including Terra Linda, go through the City of San Rafael. Some neighborhoods also have homeowners association rules for exterior work.