24H Mold Inspection of Encino

Domingo Amestoy, a Basque sheep rancher, bought the old rancho land in 1889, and the tract carrying his name was subdivided out of it decades later into the half-acre and larger lots that still define it. Flat ground, no sidewalks, mature oaks and ficus, and ranch houses from the 1940s and 1950s sitting low to grade. Lot size is what drives the moisture here. These parcels run large irrigation systems on long timers, and seventy years of raised planting beds, added hardscape, and pool decks have buried the original weep screed and foundation vents. Water applied daily against a slab edge or a crawl space vent does not behave like rain, because it never stops for a dry season.

South of the boulevard the ground climbs into the range that walls the valley, and the north-facing slopes here are cut into Miocene marine shale and siltstone rather than the granite of the ranges across the valley. That rock weathers to clay. Clay swells when it takes on water, holds it against foundations for weeks, and moves, which is why so many of these hillside lots carry retaining walls, caissons, and terrace drains. Every one of those systems depends on a subdrain nobody can see, and decades of leaf litter and clay silt plug them quietly. When a line stops draining, water tracks laterally through fill and reaches the uphill wall of a lower-level room.

The reservoir in the hills above, completed by the city's water department in the 1920s, is a closed drinking-water watershed with no public access, and the homes built along the ridge streets that ring it sit on graded pads cut and filled in the 1960s and after. Ridge-top building means the whole lot sheds water toward somebody, and it means flat and low-slope roof designs that were fashionable when these streets were laid out. A flat roof over habitable space has no attic to buffer a leak and no slope to move water off a failing seam, so the first evidence usually appears on a ceiling that has been wet for months.

The coast live oak that gave this place its name stood at Louise Avenue and the boulevard for something close to a thousand years and came down on February 7, 1998, after weeks of El Niño rain saturated its root zone past the point the soil could hold it. That is the corridor's lesson in miniature. What lines the boulevard now is two- and three-story mixed-use and 1960s apartment buildings over tuck-under parking, a construction type the city's 2015 ordinance required owners to retrofit. Those retrofits opened ground-floor walls that had not been opened since they were built, which is often the first time anyone saw what decades of irrigation had done behind them.

Vicente de la Osa built his adobe here in 1849 and the Garnier brothers added a two-story limestone building in 1872, and the reason both stand on this spot is the natural springs that still feed the pond at the state park off Moorpark Street. Springs are evidence of a water table close to the surface, and that has not changed for the houses built around them. North of here the ground drops toward the flood control basin, where a dam completed in 1941 is designed to hold storm water on purpose. Adobe is unfired earth and limestone is porous; both wick ground moisture upward, and sealing the face of a damp wall traps it inside.