New Hillside Residence, Mill Valley

This undeveloped lot in the hills of Mill Valley is steep and downsloping with a view of Mt. Tam. We wanted to re-create an architecture that resonates with the landscape as well as refers back to the wood domestic architecture of early Mill Valley. The project is designed to relate to the existing land forms. The building steps down the hill to a flat bench area.  Along the side elevations the massing is broken down into distinct cedar “cabin” elements which sit on top of a darker wood “ground” plane, such that the bottom level of the house appears to be a wooden rock. Proposed materials include a natural wood exterior, dark metal sloping roofs and flat “green” roofs, and dark metal windows. Carefully placed landscape elements complement the residence and reinforce the “rock” as well as shield it from adjoining neighbors

This unimproved parcel unofficially referred to as New Hillside Residence (APN 027-131-34) is a down-sloping lot on the west side of Tamalpais Avenue with an effective lot area of 22,223 square feet; it is zoned RS-20. The site is located where the upper end of Tamalpais meets Summit Avenue and, therefore, has easier vehicular access than many of the other Tamalpais Avenue addresses.

Our site strategy is driven by the naturally occurring terraced areas on the property, in order to minimize overall construction impacts to the neighborhood. The project also aims to preserve most of the unimproved property in its natural condition (e.g. large rock outcropping and surrounding vegetation). The 31 inch oak tree (a heritage tree) on the upper portion of the lot has been evaluated by an arborist (MacNair and Associates) and deemed a hazard due to its poor structural integrity (significant decay and large cavity at the base).

The project massing tries to avoid impacts to the neighbors to the north by not extending beyond the uphill edge of the lower structure, and by putting the open car deck on the side property line to give some space between the neighbors’ uphill house and the garage at 315 Tamalpais. The views to Mt.Tam for the neighbor to the south are preserved.

Multiple site strategies were considered in evaluating access to the property. Initially, a larger driveway and auto court were contemplated, similar to the neighboring property at 309 Tamalpais. This proved infeasible because of maneuverability challenges, substantial grading connected to the driveway, and a heavy concentration of impervious surface. Instead, we pursued a site strategy that places parking at the top of the lot directly adjacent to Tamalpais Avenue; this is similar to several property development patterns along Tamalpais Avenue, especially for down-sloping lots. The project includes two parking spaces within the garage, and one additional guest parking space in the driveway area parallel to the outside of the garage. The second unit’s dedicated independently accessible space is located adjacent to the garage.

There is limited street parking along the lot frontage. As a result, we are exploring improvement to the Tamalpais Avenue right-of-way to create at least 2 new parallel parking spaces on the eastern edge of the roadway where, based on the existing erosion pattern, trucks routinely park. This would involve construction of a small retaining wall along the eastern edge of Tamalpais. The Planning and Building Department and the Fire Department confirm feasibility and support for these public improvements. Not only would these spaces benefit the neighborhood, but they also would facilitate early construction staging.

The new house is centered on the uniquely shaped lot to maintain existing vegetation around the periphery. Indoor spaces and outdoor decks are positioned to gain views of Mt. Tam. The garage is setback 7 feet from the front property line as allowed under 20.60.080 of the Municipal Code. Only the garage can be seen from the street.  

The proposed adjusted floor area of the project is 4,072 square feet, which excludes the exempted 500 square foot attached garage and 500 square foot attached second unit.

The residence will “read” like many other homes on the down-slope of Tamalpais when viewed from the street – a single story garage rising approximately 8 feet above the edge of payment. The second unit and primary residence will be located entirely below the Tamalpais roadway to reduce the visual appearance from the public realm and to take advantage of a flat entry courtyard.

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