Earthquake-Resistant ADU

Introduction
Located on a steep hillside over a major earthquake fault, the challenge was to build a high-strength ADU on an efficient construction schedule given limited garden access. Adding this unit to the garden was the fastest way to create a separate living space for the property, avoiding lengthy design reviews. The owners are art collectors and voracious readers, and requested computer-modeled daylighting and a deconstructivist motif of discontinuous walls. We proposed a plan with these complex parameters superimposed on the high hazard zone, and devised a system of offset steel frames with a floating roof over surround clerestory windows to capture daylight from the gardens.

The earthquake-resistant ADU also serves as an artistic garden folly, a modern complement to the main house, an historic 1935 William Wurster. As a U.S.-European team, Peek | Ancona began drawing on the landscape, referencing both Land Art and Modernist Mediterranean architecture of the late 20th Century to complement this historic California site. The technical solution was to conceptually let nature take its course through delicately digging into the hillside, compacting the soil above bedrock, then creating a monolithic concrete slab and retaining wall with an ultralight cantilevering composite structure, providing both panoramic mountain views and generous wall space for paintings.

Summary
• The “Earthquake-Resistant ADU” is an innovative house for living in small spaces that remains intact after a major earthquake, requires no artificial light during the day, and, during the summer, is naturally ventilated by the surrounding gardens.
• ADU built area: total enclosed space of 850 sq.ft.., with 1300 sq.ft. of view decks creating borrowed spaces for the interiors. The one bedroom plus bath and kitchen is complemented by ample wall space around the open living/dining rooms to accomodate a unique art collection.
• The house utilizes exclusively sustainable materials, a rain catchment system to irrigate the hillside below, a super-insulating roof, and high-performance LED lighting and radiant floor heating.

Resilience
Earthquake-resistant design: Steel moment frames - Lightweight roof diaphragm - Monolithic concrete foundations - Hillside compaction - Rainwater diversion system

Sustainable Design
Passive solar roof overhangs - Superinsulated roof - Rain catchment system - Summer cross-ventilation -EPA-certified fireplace - No/low VOC finishes - 95% LED lighting - Computer-modeled daylighting - Radiant floor heating - Tankless water heater - ENERGY STAR fixtures

Design | Sustainability |Resilience
• The new house roots itself on the upper hillside, floating cloud-like over the garden, facing mountain views. An efficient, horizontal excavation into the hill top removes as much earth that is filled on the down slope. An eight foot tall retaining wall is located uphill side, integrally poured with the house slab, stabilizing the landscape and providing earth sheltering from the strong California light.

• Mountain view windows are combined with generous roof overhangs for passive solar design. By using a computer model for natural daylighting, the house functions without any operable shades.

• Water conservation is achieved through the highest efficiency fixtures, combined with a roof catchment system for gray water. A low slope roof directs water to a set of drains with integrated overflow devices, reducing debris and pooling.

• Twelve-foot tall steel columns are monolithically poured with an innovative concrete slab, achieved by hollowing out unnecessary areas and pouring the concrete above the subterranean column bases. The column sets are bridged by moment frames to resist earthquakes, minimizing steel in the roof for cost efficiency, while most of the roof is a wood diaphragm for lightness and cost-efficiency.

• While the exterior is a cost-efficient neutral grey stucco to accentuate the abstract building shell and luminous windows, the interiors are painted a pure white to showcase the owner's art collection. The structural columns are weathered steel, echoing the soaring evergreens that punctuate the hillside.

• The steel columns are inset from the exterior walls, removing the wood stud wall's typical need to serve as primary structure. This allows surround clerestory windows atop the stud walls for natural lighting and panoramic view windows.