Custom ADU Build in Diamond Bar: A Hillside Retreat Designed for Modern Living

When a property sits on a hillside, the possibilities for creating something exceptional multiply—if you have the right builder. This custom ground-up ADU by Ground to Gable Inc. is a perfect example: a beautifully designed secondary home nestled into the mountainside with panoramic views, seamless indoor-outdoor flow, and craftsmanship that honors both function and aesthetics.

Unlike most accessory dwelling units that begin with an existing structure or garage conversion, this project started with a blank slate. From grading and engineering to utilities, foundation, framing, interiors, and the expansive wraparound deck, Ground to Gable managed every detail in-house from day one.

Built Into the Landscape—By Design

Tucked naturally into the hillside, the ADU was engineered to work with the terrain, not against it. Ground to Gable created a stable foundation that supports the structure while preserving the beauty of the surrounding landscape. The result is a home that feels rooted, private, and intentionally placed.

Large windows and sliding doors capture sweeping views of mature trees and canyon ridges, instantly enlarging the living space and connecting the homeowner to nature.

A Wraparound Deck That Expands the Home

One of the standout features: the expansive wraparound patio that nearly doubles the usable living space. Designed for year-round enjoyment, it includes:

• Multiple seating and dining areas

• Thoughtfully selected composite decking for longevity

• Seamless transitions from interior to exterior

• Ample space for entertaining, relaxing, and taking in the mountain views

It’s the kind of outdoor living space that gives ADUs standalone-home energy.

Warm, Modern Interiors Designed for Comfort

Inside, the home blends warmth and modern functionality, with:

A beautiful neutral-toned kitchen

Featuring custom cabinetry, stone countertops, open shelving, stainless appliances, and a window wall that frames hillside greenery.

A spacious living room that opens fully to the deck

Wide sliders create effortless flow, making the interior feel airy and connected to the outdoors.

A spa-inspired bathroom

Soft tile tones, a glass-enclosed shower, upgraded fixtures, and thoughtful storage balance luxury with practical everyday living. Every finish was selected to complement the natural surroundings, giving the ADU a serene, elevated feel.

Designed for Independence, Built for Longevity

This ground-up ADU offers everything a homeowner could need—privacy, comfort, high-quality construction, and the flexibility to use the space as:

• A guest suite

• A rental unit

• A multigenerational living space

• A private retreat or home office

By starting from scratch, Ground to Gable ensured that the layout, flow, and structural integrity exceeded the standards of most typical ADU builds.

Thinking About Building an ADU?

We specialize in full-service design and construction for ADUs of every size—from garage conversions to hillside retreats like this one. If you're considering adding livable space, generating rental income, or creating a private guest house, our team is ready to help you explore what’s possible on your property.

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