Project Team
Green Roof Design, Construction & Maintenance: Living Roofs, Inc.
Architect: in situ studio
Plant Nursery: Hoffman Nursery
Arbutus Secret Garden
The project transforms an otherwise underutilized residential rooftop in Raleigh, North Carolina, into a high-functioning green roof inspired by the region’s native Piedmont prairie ecosystem. Despite its compact footprint and challenging conditions, ranging from deep shade to intense direct sunlight, the design creates a dense, diverse planting community with year-round visual interest and ecological value. Lightweight geofoam was used beneath the growing media to create gentle contours and undulating topography that echo the rolling hills of the Piedmont without adding significant structural weight.
A six-inch growing media layer and high-density planting help capture and retain rainfall, reduce runoff volumes, and delay peak flows into the municipal stormwater system. This is particularly valuable given the project's location within the flood-prone Crabtree Creek Watershed. A smart irrigation strategy combines a permanent drip system with a temporary overhead micro-spray system for plant establishment, while an integrated rain sensor prevents unnecessary watering during and after precipitation. The green roof also contributes to energy efficiency by shading the home, reducing heat transfer, and cooling the building through evapotranspiration. Alongside a rooftop solar photovoltaic system, it helps reduce the home's energy demands and reliance on the municipal grid.
The carefully selected mix of native and well-adapted grasses, ferns, and other plant species creates habitat for local pollinators, birds, and beneficial insects. Dense planting provides food, shelter, and nesting opportunities, while the roof's seasonal changes in colour, texture, and movement contribute to its visual character. The garden is also integrated into the home's interior through views from the second-floor primary bedroom, an oculus at the entrance, and the kitchen. These everyday connections to nature support occupant well-being, while the growing media and vegetation provide acoustic buffering, filter particulate matter, and help cool the surrounding microclimate.
Sustainability is carried through the project's material sourcing, construction, and maintenance. Key components, including growing media, drainage mat, slate chips, and plant material, were regionally sourced to reduce transportation emissions and support the local economy. The green roof designer, installer, and maintenance company are certified Living Wage Employers. Maintenance follows a zero-pesticide approach, with monthly visits during the growing season, annual soil testing, and irrigation adjustments based on seasonal conditions. Organic matter, including seedheads and standing stalks, is left in place through the winter to provide food and nesting structures for wildlife while naturally returning nutrients to the growing media. No fertilizer has been required to date.
The project was shaped by close collaboration between the client, architect, and a specialized team of green roof professionals, from early design through construction and ongoing ecological monitoring. Custom-fabricated edging, carefully designed planting layouts, and the integration of functional roof components into the overall aesthetic give the garden a distinct sense of place. Envisioned as a forest glade within the surrounding tree canopy, the green roof responds to the home's architecture and natural setting. Although a private residential installation, it demonstrates how a relatively small rooftop can contribute to stormwater management, urban biodiversity, watershed protection, and climate resilience, offering a model for integrating green infrastructure into residential design.
