Small Green Roofs: Ancaya Garden Shed

Enlarge Image Image Gallery "Small Green Roofs" focuses on small-scale and domestic green roofs and profiles more than 40 projects of all shapes and sizes, from green roofs on garden sheds and garages to houses and studios. Image Courtesy Timber Press

The following is an excerpt from Small Green Roofs by Nigel Dunnett, Dusty Gedge, John Little and Edmund C. Snodgrass (Timber Press, 2011). The excerpt is from the section Projects: Green Roofs on Sheds, Garden Offices, and Studios. 

Location: Raleigh, North Carolina
Owner and designer: Emilio and Kathryn Ancaya of Living Roofs, Inc.
Context: Private residential, garden building
Size: 8 × 10 ft
Main purpose of green roof: Reduce stormwater runoff, provide habitat for birds and pollinating insects, aesthetic

This new shed was part of the redesigned backyard landscape which included a fruit and vegetable garden, workshop, greenhouse, and green-roofed garden shed. Emilio and Kathryn Ancaya were in the process of redesigning their backyard and needed a garden shed, and they decided this would be a perfect place for a trial green roof. They knew the garden shed roof would be very visible from the house, so they wanted to integrate the building as best they could into the landscape. Additionally, they wanted to attract birds and pollinators to the roof.

Designing and planning 

Although they now own a green roof company, Emilio and Kathryn built the shed as their first green roof project, long before the company was formed. The experience was key to their discovery of the potential of green roofs. Emilio and Kathryn designed the structure themselves, based on information from Ed Snodgrass at Emory Knoll Farms, the internet, and various books. ‘The most challenging part was designing the drains. We came up with our own solution which works great,’ says Emilio.

Installation 

A standard waterproofing membrane was fixed to the roof. On top of this was placed a root barrier, a permeable landscape weed block fabric. Because the roof has a 7:12 (30°) slope, a wood grid system was used to keep the substrate on the roof. The grid was elevated 20 mm (0.75 in) above the roof surface to enable water to drain beneath. Substrate was laid to a depth of 10 cm (4 in) and was composed of a 4:1 mix of expanded shale and compost. Vegetation was introduced as plug or pot-grown plants grown by Emilio or obtained from Emory Knoll Farms and included species of Delosperma, Sedum, Talinum, Euphorbia, and Sempervivum. The roof is watered very occasionally using a garden hose, and an annual application of organic slow-release fertilizer is applied.