Green Roofing San Diego

by Paul Tilley, Shasta Landscaping

Shasta Landscaping, Inc. created a 5,300 square foot green roof for the Charles David Keeling Apartments at the University of California, San Diego. They built a recycled-water irrigation system to feed the 4,000 plants.

This San Diego, California, Shasta Landscaping, Inc. green roof project at the Charles David Keeling Apartments at University of California, San Diego, challenged Shasta Landscaping to create a "ground up" green roof project that included installing a recycled water system and planting more than 4,000 drought tolerant succulents, flowering plants and low-spreading shrubs.

Measuring 5,300 square feet, the green roof was created to achieve multiple goals, including reducing its carbon footprint, saving energy, and providing a visually appealing place for the university's students to visit.
The project took Shasta three months and 25 workers, including prepping and waterproofing the roof surface, running a recycled gray water irrigation system and finally planting.

Step 1: The first step was to clean off the entire 5,300 square foot roof surface to prevent any damage to the membrane. Workers applied a water-based bonding adhesive, then laid down the MMB (membrane) material. Finally, they fused the membrane seams together using a hot-air welding method.

Installation
Their first step after cleaning the roof surface was to apply a water-based bonding adhesive. Then workers installed 5,300 square feet of MMB (membrane) material. They fused the membrane seams together using a hot–air welding method. Following this, a 30-millimeter thick polyethylene root barrier liner was laid down over the MMB. They overlapped its seams and created waterproof seals with Butyl tape. Drainage mats and panels came next, followed by planting boxes.

Step 2: It took the crew one day to install a 30-millimeter thick Virgin-blended polyethylene root barrier liner. They laid the root barrier flat over the MMB, but did not attach it directly. The seams were overlapped 12 inches and a single-sided BUTYL Tape was used to create a waterproof seal.

Once the planters were built, it was time to install planting backfill and shrubs. The company chose Green Roof solution green roof product, as well as soil mix from Gail Material. Next, workers installed the decorative rock, mulch and the irrigation system. Shasta planted more than 4,000 drought tolerant succulents, flowering plants and low-spreading shrubs like English Stonecrop, Reflexed Stonecrop and Snow-in-Summer. Shasta listed the project budget, a tight installation timeframe, and transporting materials six stories up to the roof as its major challenges.

Step 3: The next step was to cover any and all exposed membrane and root barrier with a moisture mat (MRM-30). Workers installed the MRM-30 to protect the (MMB) from the edge retainer. Since the aluminum edge retainer will expand and contract with daily temperature fluctuations, the MRM-30 acts as a buffer. The MMB was also used to seal up any pipe or other fixture that penetrates the roof.

Plant Material
Shasta divided the 5,300 square-foot area into four separate mix zones. Mix A, planted in the back portion of the project, was made up of 112 4-inch pots of bulbine frutscena, 100 4-inch pots of sedum refleum 'Blue Spruce', sedum confusum, and 168 4-inch pots of sedum gold. Mix B, in the next plot area, consists of 339 4-inch pots of Dudley Brittonii, 265 4-inch pots of Echeveria Elegans 'Super Clone', and 185 4-inch pots of Echeveria 'Afterglow'. For Mix C, Shasta planted 432 4-inch pots of Bouteloua Gracili, 184 4-inch pots of Cerastium Tomentosum, 86 1-gallon Salvia Chamaedryoides, and 57 1-gallon Salvia Mellifera. Finally, for Mix D, they planted 142 4-inch pots of Echeveria 'Perle Von Nurnberg', 183 4-inch pots of Sedum Rubrotinctum 'Pork n Beans' and 167 4-inch pots of Sedum Spurium.

Step 4: Following the MRM-30 installation, the contractor installed the .125-inch thick aluminum, 12-17-inch edge retainer and 7-inch leveling strip. They filled the area with growing media (soil), and added rock to the remaining space.

Recycled Irrigation
Additionally, all the water used for the roof garden is recycled on site and plumbed for irrigation, along with all residents' water from laundry, sinks and showers.

Step 5: Next came the installation of 1,090 24x24-inch drainage panels. The first step was the drainage layer (GRS-52), which will help drain water from rainfall and irrigation, under the medium. Water is collected through the roof drains, which connect to a holding tank built in the foundation of the building. Numerous filters and pumps clean the water and send it into to the irrigation system that supplies the roof and all the ground floor landscaping. The plumbing was installed as reclaim (purple pipe). Pumps where installed by the building plumber.

Award Season
Shasta Landscaping, Inc. was awarded the President's Award by the California Landscape Contractors Association (CLCA) for the project.

Step 6: 5,300 square feet of filter fabric was installed, to keep soil from entering the drainage panels. The contractor used more than 250 cubic yards of Soil Medium, which consisted of 40 percent 1/8-inch Planting Humus compost, 45 percent 3/16-inch Scoria/lava rock and 15 percent washed concrete sand. The material was staged at the bottom of the street, then craned to the top using 1-yard concrete bins.

Step 7: Next, workers poured in more than 80 cubic yards of Lava rock and media, which was craned to the roof. For irrigation, the company installed more than 3,500 linear feet of drip-line tubing.

Step 8: The last step was planting the green roof material. It took a 5-man crew four days to plant the entire garden.

Strips of tan 1-2-inch decorative rock were used at drain locations. Workers poured in more than two cubic yards of rock in these areas.