characteristics

Soil Depth: Approximately 6″
Module Size (plastic): 1′ x 2′ x 3-¼”
Saturated Weight: Approximately 40-50 lbs per square foot
Dry Weight: Approximately 30 pounds per square foot*

What it is

The Deep System is used for biodiverse green roofs. With 6 inch soil depth it becomes possible to support a broad array of non-succulent plants. One can literally create a prairie or shade garden on the roof. Naturally the weight is greater, appx. 40-50 pounds per square foot, depending upon soil and plants, but the weight is not so heavy as to greatly drive up the cost of the supporting structure.

What it does

It is primarily used for biodiversity, prairies and garden-like perennial plantings. It also allows for food growing and shade planting, on roofs that are too shady for succulent plants. The Deep System is excellent for saving energy, good for storm water management, and easily meets most green space requirements.

Because it can support a broad array of plants, it can provide habitat and food for pollinators such as butterflies and honeybees and various bird species. Plantings can be random and naturalistic as well as patterned. The Deep System also seamlessly transitions to the Standard or Maxx System without need for edging in between.

What plants work

The type of plants used in the Deep System include a full array of low to tall growing Sedums, hundreds of different fibrous rooted herbaceous perennials, including native forbs, sedges, grasses and edible plants. But, one should avoid plants with woody root systems such as shrubs, as they can damage waterproofing. Foliage colors can vary widely; green, yellow, red, purple and blue are possible, and flowers of any color and shape are found within the broad palette of plants capable of growing in its 6 inch soil profile.

How it looks

Its appearance is determined by plant selection, and often the plants are arranged in naturalistic sweeps or planted randomly when creating prairie habitat. And, because roofs are often windy, grasses are commonly employed for an added element of motion.

What it needs

You might think that with 6 inches of soil, the Deep System would have tremendous water holding capacity, and it does. However, the plants that are used are typically not the type that store water, like the succulents used in the thinner soil profiles. Therefore, whenever the Deep System is used, one must include a built-in spray rotor irrigation system in the design. Spray rotor heads should be used, as (in the gravelly soils used for green roofs) they use considerably less water than drip or sub irrigation methods. Irrigation frequency will vary with climate and plant types, but in general it will need irrigation every 3 or 4 days during the summer months.

Maintenance is more involved than with the other systems, but less than traditional landscape plantings as LiveRoof soil is not full of weed seeds like typical topsoil.

How it’s grown

Many designers prefer to include a base layer of succulent Sedums, as a living mulch, in conjunction with the core accent plants, which are planted from plugs and grown on at the nursery until well-rooted. It is important to provide plenty of advance notice to your LiveRoof grower if any uncommon species or quantities are needed. Grow time ranges from approximately 10 to 16 weeks depending upon climate and plant selections.

Comparative cost

The Deep System is more costly than the Standard System because of the soil depth, plant types, and relatively longer installation time. But, like the other systems it is a remarkable investment that pays off with energy savings, extension of the roof life, beauty, code compliance, quality of life, and so much more.