Planting areas with restricted soil depth or restricted soil volume are notoriously prone to drying out quickly but don t be fooled into thinking you don t need to address drainage.
Grass depth of soil green roof.
Soil structure for green roof media.
This rooflite soil system supports lawn grasses that require deeper root space and thrive on a soil with plenty of finer particles and the precise amount of organic matter.
It is also important to factor in the type and lifetime of the roof membranethat will be used.
The structural engineer must factor in the weight of completely saturated soil since the plantings and the soil will hold a significant amount of water.
400cm3 green roof substrate weighed 800g 400cm3 garden soil weighed 1020g in other words around 20 more over a 100m2 green roof with 10cm depth of growing medium the weight saved by using substrate instead of soil is considerable.
Shrubs to one metre in height are best used in substrate depths of 250 mm or more.
Small shrubs provide cover display and habitat values and often form the bulk of plantings used on green roofs with deep substrates.
There are two types of green roof.
Rooftop lawns rooftop lawns are semi intensive green roofs with a total depth of at least 8 inches.
Green roofs or living roofs have become popular over the years.
The planting is just the tip of the iceberg underneath a moisture retention fleece keeps water in the soil rather than letting it pool on the membrane surface.
When designing a green roof there are several factors to take into consideration.
The lite system is typically used on retrofit projects when the roof is engineered with only 15 to 17 pounds per sf for the green roof component.
This is especially true of intensive green roofs which can have soil that is two feet deep or more.
This of course can be reflected in the cost of building materials.
Intensive roofs which are thicker with a minimum depth of 12 8 cm 5 1 16 in and can support a wider variety of plants but are heavier and require more maintenance and extensive roofs which are shallow ranging in depth from 2 cm 13 16 in to 12 7 cm 5 in lighter than intensive green roofs and require minimal maintenance.
Extensive green roofs these generally require a 5 15cm 2 6in depth of growing medium that can consist mainly of lightweight inorganic materials such as perlite leca sand rockwool and crushed tiles or concrete.
Green roofs with turf are lush usable spaces.
This is because they provide ecological benefits aesthetic value and creative urban architecture.
An aqua drain carries away excess water.
Increasing the substrate depth and irrigation will also increase the range of plants that can be used successfully.
Whether your planting bed is in the lawn green roof or a planter proper drainage is crucial.
Green roofs need to be installed on roofs pitched at no more than 30.
