Green Roof Methods
Modular, Mats, and Built-Up Planting Methods for Green Roofs
There are a variety of ways to install plants on a green roof. No matter the method, the initial steps are the same. The roof is carefully waterproofed, root barriers, irrigation, drainage and rooftop infrastructure are installed and then the plants are either set in place or planted. Modular and mat systems offer instant green because they’ve been grown offsite. The built up method allows for greater flexibility in design and plant choice, but take a little longer to look like a green roof.
Modular – A modular system usually combines several of the green roof’s layers into pre-manufactured and often pre-planted systems that are placed directly on a roof that has been prepared with a proper water proofing membrane. There are a number of manufacturers of green-roof modules allowing for choices in size, weight and plant variety. A modular green roof allows for fairly easy alterations and additions, instant green and easy access to the roof surface below. Modular systems are frequently used on extensive portions of a green roof.
Mats – Like the modular systems described above, the mat method uses green roof plantings grown off site and later installed on the green roof after proper waterproofing has occured. Mats are laid much like a carpet or grass sod. They are placed on the roof to provide complete coverage, and often instant green. Over time, mats will grow together, seams will disappear, and with proper care, a solid looking green roof will appear. Mats are frequently used on extensive portions of a green roof.
Built-Up – This type of green roof allows for greater flexibility in design and plant choice. After installing proper water proofing and root barriers and building the designed rooftop infrastructure, such as planter boxes, irrigation, pathways, cisterns, and trellises, the planting medium is spread on the roof, and then plants are added. This is often called “planting in place.” It may take a while for a green roof planted in place to look lush and green. The built-up method is used most often in planting intensive and hybrid green roofs.