Steep pitched green roof with i.D. MAT

Why choose Vegetal i.D.® multilayer solutions with i.D MAT mats to green a steep roof?

  • Particularly well-suited to non-standard projects
  • Wide range of plants
  • System approved by a technical inspection service which is the subject of a Specification for Installation Instructions




Description of Vegetal i.D.® multilayer systems with i.D. MAT sedum mats

Depending on the projects involved, Vegetal i.D.® multilayer systems for steep pitches with iD MAT mats generally consist of the following elements:

  1. Drainage layerDrainage makes it easier for water to escape and thus avoid excess water in the growing medium.
  2. Water distribution mat or filter
    The water distribution mat retains additional water and distributes water in a better way over the surface of the system. When installed it optimises water resources, by lengthening the period between watering. The filter prevents the fine particles contained in the growing medium migrating to the rainwater drains.
  3. Growing medium
    The Vegetal i.D. i.D. FLORE range has various formulae for growing medium, which combine properties of permeability and aeration with those of water retention, in a stable and long-lasting way. i.D. FLORE growing media consist of high-quality natural mineral and organic materials, selected for their physical characteristics and their durability. All i.D. FLORE growing media possess physical and chemical characteristics, which comply with the Professional Regulations and German FLL standards. For each project, the choice of growing medium type and depth is made to suit the plant cover, the geographical location, the exposure, aspect and pitch of the roof. The choice ranges from growing media, which retain a large quantity of water to substrates with very high drainage qualities that are specially suited to situations with persistent humidity.
  4. Plant layer
    i.D. MAT sedum mats are pre-planted in the nursery in order to provide plant cover of 70 % minimum. They contain an organic frame which gives them structure and cohesion.
  5. Anti-erosion and anti-slip device

There are three systems to retain i.D. MAT mats on steep roofs: MULTIFIX T, MULTIFIX 3D and MULTIFIX L.

iD mat and MULTIFIX 3D anti-slip solution on an extremely steep roof Deployment and installation of the MULTIFIX 3D cellular network

MULTIFIX technical and innovative solutions, developed by Vegetal i.D., stop the planting system on steep roofs from being eroded and slipping. The Vegetal i.D. engineering team selects the elements comprising the planted system depending on the nature of the project. Above a pitch of 100%, a special project study is required in relation to growing medium retention and satisfactory irrigation of the system. i.D. MAT RENFORCÉ is recommended for long slopes and pitches in excess of 35% as it has an additional solid polyester frame.

Vegetal i.D. solutions for steep pitches with i.D. MAT pre-planted sedum mats have been approved by a technical inspection service in a Specification for Installation Instructions for use on pitches of up to 200%.

Special irrigation solutions

In most locations, watering using an automatic irrigation system is recommended for pitched green roofs. The pitch actually makes the vegetation very sensitive to dry periods by increasing the effects of solar rays, reducing water retention through drainage and reducing the input of natural resources (smaller surface impacted by rain). Each planted zone on the roof must have a water connection of the correct size in relation to the surface of the roof.

The Vegetal i.D. engineering team carries out a technical review and determines the most suitable watering solution for the pitched roof project in order to obtain optimum plant cover and the most effective irrigation system which is as unobtrusive as possible.

Installation of Vegetal i.D.® multilayer system for a steep pitch

Installation of MULTIFIX® retention device

Installation of growing medium with MULTIFIX T retention devicesThe MULTIFIX® retention devices are fixed to the load-bearing component, or even to the load-bearing structure, through the layers of waterproofing and insulation. They have been designed to prevent the seal being broken around their fixing systems

Installation of a retention device at the bottom of the pitch

A retention device is systematically put in place at the bottom of the pitch. It consists of an openwork retention device. The bottom of the pitch can be created either by a curb with flashing, or a runner with an overhanging gutter.

Installing the planting system

The various layers making up the MULTICOUCHES Steep Slope vegetating solution using i.D. MAT sedum mats are installed in the following order:

  • The drainage layer: recommended for roofs with pitches in excess of 20%, this is rolled out directly on the waterproof covering.
  • The water distribution mat or filter
  • The growing medium
  • The vegetation: the i.D. MAT sedum mats are rolled out directly onto the growing medium.

They can be installed throughout most of the year (frosty periods and high summer temperatures must be avoided). After the sedum mats have been laid they must be watered in order to wet the growing medium under the mat. Watering will be repeated while the plants are rooting themselves into the mats unless there is sufficient rain in terms of quantity and regularity. The sedum mats must not dry out during this period.

Installation of the vegetation free zone barrier

amenagement zone-sterile-pente

In the case of planting involving a Vegetal i.D.® multilayer system, it is essential for a separation device to be positioned between the planted zone and each sterile zone. The height of the device must be greater than the total thickness of the planted system and it must have an openwork design to avoid impeding the flow of rainwater. Then it must be covered with a filtering layer to avoid particles of growing medium flowing through openwork areas. In the absence of a filtering layer in the main part, a filter must be installed alongside the separation devices over their entire depth and under the substrate to a width of 2 m.


The Vegetal i.D.® multilayer planting process by using an i.D. MAT sedum mat on a steep roof can be installed either directly by the roofing contractor or, with the latter still retaining responsibility, or one of the roofing contractor's co-contractors or subcontractors (which may be a landscaping company).
Vegetal i.D. can then install the system. The choice of the method of fixing the retention devices to the load-bearing component, as well as ensuring that its size complies with the loads applied is the responsibility of the waterproofing company. It is the job of the waterproofing contractor to fit the retention devices to the load-bearing component. Determining all the loads to be taken into account and the dimensions of the load-bearing component is the responsibility of the company providing the roof frame. These loads constitute permanent loads, working loads, as well as their weightings. When retention devices are used it is difficult to calculate snow load and this must be the subject of a special study to be conducted by the company responsible for the roof framework.

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adivet association des toitures végétalesGreen Roofs for healthy city associationPole Dream, Pole de compétitivité eaux et milieux - région Centre

VEGETAL i.D. designs and produces innovative,useful green solutions that integrate into urban andsuburban environments to make cities more pleasant,environmentally sound and smarter places to live.

A bespoke VEGETAL i.D solution exists for each urban greening project : flat or sloped roofs, biodiverse or biosolar roofs , urban farming , indoor or outdoor living walls , podium decks design with integrated sotrmwater management

Contact VEGETAL i.D engineering board to help you design your project

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