Constraints of sloping roofs

realisation-forte-pente-hp-deauville-76-2The planting solutions for roofs described as being "steeply sloped" relate to pitches of over 20%. Today, developments in roof greening techniques mean that these sloping roofs can also be planted, even when the pitch is very steep. These highly visible steep green roofs form part of their environment thus allowing building owners to make the most of their building, showing, in practical terms, their sensitivity to plants and the environment. There can be multiple aims: low energy building (LEB), water management, preserving biodiversity or quite simply projecting a "green" image. There is no shortage of original architectural concepts for integrating the building into its landscaped environment. The resulting projects echo our countryside: many different pitches, rounded shapes, variety of colours and volumes.
Using planted systems on steep roofs is different from dealing with flat or gently sloping roofs. Specific problems are involved.

Preventing the risk of vegetation eroding

There is a greater risk of plants eroding in the establishment phase (before the plants start growing and send out roots into the growing medium). Planting techniques involving spreading seeds and planting plugs or pot-grown plants are not recommended for projects where the roofs are steeply sloping. Solutions which are pre-planted in the nursery are the most suitable as the plants start growing more quickly, and have an established root system to protect the soil from erosion.

Vegetal i.D. offers various planting solutions: the HYDROPACK® ready-to-install modular system and the i.D. MAT systems of multilayer planting with pre-planted mats. These solutions have been approved by a technical inspection service in a Specification for Installation Instructions for use on pitches of up to 200%.

Protecting the growing medium from eroding

In order to prevent the growing medium from eroding or slipping to the bottom of the pitch (mainly when there is a lot of storm water), barriers to prevent the growing medium from slipping must be installed for roofs whose pitch exceeds 20%.

Vegetal i.D. has developed various retention systems for steep green roofs: ACROPACK® systems, compatible with the HYDROPACK® all-in-one modular system and MULTIFIX retention systems, suitable for use with MULTICOUCHES solutions with i.D. MAT per-planted rolls. These systems have been approved by a technical inspection service in a Specification for Installation Instructions.

Compensating for the lack of water

In most cases, the water reserve of the planted system is greatly reduced with the pitch of the roof. This is why automatic watering is highly recommended.

Vegetal i.D. has developed watering solutions suitable for the pitch and system being used: water distribution will differ according to the systems used. In addition, the HYDROPACK® tray has a connecting water reservoir which facilitates and optimises satisfactory distribution of irrigation water over the roof.

Ensuring regular maintenance

A steeply sloping green roof requires regular maintenance to ensure that the plant cover lasts: weeding, checking the irrigation system, adding fertiliser. Aesthetic results can only be achieved if these tasks are carried out each year.

Vegetal i.D. offers a special maintenance contract for all projects for greening sloping roofs.

Performing a technical review of the project

A technical and bio-climatic project review is essential to determine the most suitable system for planting on steep pitches.

Technical and bio-climatic review -------> determine the planting system
direct environment
exposure and aspect
excess load 
roof structure
pitch of the roof
length of pitch
plant cover
planting system
anti-slip device
watering system


From erosion of the growing medium to increased requirements in water, sloping roofs present serious problems that oblige those involved to create innovative and effective technical solutions. Vegetal i.D. has developed the Vegetal i.D.® range of solutions for steep pitches, approved by a technical inspection service in a Specification for Installation Instructions for use on pitches of up to 200%. At the end of the spectrum Vegetal i.D.® solutions for facades allow planted systems to be attached to vertical surfaces completely safely.


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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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