Steep pitched green roof with HYDROPACK®

vegetated a steep pitch roof with HYDROPACK® highly sloped green roof with HYDROPACK®

Why choose the HYDROPACK® tray to green a steep roof?

  • System approved by a technical inspection service resulting in a Specification for Installation Instructions
  • Suitable for very steep roofs (up to 200%)
  • Easy to install
  • Patented, invisible anti-slip retention devices
  • No risk of the plants or the growing medium eroding

A technical review of the project is essential

It is essential to conduct a technical review of a planting project on a steeply pitched roof in order to limit the risks of erosion and to recommend the most appropriate retention device and watering system. The Vegetal i.D. team of engineers provides expertise and technical assistance throughout the project, especially in the following stages:

  • Determining the plant cover, the planting system appropriate for the project and the load effect to be taken into account (pilot-study phase);
  • Study for designing the right planting system for the project, working out the sizes of the anti-erosion and retention devices (design phase);
  • Determining the loads associated with the plants and retention devices for establishing the dimensions of the load-bearing component;
  • Laying the planting system;
  • Maintaining the planting system.

Description of the HYDROPACK® steep slope system

Caractéristiques principales du système  HYDROPACK® conçu par Le Prieuré
The HYDROPACK® tray brings together in one module all the components of the multilayer planting systems (drainage, filter, growing medium, and plants).

The HYDROPACK® tray water reservoir

la dalle pré-cultivée HYDROPACK® conçue par Le  Prieuré

The numerous compartments located at the bottom of the tray allow a permanent water reservoir to be created, beneficial for growing plants, as well as for retaining rainwater on the roof. The trays are perforated (500 holes/m2) at the top of the compartments, i.e. at a height of 30 mm above the waterproofing membrane. So, once the compartments have been filled, the excess water joins the channels for draining water to the RWI (rain water inlet) points.

HYDROPACK® suitable for very steep roofs

The all-in-one format of the HYDROPACK® tray is particularly well suited to projects for greening steep roofs where using multilayer solutions can be complicated. The HYDROPACK® tray avoids erosion of the growing medium and the vegetation: its walls create a partition between the growing medium and the vegetation, and the plants which have been grown previously in the nursery for 8 months, are firmly rooted in over the whole depth of the planted system. So there is no risk of the growing medium and the vegetation eroding when it is installed.

Specification for Installation Instructions for the HYDROPACK® tray was issued after the system was approved by a Technical Inspection Service.


Innovative and patented retention systems: ACROPACK®

 HYDROPACK® et solution anti-glissement ACROPACK® sur une toiture en très  forte pente There are three innovative retention systems for retaining HYDROPACK® trays on steep roofs: ACROPACK® T, ACROPACK® Ω and ACROPACK® L. The Vegetal i.D. engineering team selects the retention components according to the project's characteristics. Developed by Vegetal i.D. (and patented), ACROPACK® anti-slip solutions stop the HYDROPACK® trays from slipping on steep roofs and interlink perfectly under the HYDROPACK® trays; this means that the water can flow from tray to tray. The ACROPACK® Ω and ACROPACK® L retention systems are completely invisible (the surface of the struts in the ACROPACK® T solution do not permeate the membrane). The number of anti-slip devices in the HYDROPACK® solution is lower than that required for a multilayer system: the way the trays are partitioned off means that retention devices can be eliminated, the number of holes in the waterproofing membrane is reduced and in this way the plant system can be laid more easily on the sloping roof.coupe-type-acropack la dalle pré-cultivée HYDROPACK® et solution  anti-glissement ACROPACK®HYDROPACK® and ACROPACK® anti-slip system

Special watering solutions

The HYDROPACK® tray has a connecting water reservoir which facilitates and optimises satisfactory distribution of irrigation water over the roof. This water reservoir is complemented by the installation of an irrigation system.
Each planted zone on the roof must have a water connection whose output is suitable for the surface area of the roof.

Vegetal i.D. has developed watering solutions to suit every type of surface, whether flat or pitched, as well as aesthetic expectations. These devices are perfectly placed among the plants so they are difficult to see.

Installation of HYDROPACK® sloping system

Installation of ACROPACK® retention device

la dalle pré-cultivée HYDROPACK® et solution anti-glissement  ACROPACK® Installation of ACROPACK® T retention devices, positioning with empty HYDROPACK® trays

The ACROPACK® anti-slip retention devices are fixed to the load-bearing component, or even to the load-bearing structure, through the layers of waterproofing and insulation installed by the waterproofing company. They are arranged perpendicularly to the pitch. The ACROPACK® anti-slip retention devices have been designed to make sure that the seal is not broken around the fixing devices.

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 finished either by a curb with flashing, or a runner with an overhanging gutter.

Installation of HYDROPACK® trays

hydropack-en-pente Direction of installing the HYDROPACK® trays to allow water to flow from one tray to another

The HYDROPACK® trays are placed on the waterproofing membrane after installing the retention systems. They are fixed to each other using hooking systems arranged around the outside edge of the trays. The trays are installed from right to left and from bottom to top. The second line is placed immediately above the first one, and so on. The trays must only be positioned horizontally (longer length perpendicular to the pitch) and with the male attachments pointing downwards in order to respect the water’s direction of flow. The HYDROPACK® trays can be cut to follow the shape of the roof.

No vegetation zone

If the HYDROPACK® system is used for planting an area, no separation device between the trays and the no vegetation zone is required. The no vegetation zones can be eliminated under certain conditions (see Professional Regulations). Nevertheless the area around the rainwater inlets (RWI) must be kept clear by creating a no vegetation zone of at least 40 cm wide.


The HYDROPACK® planting process on a steep roof can be installed either directly by the roofing contractor, or, with the latter still retaining responsibility, one of the roofing contractor’s co-contractors or subcontractors (which may be a landscaping company).
Vegetal i.D. can then install the system.

hydropack-acropack-omega Positioning HYDROPACK® trays on ACROPACK® Ω retention device

The choice of the method of fixing the retention devices to the load-bearing component, as well as determining its dimensions to comply with the loads applied is the responsibility of the waterproofing company. It is the job of the waterproofing company to fit the retention devices to the load-bearing component. The company supplying the roof framework must determine all the loads to be taken into account and the dimensions of the load-bearing component. These loads are made up of permanent loads, working loads and 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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