Green Roof Substrate - 25kg bags x 40

Green Roof Growing Medium

A high quality lightweight green roof growing medium for extensive green roofs. The green roof substrate is general purpose, containing all the nutrients required to support everything from wildflowers to sedum blankets. It is suitable for both commercial and domestic roofs.

Our green roof substrate contains a combination of topsoil made from green waste compost along with sustainable aggregates. It will help you grow and maintain a beautiful green roof that attracts wildlife and delivers a range of benefits. Remember that garden soil is not suitable for green roofs.   

We offer a full pallet of 40 x 25kg sacks - An 80mm depth of growing medium is the minimum suggested depth, as per the Green Roof Code of Best Practice for the UK 2021. This full pallet quantity will cover an area of approximately 18m² at 80mm depth.

Uses of growing substrate

This green roof growing medium is suitable for the following:  

• Substrate for sedum blanket and wildflower matting or seeds 
• Extensive biodiverse roofs
• For planters

Green roof substrate composition              

The green roof substrate composition is a combination of specially graded expanded clay aggregates and compost. We have focussed on sustainability in its production. The expanded clay aggregate is mixed with crushed aircrete blocks that are damaged and can no longer be used in house building. These are then crushed to our specification making them ideal as a green roof growing media. The green waste compost is from horticultural wastes collected during municipal works, such as hedge trimmings.

The growing medium is specially designed to support wildflowers and sedum on an extensive green roof. It has the following attributes:        

• pH value: 8.5
• Total pore volume: 52 - 60%
• Soil Organic Matter (SOM): 5.0%
• Maximum water holding capacity 41% vol 

Installing green roof substrate 

The green roof substrate comes in bags on a pallet. Once you have completed the green roof system with a waterproofing layer, root barrier, and drainage membrane as required you are now in a position to add the growing medium.

IMPORTANT NOTE: Make sure your roof structure can take the weight of the growing medium and build-up. 

You need to empty each sack onto your roof and spread it carefully to a recommended depth of 80mm. Permagard supplies pallets with enough substrate for an 18m² roof at 80mm depth (40 x 25kg sacks). Rake out to the required depth, taking care around protrusions. Protrusions such as skylights, drainage pipes etc. will generally require a separation layer of pebbles with a length of geotextile fabric between the pebbles and growing medium/vegetation. This is to ensure that soil fines and roots don’t clog around the protrusions. 

To contain your growing medium, protect protrusions and ensure effective drainage, you should consider some or all of the following:

• Geotextile edging strips
• Aluminium edging trims & connectors
• Perimeter pebbles
• Reinforcing roofing scrim

Permagard - Providing Solutions. Inspiring Confidence.

As a green roof substrate supplier, we focus on sustainability and quality. Our green roof growing medium is reliable, lightweight and with all the required nutrients. It is a vital part of our Green roof systems and an add on to our simple green roof kit. If you have any questions about your specification or need more substrate than listed here, we can help. Call our expert team. Read our Green Roof Construction Guide for more technical details or our introduction to green roofs for more information.