Green roof FAQs

How easy is it to install a Green Roof?

The green roof package is designed to be a simple system that is easy to install above the waterproof membrane. The green roof package can be installed on flat roofs and on pitched roofs up to 30 degrees without additional irrigation. Slopes of over 10 degrees may require additional slope stabilisation measures to avoid slippage of substrate and may require additional anchoring of the vegetation layer. We can supply slope stabilisation options if required.

What are the Green Roof depths and loading weights?

Green roofs have a depth of 105-155mm and a saturated weight of approximately 85-135kg per square metre depending on substrate depth – for example:

The Vegetation layer is 25mm 25kg/m2 fully saturated, Roof drain drainage is 30mm 10kg/m2 fully saturated layer Extensive green 75mm 75kg/m2 fully saturated roof substrate TOTAL 130mm 110kg/m2 loading deep

Can I put a green roof onto an existing building?

We recommend all buildings with a green roof are fully compliant with building regulations.

Can I use soil or compost instead of substrate?

Our Substrate is an extremely lightweight material designed specifically for the green roof to provide the correct level of nutrient and saturated weights. If other materials are used the saturated weight must be considered along with the correct nutrients for the vegetation layer.

Will the green roof be waterproof?

A waterproof membrane must be fitted before our green roof is installed. For further information on where to purchase the correct waterproof membrane please contact our office.

Do I need to water my green roof?

Initial watering must take place until the vegetation layer is established. Once established there will be no need for irrigation except in extreme prolonged drought or where the aesthetic value in dry periods is important.

Roofdrain 25 acts as a water reservoir holding an additional 5.3 litres of water per square metre to further reduce the runoff from the roof. This stored water can be released slowly, used as grey water or even used as irrigation for the vegetation mat.

What maintenance is involved?

Most green roofs require some annual maintenance. The Wildflower & Sedum mat requires one cut in the autumn with all cuttings removed. SedumPlus will need occasional hand weeding to remove plants from windblown seeds.