How to specify Green Roofs [CHECKLIST]

How to specify Green Roofs [CHECKLIST]

Make sure you don't miss anything whilst specifying your Green Roof System by using our handy checklist:

Check your roof is suitable: green roofs require a roof pitched at no more than 30° and some types of living roofs require concrete roof decks.

What is the maximum load baring capacity?: the water saturated weight of the roof including vegetation must be calculated as permanent load so first ensure your roof can hold the weight of your green roof system

Decide what kind of green roof you require:
•Intensive green roofs require thick soil and regular maintenance – new builds.
•Extensive green roofs are shallow with low-growing vegetation, require little maintenance – retrofit or new build.
•Semi-extensive green roofs have a slightly thicker layer and offer greater plant diversity – possible on some retrofit projects.

Choose the correct waterproofing; the waterproofing needs to be robust and root-resistant. In specifying waterproofing for a green roof take into consideration density and tensile strength. You will also require a protection layer on the roof surface, such as a puncture-resistant geotextile.

Drainage: drainage is important to consider in specifying a green roof, sturdier roofs can use a layer of gravel or plastic drainage layers and cockleshell layers can be used as more lightweight alternatives. A filter sheet should be installed above the drainage layer to stop soils washing out. Guttering must also be considered.

Do you have roof insulation?: All types of green roof systems can be installed over non-heated rooms such as garages, where insulated roofs are concerned the thermal insulation must show sufficient compression resistance and a vapour barrier should be installed.

Choose your plants: ideally small plants are better for a green roof, especially ones with smaller leaf areas which means they are less susceptible to water stress and tend to respond better to green roof conditions. Natural climate and wind conditions should also be taken in to account as well as the level of maintenance a plant requires.

How will you maintain your green roof?: Include access points in your initial design as the green roof will need maintenance and service during its lifespan.

Click here for more Green Roof resources on the Green Roofs Hub

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