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Green Roof installation
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It is worth noting that before you undertake any green roof project, that you ensure that the structure of the roof is sufficiently strong to take the extra weight. Any calculations must also take into account the weight of water that will be held in the soil. If the roof is a new build it should have a fall of at least 1:50 (this equates to 20mm fall for every meter travelled) towards the water outlet or guttering. This is recommended as a minimum, a greater fall is desirable. Tips on roof construction can be found on How to build a Flat roof. After you have installed the EPDM roof as described with step by step instructions on the EPDM installation page, it is then a simple step to install a green roof on top, the following should be adapted to suit the your requirements. For roofs with small or insufficient upstands the construction of a confinement frame will need to be constructed, this should be built using a suitable long lasting timber we used tanalised timber as a cheaper option to prevent premature rot but this choice is up to you if you have the budget use hard wood. The frame should be high enough to accommodate all the necessary contents this is dependant on the type of green roof being constructed and it's eventual use. The frame should be laid on the roof with edge facing the drainage (i.e. the edge facing the drain or drip edge.) being packed up by 10 - 20mm to allow sufficient drainage. Geotextile should then be laid in the bottom of the frame over the entire area, a layer of rounded washed gravel (river gravel), clay granulates or similar should then be laid to assist with drainage, Another layer of geotextile or any other rot resistant fleece with a high tear strength and perforation resistance is then laid over the drainage layer to stop it silting up. Applying the soil layer is the next operation the thickness will be determined by the use that is to be made of it i.e. the deeper the roots of the plants then the thicker the soil needs to be. All that remains is to plant up the area. This is worth serious thought before planting, taking into account speed of growth, need for maintenance, watering, feeding etc. If you are installing a Sod or Sedum layer over the roof then most of the above can be disregarded except for the geotextile that is laid directly onto the EPDM which will now perform a different function than that above as the roots will grab the geotextile to create a strong mat of vegetation.
Although these pages are checked regularly and every care is taken with the information within. Delston can not accept any responsibility or liability for information or results displayed within due to third party interference. All information was deemed correct at time of publication. Author Myrddin
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