With the news that Enviromat has reduced the price of sedum matting by almost 20%, Angela Lambert looks at the cost of putting a green roof on your shed.

A beautiful sedum roof is a lovely adornment for any sturdy building and it’s easy to install once you know how, but the bottom line, when making any decision involving an investment in the environment is, what will it cost?

Let’s look at a typical garden office with a footprint of 10 feet by 8 feet.   We’ll assume that it’s a strong building with a very slight pitch to the roof and that all the waterproofing is in place.  That means that there are no structural changes to be made such as strengthening.

Green roof edgings

First up, edgings:   These are a matter of taste and so price is variable.  Save money by using reclaimed timber or make a statement by commissioning some bespoke edgings. – more about this in another blogpost

Green roof build-up

First determine the area by multiplying the width of the roof by the length.  Use the online area calculator at http://www.enviromat.co.uk/enviromat/ if you’re unsure – it also has a helpful ability to convert imperial measurements to metric ones.

Our 10ft x 8ft shed has a roof area of 8 square metres.

Because it has a roof slope of less than 3 degrees, it needs four layers of material in the green roof build up;

Polyethene to protect the waterproofing against damage from roots or boots

Drainage mat to ensure the sedum plants don’t languish in conditions that are too wet for them

Water retention mat to support the plants when rainfall is in short supply

Sedum matting. – the bit with the plants in.

Putting 8 square metres of each of the products above, into the Enviromat online shopping trolley, along with a tub of green roof feed, gives a TOTAL price including VAT and delivery of £412.08

Please note, this price is correct at the time of writing (29th April 2012 and is for delivery to a Bristol postcode) Prices will vary depending on delivery area and are considerably less if you collect from either of our farms.

Cost of the green roof build up for a 10×8 flat roof is less than £420.00

Enviromat offer discounts on large areas and for trade customers.