The faithful reader (follower) will have noticed the photos I’ve been uploading on our new shed which has an Extensive grass roof. The house we designed and constructed in 2004/6 also has a grass roof but instead is the Intensive version. But what are the two different types and what are the differences?

Let’s start with the roof to the house:

1. Intensive grass roof.

Below you can see the construction detail for the roof to the underground/lower section of our house:

The key features of an Intensive roof are the following:

• Deeper soil depths (normally 6-8″)
• Heavier loads on roof
• Require irrigation & drainage

These three key characteristics are all present in our Intensive roof, why?

• The roof was intended to always be of ‘traditional’ grass and an extension of the landscape around it, the grass seeds we sowed are identical to the grass fields that surround the roof
• The roof was intended to withstand substantial point loads from the likes of cattle & horses; this is why there’s a concrete deck
• The roof has concealed pipes that provide irrigation and drainage.

2. Extensive Grass roof.

In contrast we used an extensive grass roof on the shed. The key characteristics of an extensive grass roof are:

• Lower soil depths
• Lightweight
• Lower drainage and irrigation requirements

The detail below shows the roof we constructed for the shed roof:

The reasons for this choice were:

• The roof is higher with no likelihood of cows getting on top of it, hence the lower weight that allowed us to use a lightweight growing medium
• The then allowed us to choose suitable sedums that required lower drainage and irrigation requirements.

The sedums we chose came from GreenRoofsIreland and were grown on the shores of the Irish Sea, the system we used was the ‘Shed Green Roof System’ which was ordered and delivered online. So a special thank you to Green Roofs Direct for their excellent advice and lovely sedum.

The next post will show photos of the finished roofs and more details on the sedums…