How to make a timber edge for your green roof

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Unless you’re lucky enough to have a raised parapet around you green roof you will need to install some kind of edging.  Here’s how to make green roof edging using timber.

timber edging on sedum green roof shed

A timber green roof edging is in keeping with wooden sheds, shepherd huts and summer houses and is easy to build yourself with just a few DIY skills

Why does your green roof need edging?

Green roof edging gives a neat finish to the project. Not only that, it helps manage drainage and stop wind damage.  Remember all of those components that make a green roof successful? Something’s got to stop them from tumbling off the roof – that’s the third main function of the edging.

Why choose timber edging?

It is possible to buy commercially produced aluminium edging for green roofs.  These edgings do the job perfectly – but they’re designed to be functional not pretty.

metal green roof edging

Specially engineered green roof edging is widely available to buy online. 

If you have a beautiful timber building – maybe a summer house or a traditionally built log store – you need an edging that’s in keeping with the rest of the structure.  Sometimes, only wood can give the effect you need.

How to make your timber edging

It’s easiest to put the edging on before installing the rest of the green roof.

Make sure that the roof is entirely waterproof before you start.  You’ll be pretty miffed if you finish the edging and then need to take it down to make changes.

Your roof will need an escape route for rainwater so the first thing to do is put some spacers between the eaves and the edging.

Fix 20mm thick blocks of wood at intervals along the edge of the roof. 

If you’re using nails or screws, be careful to only pierce the waterproofing where it wraps under the eaves – don’t go putting holes in the top of the roof.

A length of wooden edging can then be fixed to the front of these blocks.  This is the bit that will be visible so be as creative as you like with the shape of bottom edge.  It’s a good idea to buy pressure treated wood because it’s going to have damp vegetation pressing against it 24/7.

The top of the edging needs extend above the roof deck by 10mm more than the depth of the green roof build up.

That sounds a bit like gobbledegook doesn’t it.

construction of a timber green roof edging

A rough-hewn timber edging for a pitched sedum green roof. 
This type of construction will only really work with a sedum blanket green roof buildup. 
When you make your own, you can choose better quality timber and shape/colour it to suit the building.

So:  If you’re building a flat roof and using the Enviromat green roof buildup to “green” it.  The green roof buildup will be 48mm deep.  That 48mm needs to tuck under the edging.  So the upright part of the edging needs to be at least 58mm deep (there’s another bit to fix onto it yet)

For a pitched green roof using and Enviromat green roof kit, the upstand needs to be at least 38mm deep.

Finally, fix a length of timber at right angles to the upstand so that it makes a ledge that overhangs the green roof by 20-30mm.

This is a very simple edging that you can embellish however you want.  The important thing is to have that gap between the edging and the building so that excess rainwater can escape.

You may also like these related pages

Buy ready made green roof edging 

How to build a green roof – video footage of a sedum roof being applied to a garden shed

FREE green roof growing guide

Garden sheds with green credentials 

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