DIY Green Roofs

[BEN GERSTEN]

I would be keen to hear from anyone who has built their own green roof, most of the companies providing them do not advise DIY.

I would particularly like to here from anyone who has had one installed for a while.

I have been reeding lots of negative things about the environmental impacts of green roofs.

[Chris Herring]

Ben
I would be very interested to hear more about negative environmental impacts of these.  I know little about the subject and am intrigued.  I had assumed that apart from issues of increased resources (heavier joists etc) and impact of plastic membranes, these roofs were generally either  good or pretty neutral in impact.

[Andy Simmonds]

Ben
Go to the English Nature web site an ddownload report # 498: Green Roofs.... At the end of the report is a list of lots of projects that have green roofs installed over many years. Some of them are home made - including several of our own projects. Depends where you are in the country - you could visit some from the list.

[Nick Grant]

I've done 2 DIY green roofs on our dwellings plus a couple of sheds but it's too early to report on long term durability.

As an Ecominimalist I'm appologetic about our roofs which are an eco-cliche and I am sceptical about them being particularly green but I also don't see them as particularly unecological. Any building component that doesnt fail and trash the building gets ecopoints in my book!

What I have learnt practically, is that, not surprisingly, penetrations are the achiles heal for DIY. Also flat is easier than pitched.

We have used Hypalon (sp?), Butyl (flat wkshop roof, no penetrations) and Monarflex PE. All were factory welded to form a single sheet. For our house we used the PE and did the penetrations (Isokern chimney, 2 x Vellux, 2 x vents and 2 x downpipes) using monobond tape (like flashband).

It's OK but I am not 100% happy with our joins as the tape softens when hot so can creep if not weighed down.

Hot air welding would be better but needs proper kit and skill and Monarflex said they would use tape if they did it. I tried to get a local firm to do the welding but could only find people offering whole system with guarantee - peace of mind we didn't think we could afford at the time but might seem a bargain in hindsight!!!

I am enthusiastic about flat roofs with a dusting of pea gravel and compost planted with scattered clumps of sedum. Not too much weight, easy to do and look fine with just 5 clumps of plants whilst they get established - very Zen with the gravel backdrop but not up to heavy traffic unless you sandwich with plenty of geotextile.

Brian Richardson (Self Build Book, Segal Trust, AECB) used Butyl many years ago for his house and I think it was mostly OK but he did notice wood tar from chimney disolving the butyl and also wasps had made a hole in it.

Generally with proper detailing a green roof should last for ever as the liner is protected from sun and temperature extremes.

Robust roofing to cover our lovely thick eco insulation is a subject in itself and worthy of some serious consideration.

[Steve Smith]

Could anyone point me in the direction of some literature describing the DIY construction of a sedum roof. I am roofing a 4m2 shed and would like to install a green roof.

Thanks

Steve Smith

[David OLIVIER]

One of the original valid arguments for "green roofs" was that flat roofs then last much longer than other flat roofs - normally the waterproofing is broken down by UV within a few decades. Another way to prolong the life of flat roofs is to use the inverted type. They only need a single membrane. That is protected by the insulation, which in turn is protected by the ballast or paving slabs (these could probably be replaced by soil if it was advantageous).

Yes sloping green roofs can be rather an eco-cliche. The advantages of covering a pitched roof by vegetation aren't as clear-cut as they are for a flat roof. They're somewhat trickier to design and build than a flat turf roof and I understand the embodied energy is distinctly higher than say a slate roof of the same pitch. This is due to it needing more robust membranes, a more robust structure, etc.

D.

[Geoff Stow]

Nothing gets people talking like a Grass roof.

On the do it yourself level. Obviously you have to make sure the structure is strong enough to take the weight. You will need a smooth deck to lay the waterproof membrane on. This is usually covered with a thin protective fleece, then the waterproof membrane  (avoid PVC).

The membrane is covered with a protective layer, for small projects I have seen old carpet, which is free, work very well.

The difficulty I have had is retaining the growing medium in place while the plants get established. The steeper the roof the bigger the problem. I have found that if it is a problem you can just lay turfs on to of each other. unless you live in a very wet area the grass will die off but you can plant sedums in the turf. they do spread well.

If the roof is flat you will find that it will soon establish its own ecosystem.

Sorting out drainage is more difficult but there are plenty of flat roof outlets available from big plumbers merchants.

I think you can go round in circles on the environmental credentials of green roofs. Yes you do need to make the structure stronger and the liner has a huge amount of embodied energy. But they can more than replace the growing area removed by the building. Increasing the production of pollens etc. They do greatly slow down the run off of rain water which acts as part of flood prevention and it does apparently cool the area around the house in summer. And hey they can look great.

Have fun.

[Nigel Bishton]

I have constructed two buildings with green roofs, both pitched.  One I live in has been in place for 11 years without fault. The other is a large shed which has been up for a couple of years, again without any issues.

I have done these myself due to the fact that contractors charge a ridiculous amount to do the work.

I would advise that you have a modest pitch and use a lightweight growing medium such as leca and peat free compost. Sedum plugs will happily grow in this.

I used the system sold by safeguard chemicals.
See http://www.safeguardwaterproofing.co.uk/applications/green_roofs.php

It is easy to use for a competent diyer.


The attractions of a green roof are:

1. Visually less impact especially in a rural situation.
2. Water Retention reduces water run off.
3. Increases biodiversity.
4. Increases thermal mass and reduces summer overheating.



I dont believe they are suitable for all situations and I do not understand why some people are so negative about them.

I also dont buy the embodied energy arguement unless you choose to ignore the fuel involved in mining and transporting slate (??from china) and the environmental impact of mining.

[Brian Waite]

look at Patrick Blancs website - a bit poncy but very exciting. Then look at www.strawbalehouse.co.uk - not relevant but it is my own! Brian

[Alex Hunt]

I have to agree with Nigel,
the safeguard system is pretty easy, straightforward and seems to be doing the trick on a 16m2 garage roof i installed in the summer (even after all the snow we had this winter!).

we used Coir blocks rather than soil (coir made from the insides of coconut husks) - lightweight, easy to install and seems to be perfectly good for the sedum matting we used.

Its still early days - but the roof looks great - loads of wildlife seems to be attracted to it.

I have photos if you're interested.

[Julia Bennett]

Ben
After all that lovely discussion, what did you do in the end?

I'm planning to build an open-sided shed for clothes drying during work days / all weather kids play, etc., with a sedum roof in the next few months and would love to hear how you got on.

Already I've twigged that I need to build in some sockets now into the membrane to receive future tilted frames for PV panels, or come up with a penetration-free fixing solution.... (cogs stirring ).
Joolz

[Andy Simmonds]

Julia - make it a wind tunnel.

[Dr Jonathan Rae]

People reading this thread might be interested to know about a course running at Schumacher College this autumn. It's a five-day residential course that covers every aspect of green roof and wall installation - from design to which materials to use and where to source them.
Take a look here for more info.
http://www.schumachercollege.org.uk/courses/using-living-roofs-and-walls-a-macro-and-a-micro-perspective