[Womble]

Hi folks,

Has anybody built a living "green roof" before?

We need to build a new henhouse, and I'm seriously considering planting a meadow on top of it, rather than using boring old felt.

On the surface of it, it seems straightforward enough: build strong shed, put pond liner on roof, frame around the edge, leaving a drainage gap, cover in old towels / fleeces etc for water retention, add a layer of sand and soil, plant some things (not too sure what would be best for Scotland?), open beer.

What am I missing?   

[Penninehillbilly]

I seem to remember you need some cross sections, make a grid rather than a frame round the edge, or your growing medium all slides down to the bottom.

[YorkshireLass]

Yup. Have a wander around youtube, permaculture sites, and the Centre for Alternative Technology

[pharnorth]

We did our a few years back.  Very satisfying looking out on it rather than boring old flat roof stuff.

We used sedum to seed it as looks good, and didn't need mowing.  Don't know how well it does up your end of the world though. We used 30% by volume vermiculite (20kg sacks of insulation from the builders yard) with soil. This means you can get a reasonable depth while soil /sand would be too heavy and it takes on less rain, but releases it slower (feast/ famine can be a problem otherwise as you would need a fair amount of soil to hold the same amount of moisture but it would lose it quickly too)

Didn't do a mesh as ours only 3m by 4m. Also ours is flat flat a bit of a better run off would be ideal and you will do a better job of hiding the pond liner around the edges.

[Somewhere_by_the_river]

Thought this might be of some interest... Sedum and wildflower roof seems like a great idea! I wonder if OH would consider it for our garage/shed...?
http://www.sedumgreenroof.co.uk/sedum-mats.php

[Womble]

Thanks everybody!

The ready grown seed mats look great, but are also expensive, so I've cheated and bought some mixed sedum seeds, along with some flower seeds that are supposedly used in green roof systems. That way I can plant them in the propagator now, so they should be reasonably well grown by the time the roof is on the new henhouse. I'm hoping that if I plant a variety of seeds, they'll naturally select for the ones best in our location.

Likewise, the commercial systems seem to charge a lot for what's basically a plastic sheet with dimples in it to retain water. I'm not sure if that will be required for Scotland though, as sedums are naturally drought tolerant, and Scottish droughts rarely last more than a fortnight in any case.

If it is required, I reckon there must  be something out there that can be upcycled to do that job though? I plan to have a pent roof with only a slight slope on it, so losing the soil won't be a problem. (Maybe I should just eat more posh chocolates!!).



Any bright ideas?

[pharnorth]

Yes the proprietary stuff is silly money and not necessary for a small roof. Rather than dimple stuff we used a bit off old carpet on top of the pond liner.   Good excuse for upgrading the old dining room carpet to boot. It's a classic example of one of those jobs that if you do it by the book it costs £££££. If you improvise it is dirt cheap (pun intended) and just as effective.  We are in officially the driest part of the U.K. (Not far from Thetford) and it has survived many months with no rain at all and at least one winter out of five when it rained constantly.

[pharnorth]

Not the prettiest but inspired but the very expensive delapidated sheds at the Chelsea Flower Show. Haha

[Womble]

Drat. I don't think our carpets are in good enough condition to be used for that 

I think the problem is that when you start out (with anything really), you don't know where it's ok to improvise, and where you really need to spend the £££. We've got loads of old towels, so I can sew them together to make a big blanket, then cover the lot with a layer of locally sourced agricultural specification fleece sheep's wool. That ought to work, you'd think? 

[Fleecewife]

You could dot sempervivums all around amongst your sedum.  They come in all sorts of colours and forms, and push up alien-looking flower stems. If you buy a potful, you can divide up all the babies, root them and have a whole lot more plants for the price of one.     I would also add some trailing plants around the edges, such as thymus serpyllum, miniature aubretia, or even full sized aubretia, phlox douglasii, marjoram (the last 2 don't trail in fact  ) and anything else you can take as cuttings from your own or someone else's rock garden.  The thyme and marjoram will flower beautifully and be dripping with bumble bees in early summer.  None of those plants need a lot of water, but they do well here and we're WET      .  They are all shallow rooting and and spreading, and add more height to your roof and some dangly bits round the edges.  I like sedums (seda  ) but they are a bit uniform and unexciting.

[pharnorth]

Yes sounds good to me. The guide I followed suggested old blankets or a carpet.  For the most part it is not too exposed here and we did the job in May as ideally you want the roots to be knitting it all together before you get any really strong wind. I went round the loop on the risk on improvisation several times but concluded I was risking my time mainly and the expensive items were the sedum seeds and Vermiculite both of which I could salvage in a disaster. I'm pretty smug that 5 years on it is all still up there and apart from a couple of weeds each year zero maintenance

Love [member=4333]Fleecewife[/member] ideas on thyme and marjoram might through some seeds up there in the spring but do t agree the sedum is uniform and I exciting, it throws some glorious unexpected flower shoots in the spring which stand out in a roof, in the garden they are too small to appreciate.