Sedum Roof

hello all, I am thinking of trying to create a sedum carpet on our bit of flat roof. It is 10ft x 10ft, west facing and felted.
Is there some kind of membrane I should use, what kind of medium should I grow them in and how do I fix it to the roof? It should not trap water underneath as it would probably rot the felt.
Is it best to grow the whole thing on the ground first, or what?
All suggestions very much appreciated. Ta.

 

i think you could use some pond liner

 

Mine is covered with grit and the sedum grows in it like weeds...I raked it out a few weeks ago!
:D

 

I think the felt should be covered with gravel of some kind anyway, to reflect the sun. The sun does more damage to felt roofs than the wet will.
I'm sure someone can put me right if I'm wrong, but its usual to spread a layer of wet roofing type pitch and coat it with gravel or peashingle.
A little extra gravel wouldn't hurt and as Pal says the sedum would root into that.

 

Thanks for your ideas all. Paladin, did you bother to use pond liner or just cover the felt with grit? If I need not use pond liner it would be much simpler.
As the roof is on a slight slope I suppose I could use a batton or something to stop the grit washing off.

 

Hi Blackthorn
I've some experience with sedum roofs - Have just installed one in a clients garden and put one in a show garden earlier this year.
The easiest way is to line your roof with pondliner. Then construct a timber frame to fit the roof space (roofing battens are fine), and taking into account the depth of the growing medium & sedum matting. The fact that the roof has a slight slope is a good thing, & I see you have guttering already. Use a light weight growing medium to a depth of about 50mm max - I have used old potting compost 20 percent mixed with vermiculite 80 percent and old crushed bricks 80 percent & sandy loam 20 percent. You could use gravel, but it can get quite heavy, and you would need to be sure your roof was strong enough to bear the weight. Sedum matting is fairly cost effective to buy - you could try internet sources- & can be laid straight onto the growing medium. The alternative is to construct a frame which is actually supported by upright timbers sunk into the ground & has a metal grid base lined with punctured polythene.
Hope this helps
Bayleaf

 

Thank you for that Bayleaf, I have looked at one site that uses Enviromat Sedum Matting, but the cost is �£38.77 per sq metre, means that my 9 sq metres will cost �£348.98 + carriage - much more than I can afford. If poss I would like to do as much of it as possible myself, including the growing of the sedums. I have quite a selection growing in various places already.
I think I will try the pitch then grit method, put some sedum into it and just see what happens.
I will let you know the outcome, but it probably won't be until Spring t'ill I can start on it.

 

Blackthorn..I must add that my roof is concrete!
Built in 1938..not bomb proof,but near enough,so weight is not an issue.
I think some pitch and a scattering of shingle would be ok on yours as it's not that big a roof area.

 

I have some patches of sedum, the yellow one that grows anywhere, on an asbestos roof along with some houseleeks.
They are managing to survive with almost no soil, they just need something to anchor a few roots to, after that debris builds up naturally behind the plants and a slow growth process begins.
Bayleafs approach is a bit more professional. :D

 

Just trying to be sustainable .....
There's an article about building a sedum roof in the latest issue of Gardeners' World mag - although the depth of the sides is excessive to say the least for sedums. The depth suggested in the article is more able to support a larger range of plants such as grassess & annuals.
Blackthorn - you could try raising your own in seed trays, it will take a while from seed, but if you have cuttings/offshoots, that should speed up the process, slightly. Enviromat is pretty pricey, I have a local supplier - it may pay to ask at local nurseries and garden centres or even be cheekier & ring round a few local designers if you can't source a supplier via the usual places (yellow pages etc)
Pitch and grit - more harm than good - repairs a nightmare.
As regards the timber batten - I'd frame it all the way round (will help to keep liner & growing medium in place & will look better)
Whatever you do, I'm sure it'll look fab! its the way forward....

 

How do you mean, Bayleaf, repairs a nightmare?
It seems to be a bit of a strange felt roof to me Blackthorn. The felt around the sides has the green mineral surface but the main bit in the centre doesn't.
Is it felt? or is it some other material?

[ 10. September 2006, 04:41 PM: Message edited by: pete ]

 

Pete, it is a felt roof but has been coated with pitch or something in the middle - don't know why the edges were left bare.

 

The edges look normal to me, as to why the centre is like that looks a bit strange to me.
Do you think its been repaired at some stage.