Green turf roofs

[Andy Dingley]

There's a shed. I plan to use it as a smithy, but it currently has two problems: the interior headroom is too low and it's plug-ugly from the outside. The current roof is corrugated cement boards on almost zero pitch.

My plan is to lift the roof slightly from inside so as to fix the headroom. Then to turf it, so as to make it look less of a concrete block from the outside. Any advice on making a green roof?

There are various commercial membranes available, but this seems excessive for something where I can tolerate a little soak-through and the odd rootlet. Also I'm not sure if they'd be happy with keeping the corrugated cement. Would the cement carry the weight anyway?

Sedum seems a popular recommendation for the plants, rather than grass. Planting in 3/4" plugs a couple of inches apart.

All advice welcome

[The Medway Handyman]

Don't. Bad idea invented by tree huggers.

[Andy Dingley]

Well it _will_ look better from the upstairs windows, which is the main goal here.

What's your problem with green roofs? I'm dealing with a pretty crude smithy here. If it keeps rain off my head, I'm happy. Although there are many ways in which the whole idea could go wrong, I think I'm insulated from most of those by my sheer low standards for what I need to achieve. A few drips or rootlets really aren't going to be a problem for me, in the way that a landslide or a collapse would be.

[Anne Jackson]

Tree huggers are a relatively new arrival; sod roofs have been around for centuries. A friend of ours put a sod roof on his new house when he built it (he's a stonemason) circa 30 years ago.

[meow2222]

I've done exactly that. The main issue is weight. A cement fibre roof is not intended to hold a deep layer of soil plus possibly snow loading, so I went with a shallow 3-4" of soil. If not watered, this dries to a crisp in summer, killing everything. If automatically watered when dry, it works. Didnt use any membrane, and it was fine. As long as you've got some ventilation in there, no worry.

I'd forget about sedum, you can grow all sorts of things up there if its watered. Vegetables, flowers, various stuff. You're limited by:

- wide temp swings, since theres very little thermal mass compared to real ground

- very shallow rooting only

- nothing big & heavy

- low growing plants only, otherwise severe winds can rip them out

Although there are a lot of limits, there are also a lot of options.

Just be aware that since you're nearly maxing out on the weight capacity of the corrugate and supporting structure, its not the greatest idea to go walking about on the roof where there are no supports underneath. You may therefore want to put up a caution fragile roof notice to cover your rear. And you probably should check the supporting structure is ok to avoid exposure.

Habitable buildings raise more issues, but for an outbuilding this works fine.

NT

[RW]

Yebbut...........It's Jockland........

That sort of thing is normal in some parts innit

;-)

[The Natural Philosopher]

I think its a great idea actually, but it does require some thought.

[tony sayer]

In article , Anne Jackson scribeth thus

How's he cut the grass, or has he got a mountain goat that isn't scared of heights;?..

[mcbrien410]

If you are going to raise the roof angle slightly then why not put some extra joisting in at the same time to take the extra load.

400mm or 16 inch centres plus even some of then dwangs.

Regards Chris @ Aberdeen

[Andy Dingley]

By "joists" here we actually mean "dubious looking steel angle with a lot of rust on it".

I'm confident that I can support the cement board, the load question would be as to whether corrugated cement can support the soil load, and if corrugations themselves are a problem. Presumably they'd near double the soil weight required, just to fill them in and get a flat surface.

[Mary Fisher]

I suggest you also ask on uk.rec.gardening

Mary

[unopened]

The traditional membrane is several overlapping layers of sheets of birch bark (which keeps out the water). I think it was something like

5-10 sheets thick. Two layers of turf on top, the first layer upside down. Should last at least 30 years before needing renewal.

The Norwegian Folkemuseum in Oslo has lots of buildings with this type of roof - they may be able to point you to useful resources.

Cheers,

Sid

[Andy Dingley]

I was supposed to be camping nearby last weekend, and this was one of the things on the agenda. However the wind and rain put paid to that!

They do have a green roof tipsheet, but it's a chargeable download. I'll probably pick one up when I do get up there - this roof isn't going anywhere quickly.

I'm also less than impressed by the technical sophistication of much information from CAT - it's frequently on a par with Greenpeace: well- intentioned but incapable of appreciating any of the subtleties. As an example (see the other thread) they're completely clueless on grey water handling. CAT's description of this suggests that it needs chemical treatment, appreciable energy costs and long-term storage, whereas the contemporary systems are low-energy and focus more on reducing storage times to control risk. Grey water flush _is_ a practical option for me as retrofit, but composting isn't - CAT takes a simplistic "composting good, everything else bad" standpoint.

[The Medway Handyman]

If God had intended us to have grass roofs he wouldn't have invented roof tiles....

[Mary Fisher]

I'm disappointed in you! A bit of water put you off?

OK, a lot of water. But it's only water.

So am I.

- it's frequently on a par with Greenpeace: well-

I disagree with you there.

Hmm.

CAT isn't the ONLY 'authority'!

There are different kinds of compost toilets.

I'm not at all keen on using bath and other washing water waste, it takes a very little time to become smelly and it leaves 'tide marks'. Rainwater harvesting is far better in every way.

Mary

[Mary Fisher]

That's very interesting, thanks. 30 years will see us out :-)

Thanks for that too.

Mary

[meow2222]

they can support 6" of snow, so stick to a few inches and its fine.

If you draw a cross section on paper you''ll quickly see they dont.

NT

[Mary Fisher]

Andy, I'd very much like to hear the outcome of this. I have full confidence in your ability to do it well but if you did make mistakes it would be good to have the benefit of your experience.

While we were in Scotland at the weekend a huge old rose tree blew over, exposing Spouse's aeroplane shed, which is 70 years old and has had little maintenance on that side because it was impossible to get to it. Snow White could have slept securely in there for a century. The other side is hard up against a neighbour's boundary and difficult even for my Thin Man to access.

We've decided to mend it with a new one but it won't be an off the peg version, he'll want to build his own. And I know that he'd like to have a turf roof, he's been suggesting one for the garage for years.

So that's the reason I'd like to know of any pitfalls you might encounter, please. You can use my private address, as above.

TIA

Mary

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Anne Jackson saying something like:

"I wish I hadn't done that with that sodding roof."

[Tim Lamb]

In message , Mary Fisher writes

*Adnams* new bottle store at Southwold has one. Not actually grass, I believe.

I tried looking for some info but failed. Sorry.

regards