I’m making a canoe rack. my original plan was to put a sloping onduline roof on it, but I’m now wondering if I could put a flatter green roof on it. The uprights are 100mm fence posts and the rails are 100x47mm C16. the long span is 4.8m and i’d like the roof to overhang a bit at each end as the sea kayak is 5.2m

Is it going to be feasible?

Yep, do it.
Drainage is the big issue, keep the weight down.
I’ve had a turf roof chicken shed not too different to yours.
My bike shed is a 8ft square brick built lean-to attached to my house, that was trickier as it had to be properly water tight. 7″ joists. I cheated and built a proper flat roof (slight slope, but less than 10° is called flat apparently) so I knew it was weather tight and met building regs and stuff and then just put a massive box of plants on it, seedum mosses of various kinds. It’s great, looks lovely, bees like it, almost no maintenance in five years (no need to mow) in the insulation properties are great.
Anyway, don’t overthink yours, just account for the weight and go for it.

Strawberry roof for the win.

How do i account for the weight over a 4.8m span, cant have a centre support as I want the boats to come out of the side. And drainage, hadn’t even considered that!
Anyone recommend a source of information?
I like the idea of a strawberry roof but I’m sure the cats would piddle on them.

Watching….. I have a half height bike store lean too planned that is to be built soon and I’d like to go green roof/strawberry roof just to make it less in your face

I like the idea of a strawberry roof but I’m sure the cats would piddle on them.

Stick a bit of mint in there with them, should put them off a bit. Birds will still have them, though.

As far as weight goes, sedums will grow on a light scattering of dirt on a bit of old carpet. You would probably need some additional strength in the structure, looking at your pic, but as long as the depth of material is small, and there is a way to help it drain easily (think about the pitch of your roof), you should be OK, it’s a small area.

Presumably you’re putting a slatted structure to support the kayaks? Make that beefy, maybe some extra thickness in the top of the frame, a vertical brace at the back and diagonal at the front?

We’ve got a sedum roof and soil is very thin. I also cut it with perlite to make it even lighter. The sedum is thriving

I’m considering this for our shed. A few how tos on the internet. The garden ninja explains how to do it fairly simply.

I would guess an OSB roof with well supported edges should be OK for the weight. The ninja seems to have just retrofitted a standard shed.

https://www.gardenninja.co.uk/green-roof-shed-installation/

Love the idea of a strawberry and mint roof.

I have the luxury of being able to build what is needed with few design constraints.

What sort of soil depth we talking about for that…..and as for drainage I had planned to bring the roof gutter down into a perforated pipe running along to top end of the roof to run onto the green roof…..is that a bad idea ?

We have a green reef over our bike shed, it is superb all year round. It is a timber sarking roof at about 10 degrees, maybe less. On the sarking is a waterproof tarp, on the tarp are old towels to protect the tarp from sharp stones and hold some moisture, a permeable membrane to stop washing out then a couple of inch max layer of sandy subsoil, perlite and stones. Plants are mostly sedum, herbs and fine grasses. Oh and a couple of self seeding rowan trees in a bonsai style. Despite being dryish and thin, it would be too heavy on your long spans so they will need some extra support. Could you put the bracing in as a triangle with the apex in the middle? That would maybe let the kayak pass through the gap still. Alternatively cantilever out from the rear of the rack like a large shelf bracket. That should leave space for the boat still.

The plants are all scavenged from gutters and waste ground but you can buy sedum in mats on the internet cheap enough, then break it up into smaller pieces. Now and again I pick out the boring grass that has self seeded. We never water it, and I think from experience if the plants need regular water they are probably the wrong type – If they can’t hack it then get something that likes it up there. I have never done this but I always fancied getting some wild flower seed mix and trying that – it should also thrive on crappy thin soil

I thought the span would be the fly in the ointment!
I need it to hold a canadian, a sea kayak and 2 river boats so bracing would really get in the way. I suppose my choice is between ideal storage and ideal roof 🙁

Ah I see, yes that would take up to much space in that case. I have a single sea boat that is quite slim so thought it might work. What about an extended post at the rear in the middle, you could maybe cantilever down off it to the roof? Or a single removable post at the front – take it out when the boats come out then replace it?

Our wood shed is slate roofed but I let an ivy and honesuckle grow over it, the honeysuckle grew very quickly and looks nice – great for bees too. Or maybe have two smaller green roofs around the uprights where the weight can be properly supported.

The span is fine, you just need to size the timbers appropriately. Probably somewhere around 200mm, but you can go a bit undersized as it’s not that critical.

How are planning on anchoring that bad boy down when its top heavy and loaded with voluminous lightweight objects that will catch the wind. Its a bit narrow to stay upright i reckon.

Bloody hell, I thought gravity would do that, it weighs a fair bit even without the roof.
I could tie it to the fence posts I spose?
It’ll be open all round so the wind will mostly go straight through?

I suspect a green roof would counter any wind uplift, dead weight will be circa 2kN/m2 against an uplift force of say 1.5 at worst.

Sizing the timbers will be important and installing a slope. If it’s flat and the timbers sag and it rains you might end up with a problem.

Typical build up would be ply deck, waterproof membrane, drainage layer about 25mm thick, growing medium say 40mm thick then a sedum mat.

Slope across the shortest distance and butt the above against a perforated angle. Either let it run off the the rear or use river cobbles in a drainage channel.

Green roofs are great 🙂

A lighter option is to use corrugated plastic as the drainage layer (and waterproofing) below the carpet, as long as you seal any screw holes properly. Water drains out of the sedum/soil/carpet layer and runs towards the gutter. You honestly don’t need that much growing medium below sedums if you use carpet.

We started out with corrugated on our extension roof, but it cracked when I walked on it, now sealed with rubber 🤣. Unless you’re planning to walk around on top of your boat store, it will be fine!

Well I have finally got round to building mine.

Its pretty much flat 6 ft across and 8 ft long.

The bed is 4 inches deep I’ve gone for an unconventional method of using what was lying about so

It’s 4*2 timbers with a ply deck with visqueen dpc plastic -then some 12mm rebar mesh I had lying about with fibreglass roof reinforcing mesh with minimal gravel -then weed suppressant. Then about 25mm compost/soil mix and sedums /mint /thyme /dill/corriander/basil

More importantly my cargo bike now has a dry home in an easy to get to location.

Picture’s worth a thousand words 🙂

I’ve ground to a halt with mine. I made it to fit our boats and ten minutes after I had it finished (roof excepted) the Mrs tells me she wants another open boat, so till we decide on that I don’t want to make any irreversible decisions on how and where the roof goes.

It sure is. But I’m not showing you orrible
Lot the garden that surrounds my green roof shed haha

But I’m not showing you orrible Lot the garden that surrounds my green roof shed haha

Honestly you really don’t want to see this “garden”

Ours has come together nicely over the last few months. Its
grown well and got a great diversity of species and is full of life now

Honestly you really don’t want to see this “garden”

Work in progress after the destruction of last year 😉 the sheds a marked improvement 😉

That looks awesome nickjb

Waiting on more compost Nd have changed my mind a bit. Due to the window height and the height of the child seat on the cargo bike the roof is considerably closer to the window than I’d have liked. So gonna move some of the flatter sedums from the front to the rear where the soil is going to be much thinner and then build up a bit at the front and try from some strawberry’s growing over – not too hopeful as it’s still a bit thin 4-6 inches soil recommended. I’ll probably have 2 inch tops.

Lotta bare looking space here but much of that is seeded with herbs.

Filled it up , got my strawbs I’m and they are growing well (were bare root no leaf when I got em) the mints going wild and the seeds are sprouting in various place

Dicht o paint and a tidy up inside.

I’ll wait the whole thing falling down since I ignored the trada span tables to a point as I’d not have got the bike in with a roof 6 inch timber based roof between the window and the ground ….and I’d rather put the shed up ever 5 years than have a shed not fit for purpose.- that said the roof timbers almost doubled up rather than 400 centres.

I opened this thread thinking it was going to be about the conservatory roof conversion company. Is disappoint.