I’m considering one for our ongoing garage build. Be interested to hear of peoples experiences or links to must know facts & build advice.
Ta

What is your reason for doing so? An expensive roof….

Will it be grass? Most are planted otherwise.

They offer good temperature attenuation, but poor insulation value in the soil (you need extra insulation on an inhabited building).
They offer an increase in sound insulation (but only worth it if walls are also good sound insulation.
They slow run off onto the ground, but no more than fitting (a cheaper) method of attenuation such as reducing the area you have paved, a swale, pond or hidden attenuating soak away.
They look nice, and you can grow strawberries up there (yum)

Good for biding your drug den from satellite images and heat seaking missiles as well.

Not a grass roof, but a sedum roof. We chose it because the roof angle is very gently sloping (too shallow for tiles) and flat roofs are ugly!

It’s not worked out substantially more expensive than a flat roof. The materials underneath the planting are pretty basic, and seem well protected from the weather by the planting. We spent just under £200 on seedlings, and they have expanded 10-fold to cover the entire area in less than 18 months, even though it’s north facing.

It’s lovely to look at from the upstairs windows, especially when it’s flowering.

must know facts

Pfffft come to the wrong place then. My 2p worth, don’t do it on a flat roof give the roof a slight run.

done both grass and sedum on commercial scale both have good and bad points. any particular reason why your doing it?. personally i think there just another maintenance issue, the buildings/roofs we have done always look unkept/neglected mainly due to weeds cutting tidying, but thats on a commercial building where people think someone will weed/tidy that

Just toying with the idea as I need a garage roof and its one of a few options. I have an idealistic view of it being a pretty nature reserve over my head. Could well end up with Onduline.

Anything you can do to improve the biodiversity of where you live is a good thing, so something mixed rather than grass. Here is a good reference site for you:

http://livingroofs.org/

Do not burn off cuts of onduline 😳

Did one a few years ago on the cheap
drainage layer off ebay , egg box type
weed barrier from garden centre
growing medium of crushed brick from building site and compost .
Some sedum seed off the internet.
Cost about £200.00 all in for a 6m x 4m roof.
A bit of time then to let the seeds grow and bob’s your uncle.
Just make sure your roof can take the weight as it does get quite heavy when it starts to rain.
Sedum is the lightest I think as it needs very little growing medium.