Green roof?

[MissWing]

Hiya

We are planning to build a kitchen extension behind our semi. We are trying to decide between a flat roof and a pitched roof. A bit of googling has raised the possibility of having a green roof. Does anyone have any experience or views on these. Or a list of advantages and disadvantages? Estimated costs?

From what I can see they extend the life of the roof, although for me the appeal is that it would hide the expanse of flat roof.

We wouldn't be able to afford it straight away so the plan would be to build the extension with the roof and then get the 'green' part retrofitted. Any thing to consider here?

Thanks all
Miss Wing

Don't know much about them other than they are very insulating. I really like them but you have to be careful what you sow - there is a tendency for some of them just to become brown roofs after a few months unless you maintain them well...

we're toying with the idea too, being under the Heathrow footpath wondering whether it may help on days our runway gets used. also thought about constructing it ready to be seeded at a later date when we can afford the next stage.

any one else?

footpath , if only it were that small!

Thanks, legs, excellent thought, would be very sad if my green withered.

OK tmty, let's see if anyone else can offer any help! PS I heard in heathrow you can be paid to paint advertisements on your roof- possible source of income for your roof?

Take a look at www. Enviromat.co.uk/green-roof-design-guide there's some useful info about choosing plants etc that won't be too hard to look after

We're building a single storey flat roof extension this year and the planning department have insisted on a green roof - probably not a problem if its permitted development but we were surprised it came up! Haven't done it yet but will let you know how it goes!

They are cool, insulating, more attractive than bog standard roof and ecologically good.
You need to be careful that the structural design of the roof/Walls takes into account the weight of the soil/plants/water.
You also need to pick plants carefully to avoid a brown/dead roof.

Thanks for tips and positivity! (Keep it coming!)

got the builder coming Tuesday, so will ask him about additional costs for taking extra weight on new extension, and on new roof for existing kitchen. will report back.

We have a green roof. Advantages - it looks nice and it's environmentally friendly. It absorbs sound and is thermally effecient. Disadvantages- you have to weed and water it in Summer. Cost - think we paid c. £100 per square metre.
traditional roof would prob be 1/4 price but we love it. We went for sedum. Lovely when in flower.
You need to think about your aspect. It will get mossy if not enough sun.
Suggest you need an architect or green roof company for specialist advice. Most builders won't have a clue.

rowler - so sedum is not as minimal maintenance as its made out to be? expected a bit of weeding, and watering until established or in severe drought, but not much in the way of gardening

luckily our builder is a partner in a company with a structural engineer, so they will at least know about loads etc

No it doesn't need much at all really but weeds get everywhere so you do need to pull them out now and then. We water only when really hot but probably need to do it more as ours is a slightly pitched roof and not flat so water runs off.
When it comes to loads, you will need to know what type of green roof you are going for - some need a lot more support than others - our structural engineer didn't realise what type we were going for and totally over-engineered our roof so we have a massive steel supporting ours!

ours is as an alternative to having to retrofit proper insulation into a dodgy ceiling ....

we built a frame out of 6x1,
lined it with black horticultural membrane,
filled 4 inches with extratherm,
put on another layer of horticultural membrane
went to the hydroponics shop an eye opening experience and bought enough clay granules to cover the whole lot with a two inch thick layer

then we went to the garden centre and got rather carries away with sedums, sempervivums, and anything else in the highly drought tolerant alpines section
about 1/3 of it was covered but the granules look nice
its outside DDs bedroom window and in the summer is covered in flowers
its 4 years old now
some things die - in spring we 'll spend £10 buying new things to slot in among the granules with a couple of handfulls of extra compost
but because there is no soil, weeds do not set - think mediterranean roof type plants

my builder is currently installing a green roof at another project. unfortunately the expense means it's out of our budget. builder erred on the side of it being twice as expensive as pitched.

It will be extremely heavy. if you don't build an extra-strong roof it will collapse.

It is not actually insulating. An inch of polystyrene gives more insulation than a foot of soil. You will need both.

The soil will hold a lot of water so your waterproof membranes must be absolutely perfect.

ours is not heavy at all because it has no soil ....
6 inches of extratherm and one inch of clay granules with a bit of compost around the plants as they go in
AND
its on top of a standard flat roof : felted, tarred and sealed
so any flow through water runs down the tiles as the rest of the roof does

we know its not heavy because we need to jiggle it to let the roofer lean on it to repair the storm damage on the roof above

A family friend bought the parts and installed his own. He's super keen and shared the benefit of his research including where to source the various bits and pieces.

He was really happy with the Sedum mats he bought, he said there were no bare patches and lots of lovely mature plants in there:

www.sedumgreenroof.co.uk/