Grass / living roof

[sarah barrows]

Hi, I am about to have an extension onto the side of my house with a flat roof – it’s about 30 square meters.

 

The current plan is for a zinc roof, however we are thinking about the possibility of a grass/living roof.

 

I was wondering what the pros and cons are for doing this?

Is it relatively simple to do?

Is it that difficult to maintain or is it just some decent effort that is needed?

Does it cost a lot more than a zinc roof?

And is this something a traditional roofer will do or is this a specialist trade?

 

Of course I have googled all of these but I’m sure this site will have the real answers !!!

[Dudda]

 

It depends on the type of grass roof you want. You’ve three broad types. Lightweight which is about 1 or 2 inches of soil that contains sedum plants and mosses. This requires very little maintenance and isn’t suitable for regular access as the soil is so thin. The next is extensive green roofs which are  deeper (about 3 to 7 inches) which allows you to plant grass and flowers and you can walk out onto. This needs a little more maintenance but not much. Then you’ve intensive which is anything bigger. This allows you to have a real garden with paving areas, grassed areas, shrubs, etc. The maintenance is like a regular garden cutting the grass and trimming shrubs if needed.

 

The heavier the roof the more structure you need and the more expensive it gets. You’ll also need handrails and parapets for when people are using the roof. The lightweight sedum roofs are relatively cheap and can be on a timber frame structure. They come with their own build up of layers and are relatively easy. The key point is it’s all installed correctly as like any roof finding a leak later is difficult.

 

Presuming you don’t need access and the lightweight is OK for you then it should be about the same price or not far off. They don’t need handrails as they don’t have regular access. The heavier grass roofs get very expensive. I’m not sure I’d trust the regular roofer down the road with a zinc roof. Slates sure but not zinc. The same is for a green roof but the layers and build up of a green roof are now relatively easy to lay and install. Environmentally and aesthetically the green roof I think is better and what I’d go with. If you’ve high bedroom windows that look out over a flat roof it’s nicer to look out over a grass roof than slates or zinc.

[Mr Punter]

Unless there is a planning requirement I would not bother.  it will be expensive to achieve and perhaps more difficult to insure.  A lot to strip back if there is a defect.  I would be concerned about fire in this weather too.

[ToughButterCup]

On 20/07/2018 at 09:30, sarah barrows said:

[...]

I was wondering what the pros and cons are for doing this?

Is it relatively simple to do?

[...]

 

We are just about to 'fit' ours. @Dudda's advice is exactly in line with what we have found out (but took years to do so  ? )

 

On 20/07/2018 at 11:10, Dudda said:

[...]

The lightweight sedum roofs are relatively cheap and can be on a timber frame structure. They come with their own build up of layers and are relatively easy. The key point is it’s all installed correctly as like any roof finding a leak later is difficult.

 

Presuming you don’t need access and the lightweight is OK for you then it should be about the same price or not far off.

[...]

 

Our flat roof build up is 'normal' : but you can bet your life I will be all over the nitty gritty detail. Not sure yet whether to have a GRP or EPDM top surface: there are horror stories and hymns of praise in equal measure for each .

 

So, that makes me almost certain it's all about attention to detail. What's new?

[mvincentd]

When my first quote came in at £52k for vcl, insulation, membrane, trim...I spent 3 months procuring a more rational quote elsewhere for £32k.....for exactly the same product.  In between I got quotes for numerous alternative solutions...none of them bettered the £32k i'm paying for my preferred option.   I had a reason for distinctly preferring one particular solution but i'd say if your project doesn't have any specific foibles/requirements just go with whatever fully guaranteed system is being offered by a roof co' that you gel with.  Every horror story about one system can be matched with stories about another.  By 'fully guaranteed system' I mean that a roofer will use his preferred product and be 'ticketed' to install it, and the product will have a specification written (by the producer) for its installation onto your project...and they'll inspect the work your roofer does with their product on your project before issuing the guarantee. Note that if you then plan to do the green roof bit yourself there may be expectations regarding what your green layers are, in order to maintain the guarantee.

[sarah barrows]

12 hours ago, mvincentd said:

 

hi thanks to you all for this very helpful information. this has definitely given me some food for thought and will assist me in my decision making process, although I havent decided yet !!

 

If I go for the green roof I will go for the simple, thin layer option and if I go for zinc then I will definitely go for a proprietary system. 

 

again, thanks so much for the replies - much appreciated. 

Edited July 23, 2018 by sarah barrows

[ToughButterCup]

1 minute ago, sarah barrows said:

[...]

although I havent decided yet !!

 

So far, I have been very grateful that I either delayed, or was forced to delay many decisions. Bit like the chippy who said to me the other day;

Don't cut a piece of wood until you really have to.