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16-Mar-2015 4:20:17 PM
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I've noticed a number of engineers lurking on Chockstone... !
Hoping someone can help - planning to install a green roof on our new garage/ aka the-woody-storage -facility and need a structural engineer to check the building will be strong enough to withstand the added weight.
The proposed green roof will be aprox 30cm deep for low-lying natives, max 100kg/m required I'd say (TBC).
Any structural engineers on chockstone with an interest in green roofs? Or any recommendations?
Thanks :)
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16-Mar-2015 4:47:22 PM
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to get it through council you will need it designed and signed off to be structurally sound .Normal tin roof is 10kgm2 so quite a step up is required . The garden mass will vary with moisture so drainage will be critical
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16-Mar-2015 5:31:13 PM
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Nominally the density of topsoil is around 1.5-1.8 T/m3 depending on how consolidated it is.
If your putting in a 300mm layer of soil that's 450-550 kg/m2
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16-Mar-2015 8:41:37 PM
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One word- Biomass
converting carbon dioxide into 60m bluegums can add a 'bit' of weight above what the wet soil would add up to
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16-Mar-2015 8:44:45 PM
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On 16/03/2015 mike3091660 wrote:
>Nominally the density of topsoil is around 1.5-1.8 T/m3 depending on how
>consolidated it is.
>
>If your putting in a 300mm layer of soil that's 450-550 kg/m2
Those bags of soil you see at Bunnings are 30lt - once wet that'll be well over 30kgs.
How many of those bags can you fit on your roof?
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16-Mar-2015 9:05:44 PM
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Don't listen to the nay sayers, just go for it!
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16-Mar-2015 9:41:18 PM
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On 16/03/2015 Eduardo Slabofvic wrote:
>Don't listen to the nay sayers, just go for it!
Yeh. Ignore the rules and regs, do gooders and poli correctness police, just go for it.
Beef your roof beams up first tho.
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16-Mar-2015 11:23:17 PM
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As others have said, the existing structure is almost certainly too weak to hold the additional mass.
>The proposed green roof will be aprox 30cm deep for low-lying natives,
>max 100kg/m required I'd say (TBC).
30cm of earth!? Try ~450kg/m^2.. Your existing roof is probably good for 50kg/m^2 live load. Wind loads are likely of similar order of 50kg/m^2 but aren't considered to be combined with live loads.
So what you are talking about there is increasing the expected load by ~9X!!!
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17-Mar-2015 11:41:22 AM
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Thanks Guys. You're all correct - topsoil is very heavy, especially when saturated!
Apparently green roofs tend to use lightweight growing mediums e.g. vermiculite mixes, which bring down the weight . A landscape architect is advising on growing mediums, plants and resulting weight m/2 for a shallow green roof, as well as the layers required e.g. waterproofing, root protection barriers, drainage layers etc. Her brief phone advice was that for 30 mm depth additional weight would be around 100kg/m mark (TBC).
However, we'll need a structural engineer to calculate the weights based on the LA's advice, and work out what additional reinforcement the garage would need. We haven't built it yet, so hoping its easier to build strong enough rather than retrofitting. A bit unusual, so guess it would be best to hire an engineer with at least an interest in the area, if no direct experience. Was hoping some of the engineers on chokky might fit the bill or know someone... given we tend to enjoy the outdoors more than some!
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17-Mar-2015 11:58:10 AM
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On 17/03/2015 startedwithtrees wrote:
>Thanks Guys. You're all correct - topsoil is very heavy, especially when
>saturated!
>
>Apparently green roofs tend to use lightweight growing mediums e.g. vermiculite
>mixes, which bring down the weight . A landscape architect is advising
>on growing mediums, plants and resulting weight m/2 for a shallow green
>roof, as well as the layers required e.g. waterproofing, root protection
>barriers, drainage layers etc. Her brief phone advice was that for 30
>mm depth additional weight would be around 100kg/m mark (TBC).
>
>However, we'll need a structural engineer to calculate the weights based
>on the LA's advice, and work out what additional reinforcement the garage
>would need. We haven't built it yet, so hoping its easier to build strong
>enough rather than retrofitting. A bit unusual, so guess it would be best
>to hire an engineer with at least an interest in the area, if no direct
>experience. Was hoping some of the engineers on chokky might fit the bill
>or know someone... given we tend to enjoy the outdoors more than some!
First thing needed is the size of the garage ie length by width , the load to be carried is proportional to the span squared that is 4 m width gives say a load of 16 where as 6 m give a load of 36 is more than double
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17-Mar-2015 12:04:09 PM
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I may be able to give more specific advice. PM me for details. (I can do structural design, I cannot sign off on designs.)
Is the garage going to be timber structure? Steel?
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17-Mar-2015 12:14:23 PM
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I've got garden beds that are elevated off the ground which I filled with 1/3 compost, 1/3 coir, 1/6 vermiculite and 1/6 perlite. It's definitely much lighter than topsoil (maybe only 0.5 T/m^3 when dry), but as it's so much lighter, plants can't root themselves in as firmly, so if installing on a roof, you'd want to be wary of tall plants being torn right out by strong winds.
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17-Mar-2015 1:01:08 PM
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There is green roof at Melbourne Uni's campus at Burnley. Trying searching for info about that.
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19-Mar-2015 12:36:13 PM
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My Mrs works in sustainable urban something or other and said this website might be able to provide some good info.
http://www.growinggreenguide.org
Good luck and keep us posted on how it develops.
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19-Mar-2015 4:51:30 PM
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On 17/03/2015 BA wrote:
>There is green roof at Melbourne Uni's campus at Burnley. Trying searching
>for info about that.
Whaaa...eerrrrr...u mean like go ta google ...an type in ....green roof melbourne uni ...?
Aaawwwww .....fk me .... look at that ... BA ... it worked ...
http://voice.unimelb.edu.au/volume-9/number-3/gardens-sky
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20-Mar-2015 10:24:33 AM
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On 19/03/2015 Imaclawfan wrote:
>Whaaa...eerrrrr...u mean like go ta google ...an type in ....green roof
>melbourne uni ...?
>
>Aaawwwww .....fk me .... look at that ... BA ... it worked ...
Of course I meant it like that. Or maybe it was because I was too lazy to do it for you :-)
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