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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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General: Green roof: commercial substrates, borders and seed or instant turf?

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1 to 21 of 21

  1.  
    • CommentAuthorShevek
    • CommentTimeFeb 18th 2015 edited
     
    Yay, so it's finally time to install our green roof, before flowering in April. We're going for an extensive roof (100-125 mm substrate) with a 80/20 wildflower grasses mix.

    1. I've allowed for a 300 mm border all the way around the perimeter, in my mind to minimise the risk of plants interfering with the building. But having had a look around at photos on the web hardly anyone does this, instead maybe just a drainage channel at the bottom of a sloping roof. What do you think, do away with the border? Keep it along bottom edge?

    2. Should we go for a commercial substrate or try making our own by crushing leftover bricks, concrete? Seems like a lot of work but delivery costs for substrates are quite high.

    3. The commercial green roof people I've talked to so far have warned me off seeding the roof with seeds and instead recommend roll-out turfs. They argue that it's notoriously difficult to get a wildflower green roof going by seeding alone (onto an extensive substrate). What do you think?
    • CommentAuthortony
    • CommentTimeFeb 18th 2015
     
    They want your money!!

    we only did aggeregate at the bottom

    I have done them, build fail safe, yours will rot out the soffit, joist ends etc when it fails, use a gutter outside the roof. Do not run the drain pipe from the main roof onto it -- no way!

    I used normal materials, drainage layer, water retention, geotextile, sub soil, sedum plugs, 20 years ago, no problems.
    • CommentAuthorMikeee5
    • CommentTimeFeb 19th 2015 edited
     
    Be nice to see some pics of the finished green roof in bloom. What did you use for your waterproofing membrane? Tonys points sound on the ball.
    • CommentAuthorShevek
    • CommentTimeFeb 22nd 2015 edited
     
    This it what it already looks like. Gutter is already built.

    Why not run the pipe from the main roof onto it? Would be nice to attenuate all rainwater and filter it a bit before reaching storage tanks (+ we haven't allowed for fixing to EWI anywhere else!)

    Wasn't going to use a drainage layer either. Just extensive substrate straight onto geotextile layer (pitch is 9 degrees), but might form a drainage channel in 20 mm aggregate to give the water from upper roof a more direct route.
    • CommentAuthortony
    • CommentTimeFeb 22nd 2015
     
    Look what happens when it leaks!

    Generally you can't change a roof from normal to freen roof, green roofs haf far more structure, usually 300c/c joists and 75mm joists that are deeper than normal, typically 50mm deeper, deck 28mm ply.

    Water (wet stuff) weighs a lot, so be careful not to collapse the roof!

    I would like to see a sluice/overflow to let water when the outlet clogs up with grott or ice.
    • CommentAuthorShevek
    • CommentTimeFeb 22nd 2015 edited
     
    The roof is designed for a green roof load of 150 kg/m2.

    You've just reminded me I wanted to put a sluice in and didn't! Guess we'll retrofit that when overflows first time.

    Why do think dropping the main roof onto the green roof is a bad idea?
    • CommentAuthortony
    • CommentTimeFeb 22nd 2015
     
    Oh good!

    Additional water is not good in itself, it will bring with it grott, not good either. It will tend to wash out precious nutrients.

    I would lay a gutter on the stones straight into the outlet.
  8.  
    Stick some bits of 'borrowed' sedum up there couple of years it'll be covered
    • CommentAuthorShevek
    • CommentTimeFeb 22nd 2015
     
    We want flowers though!
    • CommentAuthortony
    • CommentTimeFeb 22nd 2015
     
    Sedums flower!
    • CommentAuthorShevek
    • CommentTimeFeb 23rd 2015
     
    You know what I mean! Like a meadow innit.
  12.  
    its a roof not a meadow ! Sedums light , excellent water retention , drought tolerant
    :bigsmile:
  13.  
  14.  
    that was started a couple of years ago with some little bits found randomly ,
    • CommentAuthorShevek
    • CommentTimeFeb 28th 2017 edited
     
    Our green roof is designed to 150 kg/m2 but I don't know the exact calculation and I'm wondering if we'll get away with increasing the load a little.

    We have C4 170 x 47 mm flat roof joists at 400 mm centres, spanning 2500 mm. 18 mm OSB deck.

    What's the maximum load we'll get away with without causing any problems?
    • CommentAuthorHats
    • CommentTimeMar 1st 2017
     
    Remember to allow for snow loading if your in an area that can get snow... A freind built a BIG shed with a low pitch and the first big snow meant that he needed to rebuild his shed in the spring.... am sure its all accounted for in your design. I have been trying to establish a wild flower meadow on a hillside, its not as easy as just sprinkling some seeds around on cleared ground... My green roof is not on a house but a shed and only has 70mm turf that i cut locally, the first year it died right back and then last year the more drought tolerant native grasses and sedums started to establish well. We will see this summer.
    • CommentAuthortony
    • CommentTimeMar 1st 2017
     
    what summer?
    • CommentAuthorSimon Still
    • CommentTimeMar 2nd 2017 edited
     
    Have you not installed your green roof yet? Thead suggests you were doing it a year ago.

    After two summers living with our Sedum and comparing to our neighbour's 'wildflower' I really would advise sedum rather than wildflower.

    The first year our sedum pretty much flowered continuously (in waves of different colour) from installation in May through to October. We didn't feed after the winter and last Summer wasn't so great but we still got flowers for a couple of months and more sparsely from then on. The neighbouring 'wild flower' looks good for a couple of weeks in May but (unsurprisingly) looks like a load of dead grass through the rest of summer, briefly greens in autumn before dying back in Winter. It hasn't been fed or maintained which I'm sure isn't helping but I just don't think grasses are drought resistant enough for an extensive roof. Sedum looks good all year.
    • CommentAuthorCWatters
    • CommentTimeMar 2nd 2017
     
    If you turf it make sure you have a good water supply available. It's amazing how fast turf can dry out and shrink leaving gaps. Our outside tap would only supply two sprinklers which meant moving them around our lawn every hour or so to avoid patches drying out. Meant someone had to be home most of the time until it fixed itself down.
    • CommentAuthorcjard
    • CommentTimeMar 2nd 2017
     
    125mm substrate? If that were all water, it'd weigh 125kg/sqm - your design limit is only 20% above that?! If it's saturated soil + a heavy snow, you could get over that easily..
    • CommentAuthortony
    • CommentTimeMar 2nd 2017
     
    Poorest soil, and thin then sedum plugs and look after them for the first year

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