Re: [GBlist] low tech green roof?

[Speireag Alden <Joshua.M.Alden.91@alum.dartmouth.org>]

Sgrìobh David Bergman:

>I've asked this question on this forum before, but are any of the 
>green roof systems you mention suitable for residential, i.e. wood 
>joisted, flat roof structures? I'm still searching for a feasible, 
>affordable green roof for our 6-story condo tenement-style building.

     On my small house I used rafters at 16 inches on center, then 
5/8" plywood, then two layers of bituthene membrane, then some 
salvaged carpet (pile side down) to protect the bituthene, then a 
layer of bales, and then a layer of manure.

     The rafters are big; they are calculated to hold 50 pounds per 
square foot of static load (the earth and the roof structure) and 70 
pounds per square foot of snow load.  But they work fine.

     Manure on straw turned out not to compost very quickly.  Next 
time I'll put a rich layer of manure, soil and compost up there.

     One caution:  I have seldom heard good things said about truly 
flat roofs.  I'd pitch it by 1-in-12, at least, to prevent pooling 
water in local variations in the roof pitch.

     Also, I recommend putting the insulation between the soil layer 
and the waterproof membrane.  That way the waterproof membrane never 
goes through a freeze/thaw cycle, and the insulation provides an 
added layer of protection for the membrane (not necessary, but can't 
hurt).

-Speireag.
-- 
To face death, live.

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