"David W.E. Roberts" wrote in message ...
"JK" wrote in message ...
[...]
The main issue you are likely to face is the structural strength needed to
support the soil and turf.

[...]

Just a quick environmentalist point. I'm all for as much greenery as
possible in built-up areas, but I couldn't in principle cheer for a
roof-top lawn in an area where the normal rainfall wasn't enough to
sustain it (rule of thumb guesstimate subject to correction from an
expert: anywhere east of the highland line?). We are hammering our
water-tables already, with bad consequences making themselves apparent
all over the country: I really don't think we can justify adding to
the demand just for an occasional bit of fun. So, if your project will
need tap-water, I have very sadly to vote against it; but if it will
be self-sustaining, I may even come and help with the hard work!

Mike.