"Christopher Norton" wrote in message
...
The design requirement for a man load on flat roof joists will mean
it
can carry almost as many growbags as you require.

Loading is almost certainly not a factor in this case. If you want
me to
check then get the size of the flat roof joist, with the longest
distance between supports and I`ll do a quick calc to prove the
loading
for you. 8-)


What if there are no joists ?
My flat roof is made by flat concrete panels.........
Jenny