I want to lay decking and a half-height trellis surround on the flat
roof of my kitchen/bathroom extension to make a roof terrace.
Basically I'm laying 3x2 direct onto the felt roof in the direction of
drainage flow, and screwing the decking directly to them. I plan to make
it in four seperate sections, so the whole thing can be more easily
lifted for felt cleaning/replacing when necessary.
My question - decking is heavy stuff. I can work out the joist spacing
in the extension (450mm centres), but have no way of knowing how big the
joists are without destroying the ceiling. Does the fact that the joists
are spaced at 450 indicate enough strength to support the weight of my
Thanks for any advice..