Flat roof insulation/ drainage

[snodgrass]

Can anyone suggest the best way to insulate the flat roof on the extension to our bungalow? There may be a complication in that it currently drains to a water butt which has to be emptied periodically. Would this be the time to consider an alternative means of drainage, if any is possible?

[booksworth]

I've seen this done recently: don't expect it to be entirely DIY. What I saw was the entire ceiling removed, insulation slabs fitted between the joists, and a new ceiling installed.. You may need a plasterer to hide the joins between the sheets of plasterboard. -.-.- There is an alternative, which is insulation slab that can be fitted beneath the ceiling, but I don't know where that comes from. I will try to find out. -.-.-.-.-.- Going in from the top will mean destroying a (presumably) waterproof covering, and ripping up lots of boards, and still putting the ceiling at risk.