Harry Bloomfield wrote:

Ken57 explained :

From inside, the roof seems to be made up of concrete beams arranged
like floorboards, with joins in places that make me wonder what
they're attached to.

From on top, it looks like crumbly concrete covered in various layers
of patching and gunge, (some of which I've just peeled off as it was
detaching itself), with several breaks in the level.


That looks very like concrete poroured in situ, which was supported by
floorboards whilst it was allowed to cure. The mess on top looks as if
it was once covered in pitch to provide waterproofing to the concrete,
later patched with the grey material.

Mmm. It may well be in which case its probbaly got steel reinforcing in
the lower part of it.

I suppose you could sort of lay down timber on props, with maybe a
pklsatic sheet over it, then lay a shallow layer of concrete, then put
dwon renforcing mesh, and then pourt a deep mix - probabably 6 inches or
so - to form the roof.

Seems bvery expensive though. These days you use bolck and beam I would
think.

The top surface will have be totally broken up by frost shattering if
teh waer oproofing has failed.

..





If the concrete looks serviceable, then just get a flat roofing
specialist to take a look at it.


I have another suggestion.
Lay a DPM and some poly sheet ob it and add another few inches of
screed, to get a bit of insulation, then cover the lot with tarred felt
stuff.



Or just screed it to a decent slope and put down tarred felt anyway.