On 28/07/2020 10:54, Theo wrote:
Andy Burns wrote:
Theo wrote:

some degree of sagging which causes ponding -
possibly due to movement of the underlying structure

Can you get any wedges/packers between the top of rafters and the
ply/osb/why?

Possibly by taking the ceiling below out, but then I'm not sure that making
good the ceiling is going to be much less work than redoing the roof.
(There may be asbestos fibres in the ceiling, just for added excitement)

Theo


Sounds like it has already leaked allowing the decking to weaken and
sag, hence the ponding. Complete re-decking it the solution.

Be aware that part L means it will need to be insulated and too
many roofing people will insist on adding insulation on top of the
decking and then putting the felt over the insulation. If your flat
roof is a 'cold roof' (most are) , this is s complete waste of time
since the ventilaton will still allow cold air to circulate underneath
the insulation.

If the roof is redecked then adding 'celotex' between the joists and cut
to fit snugly, and the joints taped with silver foil tape with an air
gap above it is the way to go.