What to do with massive roof pooling issue

[gehngus]

I have been asked to sort this out and I'm thinking I should pass it on.
It's a concrete roof so it shouldn't be pooling like this. Maybe too many old layer of roofing on top of each other caused this? Lord knows.
it was leaking and I cleaned the lot off to redo the seams, but said the real issue is that water isnt leaving the roof and that seal won't last long. Water is 25mm deep before reaching an outlet.
As always this is a budget strapped business with tight pockets.
My sugestion is to either use tapered insulation to form a slope towards the outlets and epdm layer over top or to build a timber frame and board then epdm (or grp) to do the same?
Which would likley be the least expensive?
Self level has been mentioned but I cant see that working?
I'd appreciate any other suggestions.
Run away is already on the list.

Many thanks.

 

[gehngus]

Picture of roof in question

 

[accelerator]

I think you're thinking along the right lines. Any solution would need to change the roof from flat to slightly pitched to stop water pooling. It is however a big roof and a big job, so unless you specialise in this, perhaps best to hand-off to a specialist.

 

[gehngus]

I'm not sure anyone specialises in this concave water trap?
I specialise in building it right in the first place.
It's a decent size. Aprox 10x10 meter.
The issue here for me is any rain during work ends up below and it would be difficult finishing this on the same day. I have a decent team, but there are so many ifs and buts.

I would prefer to get it so water ran off to some degree and then do the actual work.

The owner doesn't want me to cut a channel or install a drain in the middle obviosly.

One thing is certain. Eventually all that water will find a way inside.