flat roof and falls query

hi all.
hi doing a flat roof in a warm roof construction.the roof is a refurbishment less than 20 years old with all paperwork to say it passed the regs of that time.My question is,is putting firings in a requirement of building regs for a refurbishment,i understand its good practise but is it actually law.As i spoke to our local building regs bloke at council who says this is one of the things he would be looking for,my point being if the construction has been passed once by them they would according to him have required some kind of fall to have been built in at that stage as according to him no flat roof is really flat and should have fall built in.

Are you saying the roof was built dead level without any fall? In any case he's quite right, a 'flat roof' is never actually flat or shouldn't be and will certainly not pass building regs today and rightly so. It would be bad practice to do it completely flat. The absolute minimum fall is 1:80 but even then thats hardly any fall especially for a timber roof that can sag over time. Why it was passed 20 years ago is a mystery.

In technical terms, the only requirement for a roof is that it is waterproof.

So it would be possible to construct a completely flat roof, that drains by an outlet as it fills. You could even have a swimming pool up there if you like

But a traditional flat roof covering will age prematurely if it does not drain properly. Water ponds, and causes uneven expansion/contraction and stresses the covering - especially traditional bitumen or asphalt

So furrings are not a requirement of b/regs, but the roof structure and covering must be designed to deal with any retained water

thanks chaps,but the way the building inspecter was going on about firings did not make sense to me as he kept saying this is what he looks for and for any flat roof to pass inspection it needed a fall.so my reply being if that was the case how did you guys pass original roof.as all i am doing is refurbishment but at this point i could see the point of improving falls.but i could not see how he could fail if i did not wish to improve