Flat roof repair

[WorstPigeon]

I'm currently in the process of buying a house. It's a two story terrace with a flat concrete roof. My surveyor says that while the roof is okay for now, it's likely to require replacement of its bitumen felt covering over the next number of years. Does anyone have a ballpark idea of how much this might end up costing? Access would likely have to be via scaffolding to the rear as there's no internal access to the roof. The roof itself is about 35sqm.

 

[Branz]

Fibreglass is a better replacement option and the last time I looked it was c 50 euro a sq meter, much better than felt and much safer to apply than some k....er with a blow lamp