The mineral felt on this old flat roof dormer is being replaced not because it has reached the end of its life span but because the owner of the roof wants to install PV Photovoltaic panels over the roof, so before doing so he is going to install insulation into the roof and recover the roof makings sure the roof is in the best possible state of readiness before the installation of the Panels.
Flat roofing Hampstead by http://www.londonflatroofing.co.uk