Using structural steel or reinforced concrete one can create large buildings quickly. Portland cement gains strength rapidly. Gypsum plasters set almost instantly. Off-site manufacturing of entire bathrooms and kitchens which are craned into place is increasingly common. Click-together polymeric components even avoid Tadeusz, his nailbag and hammer.
However, lime mortars and lime plasters mean slow building - as does ashlar or cut stone. Lime mortars cure by CO2, and this can take months. When cathedrals were first built, the building season halted in the Autumn, before the first frosts. Recent work was covered in straw and thatched and left to cure for several months. There are no accelerants for hydraulic lime.
The damage to cracked but uncollapsed rib-vaults at Notre Dame will be infinitely harder to repair than the collapsed ones. Those flying buttresses are presently pushing the roofless walls inwards, and a temporary but substantial steel structure will be needed to stabilise the nave - wind loadings could still collapse the fragile structure.
Not to mention finding sufficient European Oak timbers. As an aside, a Nelson-era frigate took about 600 oak trees to build - and we had a fleet of 900 ships. Those oaks were planted in the 17th century by Pepys expressly for that future purpose. We no longer have a reserve of large structural oaks. For the stone, old quarries must be re-opened, masons recruited from all over Europe and the cathedral close will be alive with the clink of stone on bankers.
My own guess is twenty years. At least between fifteen and twenty-five. Something in that scale. Notre Dame will be covered with a vast temporary roof and be encumbered within by a massive steel structural frame for a generation. Macron is a fool and away with the fairies.
And now for the first of my EP election memes - I return to Twitter for such events with all the enthusiasm of a plumber clearing a blocked toilet.
