Someone at work asked me why the church was burning since it was made of stone. I explained that it was a wood structure to which the stone was attached which also explains the flying buttresses.
Stone wasn't "attached" to the structure. Wood roof trusses supported the roof, and the flying buttresses--which made their first appearance at Notre Dame--supported the walls.
The trusses--which mostly burned today--were above the groin vaults you saw if you walked into the church and looked up. So I suppose one question now is whether to build another wooden roof, or use more modern--and more fireproof--materials.