Stone and Marble walls are fire resistant raving
wont stop me from burning everything else around you.
We are still in the process of thinking of what to do when it comes to putting it out, but I believe by the end of it each side will have at least 1 way to put fire out not counting powerful magic or natural powers like rain or snow.
a few things to remember, fires are near to impossible to spread during wintertime, rain inevitability drenched all wildfire and forest fires, 66% of the time fires wont be a problem. this will also add depth of gameplay towards the changing environment for example:
Your enemy has tons of boiling oil which will burn all of your troops to death if you try to assault that gate.
As you a line your armies just out of range of his stronghold it starts to rain.
You quickly rush the gate with battering rams and army as the rain starts to really come down. Your enemy dumps all of his oil on some of your men, some of them burn but the fires do not spread. The oil fire inevitably gets drenched with rain and allowed your battering rams to continue ramming the gate.
If you rush a gate during a hut summer day human oil pots will dump all their sticky black gold goodness on you and the oil fire would spread and burn longer making that gate unattackable for long periods of time.