[iguy]

I believe exterior timber was banned in London after the fire of 1666, and in many other towns not so long after that. A brick skin just gives you much more time to stop a fire from spreading. Even when the exterior walls are load-bearing brick, a lot of internal structure may still be in wood.

[willyt]

That's not strictly true, the rules [0] on what fire tests a cladding material must conform to are quite complicated and depend on how close adjoining buildings are and whether there are any windows in them.

[0] http://www.gov.scot/Topics/Built-Environment/Building/Buildi...

[iguy]

Right, I'm sure the modern rules are very detailed. But at some rough level of walking around & looking at buildings, there's a step change right after the great fire.