FIRE Pathing

I recently designed a redstone entrance to a dungeon, that would start in my house's fireplace, drop down, and relight the fireplace. 

It was then that I discovered that fire can burn wood even if the fire is surrounded by stone and steel. Half my house burned down unfortunately. 

I think this mechanic should be changed and that fire cannot spread to wood that is blocked by stone/metal blocks. This is how it works irl, and would make for cooler fireplace designs.