Minecraft Fireplaces made of brick?

I keep running into problims on minecraft with fire... I built a town built a blacksmith made a fire pit for it out of brick and its fully around with brick netherrack on fire in it but yet it keeps burning the blacksmiths house thats wood that is 2 brick stones and a full halfstone block away why? And I built a log house in the woods this time I built a brick fire place and put a hole in the ground I have cobblestone all around it and a brick fire place over it and it still lights my house on fire why?? Plus why can't I use logs or wood for the fireplace? They just burn up I hate using netherrack