Leaks that form around chimney fireplaces may be difficult to identify. A common problem is usually the chimney flashing. Chimney flashing is metal that is cut into the brick joints and protects the chimney. The chimney flashing may be old and needs to be resealed or replaced. If the chimney fireplace is made of brick the actual brick may be cracked and tuckpointing work is required to fill the cracks in the mortar. It is best to have a roofing professional look at the chimney to try to identify the source of the leak.