I need to repair my chimney above the roof line it's spalling and I also have found out that I need a chimney liner (I am missing tiles in the flue) I have had 2 estimates and one is double the cost of the other. My question is this - My chimney is 7 in across at the top and then there are some bricks sticking out in the middle that makes it 5 inches across. One repair man wants to put in a 5 in alum liner and the other wants to break out the bricks that are sticking out and put in a 7in liner. Does the size of the opening matter - does it need to be 7 in rather than 5? My chimney vents my furnace and hot water heater - no fire place. Please help! I need to do this ASAP.