Chimney liners serve three functions. They offer protection to your home from heat transfer to hazardous combustibles. Liners also keep the masonry protected from any corrosive byproducts given off by combustion. Additionally, liners offer a flue that is the correct size to offer the optimal appliance efficiency. Oil or gas furnaces and modern wood stoves need a flue that is sized correctly in order to operate properly. Liners that have been sized incorrectly can cause excessive creosote to build up.
As briefly touched upon earlier, waterproofing is a good idea. Bricks are much like a sponge. As water touches a brick it begins to penetrate into the interior of it causing the brick to get weaker and ultimately crumble. In order to avoid any potential damage caused by water, it is a good idea to have a professional waterproof it. It is important to understand that waterproofing products available for your deck are not the same for your chimney. A chimney professional will have the proper product and the skills to apply it properly for long lasting effectiveness. In fact, one of the best ways to protect your chimney is to waterproof it.