I'm having a screened porch built on the back of my house, and the porch's gable roof will be centered on, and perpendicular to, my house's existing chimney. Problem is, the ridge of the new roof will have to meet the chimney less than a foot from the top of the chimney. What are my options for raising the height of the chimney? It is brick with ceramic insert (circa 1966). I'm hoping there's a solution cheaper than building up the entire chimney. Thanks.