With a roof peak at 26', I'd opt for a chimney mount or eave mount. Home Depot sells a 10.5' galvanized top rail, intended for chain link fence construction, but it serves very well as a mast. I would not want an antenna subject to wood smoke, but a 10' mast on a chimney mount solves that issue to my satisfaction.
http://www.homedepot.com/p/t/1003225...2#.UUOAQzfxc4I I would expect a chimney mount kit and 10+ foot mast should net at least 7' clearance above the flue. And you get an installed height of more than 30' AGL
3StarInc offers many mounting hardware options...
http://www.3starinc.com/roof_mounts.html
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