I know what you're gonna say.... when in doubt get it inspected by a proffesional. I've already scheduled my chimney sweep to inspect it next Tuesday (its Thursday today). I just thought I'd get some feedback from the cumulative knowledge & experience of my fellow Hearth.com members. Following is the sum of it: It's my 3rd winter new to woodburning and in my own house. My woodburning stove is an Altlanta Stoveworks Huntsman (circa 1979) with about a 25 ft new fancy stainless stovepipe with the top installed by my chimney sweep at the beginning of my 3 winters here. The stove, pipe, chimney, placement, & fire safety precautions are all up tight & alright. BUT... I noticed today a brown stain I never saw before on the house side of my chimneys exterior siding (it's T-11 siding). I do not know why this stain is suddenly here after 3 seasons of my standard burning behavior. AHHHH, but alas...there was that day I came home from work to find the stove temping DOWN at 600 degrees ! My 15yr old had been tending the fire. My younger 12 yr old son called me at work afraid that the stove was too hot. I gave the expected phone freak-out & follow-up at home hollering to my 15 yr old.....but even after all that - I made no specific effort to inspect in depth beyond checking for obvious exterior signs of fire which I saw none. SOOO I dont know when this stain appeared & if this is the reason and if its a slow response to that incident or WHAT ? So my question more specifically is: Does anyone know about chimneys made of T-11 siding surrounding stainless steel stovepipes and how well do they work together ? Is the T-11 siding prone to brown staining under any circumstances ? Could it be simply a minor issue causing a cosmetic stain or is it an indication of internal damage indicative of these two materials used in combination? The Huntsman stove has a large firebox and I dont know how high my kid got it up to !