Stain on Asphalt Shingle Roof

stevedunn

Our roof is only 11 years old, but we have a dark stain which widens out as it runs down the roof. The stain begins at the oil-fired furnace flue pipe penetration through the roof. The height of the flue is exactly 3' above the roof. The flue is 2' from the ridge line, and is 2 ' 6" above the ridge line. No other obstructions within 15'. The only cleaner I've found that reacts with the stain is "greased lightning", which produces a foamy brown crud when scrubbed on the shingles. CLR does not react (not rust?) Flue pipe is not boxed in but is insulated and is labeled as "metalbestos". The inside of the flue pipe has a hard, crystalline black deposit, hard to scrape off, but appears to be ordinary soot. Anyone solve a problem like this? Should I raise the flue pipe up? Anyone regularly clean their oil furnace flue pipe? Any ideas on cleaning or do I need to replace the roof? Thanks.

AaronB

Try some soap.

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stevedunn

Thanks. Assuming the soap works to remove the stain, does anyone have an idea about how to prevent the stain from re-forming? I have been advised to try raising the flue pipe up about two additional feet to avoid what may be a downdraft laying down the (soot)? The heaviest stain does form on the down-side of the prevailing wind in our area. We are in northern New York as far as climate. We have no other stained areas on the roof.