Blackened area around water heater vent

1977 house. The LP water heater vent transitioned to an oval vent to vent to the rooftop from basement. The construction materials in this area was blackened (rim/floor/sill/subflooring). Heat from pipe causing moisture? Any thoughts/insight? I know the pics aren’t the greatest, but that’s all I got.

Thanks in advance.

Need clearance from wood and they chopped up that joist.

Not sure if the flue caused the black or not. Anything else that might dump into that cavity? Get that copper off that nail and put in proper supports…galvanic reaction.


Looks like the nail is stopping the galvanic reaction in the picture though.:slight_smile:

The “oval vent” looks like a single wall furnace duct.

A piece of galvanized 3+1/4" X 10" is a standard piece of wall stack. Hope that does not vent to the attic or some other crazy location.

May be from old oil heater burning bad.