I decided to start a new thread for this question. I had originally posted
questions about this chimney on 4/7/2012 using the subject heading
"Chimney - is repair possible?".
Here is the specific question that I have now:
Is it possible to just add a metal "B-vent" chimney directly on top of an
existing masonry chimney -- without the masonry chimney below being changed
or any metal liner being placed in the masonry chimney?
The reason that I am asking is that one of the many chimney companies and
masons that I had look at the chimney in question submitted an estimate that
included tearing the existing chimney down to the roof line, then adding a
triple wall stainless steel B-vent on top of the existing chimney from the
roof line up. According to them, the B-vent would go directly on top of the
existing 8"x8" clay flue with an adapter, and no new liner would be placed
in the existing chimney. This, of course, would be assuming that the
existing chimney and clay flue from the roof line down is all in good
Since then, I have been doing tons of research and I cannot find anything --
no codes, no descriptions, etc. -- that would address this particular
And, yes, it would make sense to at least add a liner to the existing
chimney if possible, but an issue has come up regarding that. The issue is
that going into the chimney is an existing 7-inch metal flue from the
gas-fired steam radiator heating unit and a 3-inch metal flue from the
gas-fired hot water heater. Apparently, since a 7-inch metal flue is
already going into the 8"x8" clay chimney flue, the minimum new metal
chimney liner size would have to be at least 7 inches. But, a 7-inch liner
will not fit into an 8"x8" clay flue. So, a new metal liner or B-vent
cannot be placed inside the existing masonry chimney without removing the
existing 8"x8" clay flue all the way down.
So, again, my question is, "Is it possible to just add a metal "B-vent"
chimney directly on top of an existing masonry chimney -- without the
masonry chimney below being changed or any metal liner being placed in the
P.S. For those who may not have seen my earlier thread about this chimney,
it is actually two chimneys in one:
This is a side-by-side twin home, so this is actually two chimneys instead
of one -- one for each house. The height of the chimney is about 10 feet up
from the roof line.
Here are two photos: