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
condition.

Since then, I have been doing tons of research and I cannot find anything --
no codes, no descriptions, etc. -- that would address this particular
situation.

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
masonry chimney?"

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:
http://tinypic.com/r/t8rtac/5
http://tinypic.com/r/9unmvb/5 .

On Apr 18, 3:10*pm, "TomR" wrote:
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
condition.

Since then, I have been doing tons of research and I cannot find anything --
no codes, no descriptions, etc. -- that would address this particular
situation.

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.

I'm not sure I understand the geometries here. I would think
a 8 x 8 flue is measured on the inside. In which case, I would
think a 7" round stainless steel liner would fit. I would think they
might want more space to make installation easier, allow for
difference along the way. But if the flue is aligned, straight,
not screwed up, I would think you could get a 7" liner in.




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
masonry chimney?"


That's one that you'll probably have to ask your local code
official about as it sounds like an uncommon situation. If
it has to pass inspection, I'd make sure the inspector agrees
it's OK. Has the company proposing this done it before?
The obvious question with part B pipe, part chimney is how
you correctly connect the two at the transition point. Not
only from a flue gas point of view, but also so that it's
something sturdy to hold the B pipe, keep water out,
rugged enough to last, etc. You don't want a shyster
joing them together with just some sheet metal that's
going to crap out in 5 years.

wrote:
On Apr 18, 3:10 pm, "TomR" wrote:
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 condition.

Since then, I have been doing tons of research and I cannot find
anything -- no codes, no descriptions, etc. -- that would address
this particular situation.

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.

I'm not sure I understand the geometries here. I would think
a 8 x 8 flue is measured on the inside. In which case, I would
think a 7" round stainless steel liner would fit. I would think they
might want more space to make installation easier, allow for
difference along the way. But if the flue is aligned, straight,
not screwed up, I would think you could get a 7" liner in.

Unfortunately, the 8 x 8 is the exterior size. The inside dimensions on
these are variously listed on different websites as being 6 1/2, 6 5/8, or 6
7/8 -- but none say 7 inches. All of the chimney people that I talked with
so far say that a 6-inch metal liner will fit inside and 8 x 8 clay flue but
a 7-inch metal liner will not.

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 masonry chimney?"

That's one that you'll probably have to ask your local code
official about as it sounds like an uncommon situation. If
it has to pass inspection, I'd make sure the inspector agrees
it's OK. Has the company proposing this done it before?

They claim that they have done this and it's no problem, but I am not
convinced about that and would really like to be able to find anywhere that
describes this type of setup and says whether it is okay.

wrote:
On Apr 18, 3:10 pm, "TomR" wrote:

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.

I'm not sure I understand the geometries here. I would think
a 8 x 8 flue is measured on the inside. In which case, I would
think a 7" round stainless steel liner would fit. I would think they
might want more space to make installation easier, allow for
difference along the way. But if the flue is aligned, straight,
not screwed up, I would think you could get a 7" liner in.

P.S. Here's one link I found about clay flue outside and inside dimensions:

http://www.koppclay.com/clay_flue_lining.html

TomR wrote:
. . . . . ,
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
..
Just an update in case anyone is interested:

I later found out that, with natural gas appliances (my steam heat boiler
and hot water heater), it is permissible to use a smaller liner than 7
inches inside the original chimney chase -- even if the connector pipe going
into the chimney now is 7 inches -- as long as the input BTU's of the
appliances going into the chimney, and the height of the chimney/vent etc.,
are calculated correctly using a standard chart regarding the code
requirements.

Here's one link with those requirements:
http://inspectapedia.com/chimneys/Chimney_Flue_Size.htm .

In my case, the total BTU's going into the chimney/vent are 224 thousand.
And, given all of the other height specifications etc., I can use a 6 inch
liner in the existing chimney -- which will easily fit inside the 8"x8" clay
flue that has an inside dimension of 6-5/8 inches across.

That means that I can have a 6 inch aluminum liner installed inside the
existing flue and a 6 inch double wall "Type B" (B-vent) coming out of the
top of the existing chimney (after the existing chimney is torn down to just
above the roof line).


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:
http://tinypic.com/r/t8rtac/5
http://tinypic.com/r/9unmvb/5 .

responding to http://www.homeownershub.com/mainten...le-693699-.htm
hoodzies wrote:
Did you end up getting this work done? I have a setup similar where I have
a masonry chimney in the house, with a metal direct vent chimney above the
roof line. I actually want to replace the smaller direct vent gas stove I
have with a b-vent stove (which I already own), but it's hard to find anyone
that will do the work, even though I am fairly certain it can be done, even
if I had to put class-A chimney pipe above the roof and run a 4 inch liner
through the masonry chimney up through the new metal chimney.
Anyway, just wondering how you made out?

-Mike
TomR wrote:


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
condition.

Since then, I have been doing tons of research and I cannot find
anything --
no codes, no descriptions, etc. -- that would address this particular
situation.

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
masonry chimney?"

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:
http://tinypic.com/r/t8rtac/5
http://tinypic.com/r/9unmvb/5 .








--

Mike