Expert: Bart Ogden - 10/17/2008

Question
I have a large brick chimney that seems to have been built around the 3
outside walls of the original brick chimney. Inside the original chimney is a
clay liner. A gas fireplace has been fitted into the fireplace, and a metal liner
has been put inside the clay liner.

When they put the concrete cap on the top of the newer outer chimney, they
did not put metal flashing under it and around the liner. Instead they put
plastic under the cap! I mean REALLY! Well, of course the cap has long since
cracked and pieces of brick have been falling off in little sheets. It's called
"spalling" I have now learned. It has gotten really bad, and the chimney is
basically falling apart. The mortar on most of the chimney except at the top,
is holding well, but the bricks are flaking off.

I got up on the roof the other days--no mean feat after 3 knee surgeries!!-
and looked inside with my handyman. I was able to see inside because he
was easily able to dislodge an entire brick from just under the cap! We saw
the wood that holds the cap completely rotted, and that's when we saw the
old much smaller chimney inside and the plastic instead of flashing under
the cap.

One man wants to face the entire chimney w/stone and rebuild thse cap for
$11,700 which is out of the question. I have been doing some research.
There seem to be some alternatives all of which include replacing the
concrete cap and putting metal flashing under it and up around the old
chimney and liner and caulking the dickens out of it (I don't think we can
just seal it with Flexible Chimney Crown Sealer as there is not flashing or can
we, and then caulk the heck out of it?):  

can i do this one? least expensive: 1. chip off all the loose bricks, replace
entirely the ones which are really broken, repair mortar as needed. get
through the winter. as i can afford it, reface over these bricks with cement-
first I imagine we have to put some kind of metal screen attached to the
brick to hold the cement.

2. tear it all(the outside chimney only) down and rebuild with a wood frame
with cement or brick or stone ( I can't afford this really)  and a metal
flashing...
What is the least expensive solution and can it be done in stages?
Thank you.  

Answer
Hi Chai,

Depending on the severity of the damage, you may have to completely tear down the exposed masonry and rebuild it.

If you simply chip off the loose bricks and put mortar over them, it might last you the winter and you'll then have to do more extensive repair work next year.

If a crown is constructed properly and to BIA standards (see bia.org technical notes on chimney and crown construction) this should not require metal flashing at the crown area.

The bottom line is, this is going to be an expensive repair.  It's hard work and if you don't hire someone who knows what they're doing, you'll end up with another mess.

Frankly, the $11,700 sounds like a very valid price for what you've described.  Anything else is probably just going to be a patch.

I recommend you contact a local CSIA Certified Chimney Sweep to do some on-site diagnosis of your problem.

Sincerely,
A . Bart Ogden, President
Home Safe Hearth & Chimney, Inc.
Wichita, KS
Voice  316-265-9828
Fax  316-265-9890
www.HomeSafeKS.com

CSIA Certified Chimney Sweep #2653
CSIA Certified Dryer Exhaust Technician #10
NFI Certified Wood Specialist
NFI Certified Gas Specialist
NFI Certified Pellet Specialist
NFI Master Hearth Professional
NCSG Technical Advisory Council Member