CHIMNEY RELINING .pdf
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When a chimney is in need of relining, the rules are so extensive and the requirements are so
intense that there should be no question about whether you should hire someone with the
appropriate skills and knowledge to do the work. Not every mason with experience in brick or
block construction has the appropriate experience in completing a chimney relining according to
the codes of the National Fire Protection Association. However, there is one additional
consideration: if the job is not done correctly, it could void your fire insurance.
Get help. You’ll need it.
There was a time when chimneys were not lined. Much property was lost due to the lack of that
In 1904, the National Fire Prevention Association (NFPA) prepared its first codification on
chimneys and fireplaces. That codification has undergone many changes. The most recent
standard is NFPA 211, 2013.Here we will concentrate on Chapter 4 (General Requirements) and
Chapter 7 (Masonry Chimneys).
Naturally, any change in the lining of the chimney must be done according to current NFPA
standards in order for that property to be insurable.
First, from Chapter 4 (General Requirements) we get this: “Castable” or plastic refractories used
to line chimneys or connectors shall be the equivalent in resistance to heat and erosion by flue
gases to that of… fireclay brick.” Fireclay brick has a heat transfer thermal conductivity of 500
degrees Centigrade, 932 degrees Fahrenheit. It becomes more important, however, when the
lining supports are considered. According to NFPA 211, Chapter 4, “Lining made of castable or
plastic [ceramic] refractories shall be secured to the supporting walls by anchors made of
corrosion-resistant steel capable of supporting the refractory load at 1,500 degrees Fahrenheit,
816 degrees Centigrade.” Some definitions might help:
Thermal conductivity is "the quantity of heat transmitted through a unit thickness of a
material - in a direction normal to a surface of unit area - due to a unit temperature gradient
under steady state conditions," according to www.engineeringtoolbox.com.
Castable liners: to begin with, a castable liner exists to protect the chimney’s masonry
from corrosion from the products of combustion. It’s mixed like cement and fills the void
spaces around the flues. This liner would be perhaps the best choice among all the options for
your chimney. However, it may not be the easiest choice for relining one.
Refractory—its definition is “resistance to heat.”
It follows that since yours is not a new construction, you’ll be faced with a retrofit of your
existing chimney. Unless that chimney has fallen, you must now reline it to fit the standards as
closely as possible. Therefore, we will assume a standing structure placed on a code-matching
foundation. It’s small consolation to know that if the house burns down, the chimney will
continue to stand. The mason who works on your chimney relining must know:
The concrete or noncombustible material on which the chimney has been placed has a
fire resistance rating of not less than 3 hours.
That if it was built according to existing code, it does not require the building itself in
order to stand and the load is transferred to the ground, and
There may be limitations on corbelling of masonry chimneys, processes of widening the
chimney’s base. There are many requirements for corbels; only somebody familiar with the
NFPA Standard 211 should be selected to do the work.
The standard is extensive. There are requirements for flue sizes, proximity to roof structures,
pass-troughs for ceilings and floors. There are numerous standards for cleanout facilities,
including standards for doors—distances from floors and markings for the door.
The person who works on this chimney relining must know where the bottom of the flue must
be positioned. He must know how to “firestop” all spaces through which the chimney passes
with noncombustible material. He must know to use galvanized steel or noncombustible sheet
material where the chimney passes close to wood joists, beams, or headers.
There are other concerns. Included here are reinforcement for seismic and wind activity,
thimbles (pass-through fittings for chimneys) and smoke tests where the chimney is proved to be
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