Refractory mortar that begins to set on contact with air.
Al2O3 is an amphoteric oxide of aluminium,
with a high melting point. Extremely abrasive at 9 on the Mohs
scale. It is derived from Bauxite. Corundum is crystalline
As a general rule, the higher the percentage of aluminium oxide in
a refractory brick, the higher its temperature rating.
The side walls of the secondary combustion chamber over which flow
the gases as they leave the chamber and enter the side channels.
Fine grained plastic sedimentary clay rich in Kaolin Extracted in
cubes that became rounded during transport to the surface.
Relatively scarce, deposits are found in England and NE USA. First
used in modern times for making tobacco pipes in the mid 17th
Bottom Up Burn
Name used to describe the traditional fire laying technique in
which the paper and kindling are layed first followed by the
medium and then large wood. The fire is lit from bellow and burns
A mechanical device used to divert the flue gases from the heater
directly into the chimney. Usually located between the secondary
combustion chamber and the chimney, or between a manifold and
chimney when used to by-pass a bench. The principle function of a
bypass is to establish a draw before engaging a portion of
extended smoke path.
The castable refractory slab or slabs which close the top of the
Castable Refractory Concrete
Heat resistant concrete that can be pre cast to form modules to be
used in the construction of a refractory core.
High temperature woven ceramic fibre blanket, used as an expansion
and smoke gasket.
Cap, usually in concrete used to close the chimney top around the
tile, and to protect the masonry of the chimney top from weather.
The point at which the heaters smoke path is connected to its
Installed over the flue tile on the chimney top to prevent rain
falling directly into the flue.
Chimney Shut off Damper
A mechanical device ,located in the chimney, used to close the
smoke path after combustion. Also used to control the combustion
by restricting the smoke path.
Chimney top damper
A chimney cap that also acts as a shut off damper, closing the
smoke path on the chimney top. Usually operated by cable from
inside the dwelling.
Mortar used specifically in stove and oven building. Typical mix
is one fatty clay to 5 sand.
The efficiency of both primary and secondary combustion. Not the
efficiency of any one appliance. \
Type N Mortar
The mortar generally used for the laying of a heaters façade and
masonry chimney. 1 Portland Cement: 1 lime: 6 sand.
A course of masonry that is layed off plumb from the course below.
A way of closing a narrow opening by corbeling in from each side
until the two corbeled portions of wall meet and support each
A series of small fires lit immediately after the heater has been
completed. These fires, gradually increasing in size are intended
to dry the heater slowly, thus avoiding trapped water having a
mechanical action on the materials.
Upper chamber oven having its bake chamber as part of the smoke
path. Secondary combustion taking place within the bake chamber.
The name given to a masonry stove which is connected to its
chimney at the bottom, i.e. floor level.
Gasket usually, but not necessarily, of fireproof material, placed
between two materials with a different expansion coefficient. Or
two similar materials, with a different expansion rate against
A single wythe masonry skin, enclosing a refractory core providing
the heater's double skin. It can consist of any standard dense
Finnish Fire place
Finnish form for the Finnish Contra-Flow masonry heater.
Finnish style cookstove
Masonry cook stove
Masonry cook stove typical of those used in Finland and
Scandinavia. Achieving only partial secondary combustion, a
masonry cookstove is completely independent of a masonry heater.
Primary Combustion Chamber
Chamber in which the fire is layed, and in which primary
combustion takes place. Accessed by the fire box loading door.
Area of the core directly above the fire box where secondary
combustion takes place. Found in cores with an undefined throat
and upper chamber. Unlike the upper chamber the fire tube does not
rely upon compression and expansion of the gases to promote
Lining tile inserted into a section of masonry chimney to bake the
chimney double skinned.
Fine particles of ash that are drawn through the smoke path, often
accumulating on its horizontal surfaces.
A module that is not physically held in place by mortar or
masonry, is said to be free floating.
Suspended Crystalline Silica
Fine crystals of silica suspended in the atmosphere in the form
dust. Caused by the working of silica containing products. A
general and specific safety hazard for the Mason.
A raw refractory material, high in silica and alumina. Having a
relatively coarse particle range, grog is usually light and
Local name for the German version of the masonry heater. Built by
an Hafner or Ofensetzer.
The groundofen is distinguished by its lack of grate, and it
usualy being built directly onto the floor.
Barely visible cracks in masonry, no thicker than a human hair.
Hand Built Refractory Core
Custom built core
Site built refractory core. Usually built by a qualified
specialist entirely from refractory brick.
Heat exchange channels
The heat exchange channels that run down each side of the core,
separated from the core by a heat resistant gasket.
Heat set refractory mortar
Refractory mortar that sets only on contact with heat. Less common
that Air Set Mortar.
Portion of extended, horizontal, smoke path deviating from the
heater, before re-joining the chimney.
High Temperature Cement HTC
The pre mixed water or paste used to lay refractory brick. In
France the product referred to as Mortier Refractaire is not the
product referred to here and has no use in the construction of a
The name given by the Romans to their system of heating bath rooms
by running flue gasses through a series of masonry heat exchange
channels, usually in a floor. Though never or rarely achieving
secondary combustion these heating systems are considered to be
the first recorded examples of the deliberate use of thermal
retention within masonry mass. Evidence of their use can be found
throught the former Roman world. A-Z Index
Oven located in the upper chamber but being entirely closed to the
smoke path. Secondary combustion takes place below, above, behind,
and to the sides of the bake chamber.
An adaption of a contraflow stove where the gases descend one side
channel, and return up through the other side channel before
exiting at the top of the stove. As opposed to the gases
descending both side channels and exiting at the bottom.
Local name for the Swedish version of the Masonry Heater.
Local name for the Swedish version of the Masonry Heater.
Mortar used for general masonry work until the beginning of the
20th century. Usually one portion of lime to 3 sand.
A horizontal beam used to traverse an opening. Can be of stone,
iron, refractory concrete, or commune concrete.
Load Relieving Lintel
A lintel used to transfer compressive force, away from a potential
The widened area of the smoke path directly beneath each side
channel. There are three manifolds in a contra-flow core; left and
right side manifolds and a rear manifold running beneath the back
portions of the fire box.
A solid contact between two otherwise separate, rigid materials,
causing the possibility of one having a mechanical action on the
other due to thermal expansion.
Korean domestic version of the hypocaust having the form of a
ceramic sitting or sleeping platform. The Ondol is still used in
Korea today though most are fired with oil or gas.
The name given to the method of delivery for primary combustion
air, in which it is directed onto the wood load either laterally
or from above. The distinction being that no air rises through a
grate beneath the wood load.
Local name of the Polish version of the masonry heater. Built by
Russian name for the Russian domestic masonry oven. Built by a
Prefabricated Masonry Heater
Heater completely prefabricated, i.e. core and facing.
Prefabricated Refractory Core
Refractory core that is entirely factory made, consisting usually
of castable refractory concrete modules. Can be installed by non
Primary Combustion Air
Air drawn in to the fire box, usually from an intake in the facing
below the fire box door, which feeds the primary combustion of the
wood load. Primary air makes up most of the flow in the smoke
The small fire lit when the heater is being used from a cold
start. These fires bring the heater slowly up to operating
temperature, avoiding thermal shock.
The interior portions of a masonry heater, which enclose the smoke
path. Usually, though not necessarily, made from refractory brick
A general name user to describe stoves built throught the former
Soviet empire. Built by a Pechnik. Local names include petch,
Ignition and combustion of unburnt gases, during, and immediately
after primary combustion.
Secondary Combustion Air
Air drawn into the fire box, usually through an intake in the fire
box door. This air bypasses the primary combustion, travels across
the fire box ceiling and mixes with the smoke and flame to nourish
Secondary Combustion Chamber
Chamber above the fire box, connected to it by the throat, where
secondary combustion of the flue gases takes place, before the
gases flow into the side channels.
Secondary Combustion Chamber Oven
Upper Chamber Oven
Auxiliary oven taking up space within the heaters upper chamber.
Having a loading opening on the front or rear face of the heater.
See Through Heater
A heater with a firebox loading opening on both front and rear
face. Generally considered to be slightly less efficient than a
heater with only one fire box loading opening.
Semi prefabricated refractory core
Refractory core containing some precast modules of refractory
concrete, but necessitating the laying of some fire brick during
Brick that are layed face down i.e. on edge, rather than bed down.
An incurable lung disease contracted du to the long term prolonged
exposure to Suspended crystalline silica.. Note In France it is
said "Une bonne fumist est mort a 50 année".
Gasket of fire proof material used to inhibit the passage of smoke
from one portion of the heater to an other.
Hood or funnel in masonry or metal, used to draw smoke together
towards and into a chimney. Found on the front of direct fired
The path taken by the draw of the system through its self.
Beginning at the primary air intake door and ending at the top of
Soba de Terracota
Local name for the Romanian version of the masonry heater. Built
by a Sobar.
Actual Name: Sodium meta-silicate, Na2SiO3
Used as a bonder (hardener) in refractory mortars. Available in
dry or liquid form. A-Z Index
Openings giving access to the manifolds. Usually fitted with cast
The disintegration and loss of the exposed surfaces of a material.
A layer of insulating material placed between two dense conductive
materials with the intention of impeding thermal transmission.
A solid bridge allowing the conduction of heat from one dense
material to another.
The cyclic rise and fall in temperature which occurs during and
after each fire.
The destructive action caused on a material that is brought up to
temperature too fast, or unevenly. The main enemy to the longevity
of the masonry heater.
The detrimental effect of a material that is saturated,
accumulating heat faster than it can transfer heat, resulting in
cracking and warping.
The natural tendency for hot air to rise as it is displaced by
Point at which the fire box ceiling narrows, compressing the
gases. Usually precedes the upper expansion chamber
Top Down Burn
Name used to describe the manner in which a fire is layed, with
the large wood on the bottom, medium wood above that and finally
the paper and kindling layed on top. The fire is lit at the top
and burns slowly from the top down.
The total efficiency of the appliance, of which combustion
efficiency is on a part.
The measure of a material’s capacity of thermal transfer over
The name used to describe the manner in which primary combustion
air enters the fire box via a grate in the fire box floor.
The name given to a masonry stove which is connected to it’s
chimney at the top of the stove