The following are some common terms related to masonry and wood fired ovens that you may find on the blog or forums. This list is in alphabetical order. If you believe important terms are missing, please email Matt at email@example.com with your suggestions.
Abutment – Often confused with a Buttress, an Abutment is the structure supporting one side of an arch, or additional masonry that is used to resist the lateral forces of a vault. Commonly seen on segmental arches and Barrel Vaults.
Aggregate – the component (sand or crushed stone) of a composite material (mortar,concrete) that resists compressive stress and provides bulk to the composite material. Ideally, aggregate should have a wide variety of sizes (graded) within the composite.
Arch – a structure that is over an opening and that supports a wall or other weight above the opening. Common Types: gothic (pointed), semi-circular (roman), segmental.
Barrel Vault Oven – or Tunnel Oven, this shape is as its name implies…a barrel vault. The cross section of this oven is a segmental arch and the footprint is rectangular, with straight side and back walls.
Bed joint – a horizontal joint on which a masonry unit is laid.
Black oven – an oven that is heated by burning wood within the chamber. Food is cooked in that same chamber while the fire is still going, or in the heated chamber after the fire and coals have been swept out.
Bond (masonry unit)– pattern of laid masonry units; adhesion between mortar and masonry units; tying together two or more wythes of masonry walls by over lapping masonry units.
Bond (cementitious) – the mechanical connection between masonry units or stone to mortar and concrete, cladding layers, or finishes to substrate.
Brick, masonry, or “cast” oven – an oven consisting of a baking chamber made of fireproof material.
Buttress – A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall. Buttresses are fairly common on more ancient buildings, as a means of providing support to act against the lateral (sideways) forces arising out of the roof structures that lack adequate bracing.
Castable – refractory material that is mixed with water and poured or rammed into a mold. Hydraulic set.
Cement – manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients. Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore. These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement. Withstands temps up to 500 degrees Celsius ( 932 degrees ) before thermal damage occurs. Suitable for use in fire mortar for wood ovens.
Centering – Forms which support the weight of an arch during construction. Also called False-work. Common oven building types: Rigid foam form, sand.
Chimney – masonry or framed structure around the flue to which decorative finish is applied or installed. Insulated Stainless Chimneys contain both flue and outer shell.
Cladding – a shell of mortar, stucco or concrete. Can be added to create additional thermal mass, enhance structural stability, or act as a substrate for veneer, tile or stucco.
CMU – often called cinder block, it’s a unit made from concrete that comes in a number of sizes, solid and hollow.
Component mix – commonly called ‘Home Brew’ mortar. It consists of masonry sand, Portland cement, lime and fireclay. Proportions of each component will vary builder to builder, project to project.
Compressive Strength – capacity of a material to withstand pressure. Most stone and concrete have high compressive strength, but low tensile strength.
Concrete – formed when water, cement powder, sand and aggregate is mixed together.
Control joints – planned cracks which allow for movements caused by temperature changes and drying shrinkage. In other words, if the concrete does crack-you want to have an active role in deciding where it will crack and that it will crack in a straight line instead of randomly.
Crust – sometimes referred to as the cornicione. The puffy outer edge of a pizza.
Curing or “setting” – a series of hydration chemical reactions. The constituents slowly hydrate and crystallize; the interlocking of the crystals gives cement, mortar and concrete its strength. Often the word ‘cure’ used to describe the drying process of a new or wet oven. This is inaccurate because the material (except the mortar and cladding) has already set before construction begins. See: Drying (oven)
Diamond blade – a saw blade with diamonds imbedded in a metal matrix. They can be segmented (aggressive cutting) or continuous rim (better for softer material) and be used wet or dry according to specifications.
Dome – a round structure made of either curved segments or a shell of revolution meaning an arch rotated around its central vertical axis. If viewed as a cross section, a dome is a series of arches. Common Types: hemispherical (Pompeii) or elliptical (Neapolitan)
Drying (oven) – the process that involves applying increasingly higher degrees of heat to the oven masonry to dry and drive out water, either from the construction process or from intrusion. This process is often called curing, but it does nothing to change the composition or nature of the masonry, mortar or concrete other than dry it out.
Efflorescence – occurs when water saturates masonry walls and dissolves water salts within the mortar and brick. These salts are deposited on the surface of the masonry as the water evaporates. There are several possible sources of moisture, including water penetration, condensation from moist air or water from below the structure.
Elliptical Dome (Neapolitan) – a dome oven with a circular footprint and an elliptical arch cross section. This is one of the types that are favored by traditional Neapolitan oven builders and pizza makers, but it has the range of an all purpose oven. The other is the Segmental dome (arch) This shape has more lateral thrust than a Hemispherical Dome.
Lightweight Expanded Clay Aggregate – (LECA) clay heated in a rotary kiln to form a light weight, air filled pellet. Used in traditional Neapolitan oven building as an insulator.
Expansion joint – vertical or horizontal joints used to separate masonry into segments to control cracking. Also see : Control Joint or Slip Joint
Fermentation – a step in creating baked goods where the yeast is allowed to leaven the dough.
Fire brick – built primarily to withstand high temperature, but will also usually have a low thermal conductivity for greater energy efficiency. Usually dense firebricks are used in applications with extreme mechanical, chemical, or thermal stresses, such as the inside of a wood-fired kiln or a furnace, which is subject to abrasion from wood, fluxing from ash or slag, and high temperatures. This is not a concern for wood ovens, so low duty bricks are the best choice, followed by medium duty fire brick.
Fire clay – a term applied to a range of refractory clays used in the manufacture of ceramics, especially fire brick. Fire clay is resistant to high temperatures, having fusion points higher than 1,600 °C (2,910 °F),
Fire resistant mortar – a mortar consisting of materials that are resistant to heat damage, but are not true refractory materials. Suitable for oven building, but it is not as durable as refractory mortar.
Flue – a chase made of masonry, clay liner or metal which is attached to a transition or shelf on top of the throat/vent area.
Hemispherical Dome (Pompeii) – a dome oven with circular footprint and a semicircular arch cross section. Typically has a high ceiling compared to an Elliptical/Neapolitan dome, and has less horizontal thrust. Popular oven shape for general purpose use.
GFRC – glass fiber reinforced concrete. Commonly used in designer and artisan concrete casting.
Header (Brick Orientation) – masonry unit that is bedded with its end facing out, with its width horizontal. This is the most common orientation for oven dome construction above the first course of Soldier or Sailor BRICK.
Head joint – the vertical mortar joint between ends of masonry units.
Insulation – fireproof or fire resistant material used to contain stored heat within the oven masonry. Examples are: ceramic fiber board or blanket, mineral wool,perlite or vermiculite, insulating concrete ( perlcrete,vermicrete)
Intrados – the interior curve or surface of an arch.
Infrared (IR) Gun – a device used to measure temperature from a distance.
Keystone – a wedge-shaped stone piece at the apex of a masonry vault or arch, which is the final piece placed during construction and locks all the voussoirs into position, allowing the arch to bear weight.
Hydraulic lime – is a general term for varieties of lime (calcium oxide), slaked lime (calcium hydroxide), used to make lime mortar which set through hydration: thus they are called hydraulic. A common part of the component mix (home brew)
Lateral Thrust (arch) – the horizontal force transmitted by the downward pressure of an arch.
Lime mortar – is a type of mortar composed of lime and an aggregate such as sand, mixed with water.
Lintel – a horizontal structural unit (beam) over an opening; support member over a door or window opening.
Masonry – that which is built by a mason; anything constructed of the materials used by masons, such as stone, brick, tiles, or the like. Masonary is not word!
Masonry veneer – walls that consist of a single non-structural external layer of masonry work.
Mortar – used to bind building units together, fill and seal the irregular gaps between them. It is a web of masonry reinforcement if it is done properly. Often called ‘mud’ it is much more than that.
Neapolitan Oven – When build in the tradional fashion, designs include an elliptical and segmental arches, a entry-front vent, center chimney, handmade clay brick and tile, tuff and expanded clay used for insulation.
Oven entry – the area directly in front of the oven opening.
Portland cement – the most common type of cement in general use around the world, used as a basic ingredient of concrete, mortar, stucco, and most non-specialty grout.
Proofing – the final dough rise step before baking, a specific rest period within the more generalized process known as fermentation.
Reinforcement – added to cladding, structural slabs and castables to create tensile strength. Rebar, welded wire mesh, hardware cloth, chicken wire, glass fiber and stainless steel needles are examples.
Refractory – materials that must be chemically and physically stable at high temperatures. Depending on the operating environment, they need to be resistant to thermal shock be chemically inert, and/or have specific ranges of thermal conductivity and of the coefficient of thermal expansion.
Refractory mortar – mortar containing refractory materials such as alumina and retains its durability and strength at high temperatures.
Rowlock (brick orientation) – brick that is bedded with its end facing out, with the width vertically oriented. Often mistakenly referred to as a Soldier, but the rowlock is only half the height. Often used as the starter course on Hemispherical Ovens.
Sailor (brick orientation) – brick that is vertically bedded with it width facing out. Creates a thinner massed wall, but it is less stable than a Soldier brick.
Slip joint – a joint made between an older and a newer masonry wall to form a continuous surface,masonry at the end of the newer wall fitting into a vertical groove cut in the end of the older wall. Also see : Control Joint or Expansion Joint
Soldier (brick orientation) – brick that is bedded with its side edge facing out. Creates a more stable base course than a Sailor course and more thermal mass, because the width is adjacent to the face of the wall. Common starter course for lower domed ovens like the Neapolitan Oven.
Spall – flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of corrosion, weathering, cavitation. Spalling and spallation both describe the process of surface failure in which spall is shed.
Springer – an architectural term for the lowest voussoir on each side of an arch. It is the bottom-most element of the arch.
Stretcher (brick orientation) – brick set with its longest edge facing outward and horizontally.
Structural clay tile – hollow masonry building units composed of burned clay, shale, fire clay or mixtures thereof. Neapolitan oven builders commonly use them to build a squirrel tail flue transition.
Structural slab – the concrete slab or platform on which insulation and the oven itself are built upon.
Squirrel tail flue – a transitional flue that is built along the top ( or back on colonial bake ovens) of the oven and connects to the flue liner that rises from the center of the dome. The throats are extended beyond the face of the oven opening more than an oven with an entry that has a straight flue.
Stucco/render – a material made of an aggregate, a binder and water. Stucco is applied wet and hardens to a very dense solid. It is used as decorative coating for walls and ceilings and as a sculptural and artistic material in architecture.
Substrate – material surface that is behind or underneath a finished product, to which it is adhered.
Tensile Strength – maximum stress of a material before its breaking point. Concrete has relatively low tensile strength, thus the need for reinforcement.
Tension Ring – a steel ring, chain or cable implemented to contain lateral thrust. Commonly seen on Neapolitan oven builds because of the low arch.
Thermal break or thermal barrier – an element of low thermal conductivity placed in an assembly to reduce or prevent the flow of thermal energy between conductive materials. On oven builds, they are incorporated between the entry and oven opening. Technically, hearth floor insulation is a thermal break for the structural slab.
Thermal conductivity – is the property of a material to conduct heat, often denoted k, λ, or κ.
Thermal cycling – the process of cycling through two temperature extremes, typically at relatively high rates of change. It is an environmental stress test used in evaluating product reliability as well as in manufacturing to catch early-term, latent defects by inducing failure through thermal fatigue.
Thermal shock – occurs when a thermal gradient causes different parts of an object to expand by different amounts. This differential expansion can be understood in terms of stress or of strain, equivalently.
Tuff – A type of volcanic material made of consolidated ash. Used in building traditional Neapolitan ovens, it is soft enough to be hewn to size and shape with a hatchet. Most commonly used to build the base of the oven.
Vault – an architectural term for an arched form used to provide a space with a ceiling or roof. A vault is deeper than its width. Common Type: barrel vault.
Vent/throat – the opening above the oven opening, where exhaust gas and smoke exit from the oven chamber.
Vitrification (vitrify) – the process of melting that clay goes through as it is fired to maturity ( hardness). Range for vitrification is 1950* – 2455*
Voussoir – a wedge-shaped element, typically a stone or brick which is used in building an Arch or Vault.
Unit – a single piece of stone, brick, concrete, etc, in its natural state, cut, formed or cast.
White oven – an oven heated by heat transfer from a separate combustion chamber and flue-gas path.
Wythe – a vertical wall or tier of masonry units one-unit thick. The thickness of masonry separating flues in a chimney.