How to build a pizza oven hearth



Round pizza oven hearth
In a wood fired pizza oven the hearth is the section upon which the fire is built and eventually the pizza is laid to be baked. Because the temperature of the pizza oven will gradually grow to very high temperatures (370°C / 700°F), the hearth must be made of special medium-density fire bricks, which are able to withstand high heat without cracking. Once the desired temperature is reached the fire is moved behind or to the sides of the hearth to make room for the pizza to be cooked directly atop the bricks. This hot surface helps create a pizza with a crispy bottom. Other foods such as steak are better cooked on a steel grilled placed over the embers of the fire, rather than directly onto the bricks.

Construction Steps

Step 1Build a foundation upon which the hearth will be placed. This is usually constructed out of steel-reinforced concrete topped with a layer of hearth insulation.
Step 2Measure and mark out the location of the oven hearth using a tape measure and chalk.
Step 3Create a mixture of fine sand and fire clay for the fire bricks to sit upon.
Step 4Spread the sand and clay mixture oven the foundation using a 1/4" (1 cm) square notched trowel.
Step 5Lay the center most fire brick of the hearth.
Step 6Lay subsequent fire bricks flush against the existing fire brick hearth.
Step 7Place fire clay mortar around the outer most edge to keep the fire brick hearth in place.
Step 8The dome of the oven can then be constructed out of cob or brick.

Constructing the Hearth

The hearth will consist of a level area of clean flat fire bricks, placed atop a level bed of sand and fire clay. It will be the final true cooking surface of the oven and so it is imperative that the bricks used in its construction be of high quality, flat and clean. The purpose of the fire clay in the sand mixture is to improve stickiness, insulation, and heat retaining ability. Cement, however, should be avoided in the under-hearth mixture.

Measure and Mark the Hearth

Before constructing the hearth be sure to measure and mark out the location of the oven center and walls on the foundation surface. You can do this by using a tape measure and chalk to locate the center of the oven; but be mindful of the thickness of the oven walls (generally 8" or 20 cm), the vent landing (minimum 6"or 15cm), and the oven landing (minimum 6" or 15cm). Don’t forget to mark out the following:

  • internal vault area
  • perimeter of the oven walls
  • the oven door
  • and the outside of the decorative vent landing.

Additionally, the measurements will be affected by the shape of the oven you choose.

Hearth Area

Depending on the type of oven built, the fire bricks laid for the hearth may either be placed within the oven in either a circular or rectangular shape. The bricks may also be placed as an entire layer over the total foundation surface.

Building an igloo oven can be challenging in this respect as multiple small fire bricks will need to be cut to create the circular shape. As an alternative, the dome oven may be constructed, which requires less cutting, and the dome may be built as a circle over the flat hearth leaving fire bricks exposed around the perimeter. The disadvantage of this approach is the increased expense of utilizing extra fire bricks, and the implications of heat absorption and dissipation through the hearth under the oven wall insulation. Generally, either option is acceptable, and depends on the builder’s skill and aesthetic goals. It is recommended that fire bricks be laid dry on the hearth as a test, before the underside sand and clay mortar is applied.

Hearth Bed Mixture

The sand bed may be made from either plain sand, a dry sand and fire clay mix, or a wet sand and fire clay paste. If using sand and fire clay the mix should be created in a 1 : 1 ratio.

SandFire Clay
11

Dry Mixture

To construct the hearth using dry mixture, you will need to begin by placing refractory fire bricks on a thin layer of fire clay and sand (sieved) to remove any particles/pebbles.

A few things to keep in mind for this part of construction:

1. This layer should be about 1 inch (2.5 cm) deep.

2. At least half a bucket of pure sand without impurities is needed.

3. Impurities/pebbles in the sand, if any, will prevent proper leveling of the hearth.

4. Begin by screening the sand to a flat surface with a builders level, or a long flat piece of wood.

5. Depending upon the foundation, you may need to create a box out of wood specifically for the purpose of helping create a flat surface with the sand.

Wet Paste

If using a wet paste, it should be applied with a 1/4"(1 cm) square notched trowel. Here are a few things to note during this process:

1. These trowels are commonly used by tillers when laying ceramic tiles.

2. Mix the sand and fire clay thoroughly and add water to make a workable, sticky mortar type mix.

3. This mix should not contain cement.

4. Spread the paste on the concrete slab with the plastering trowel in a zigzag motion.

5. Trowel the sand and clay mix onto the makeshift oven hearth, and then lay the firebricks from the center.

6. As with other processes, this should be done without material placed in between the fire bricks.

Laying the Fire Bricks

Pizza oven hearth
The bricks for the hearth should be laid atleast 48 hours after the concrete slab dries. Gently place one fire brick in the direct center of the oven hearth, atop the sand mixture. Do not push down on this brick, as you place other bricks to create a level. Place the next fire brick at the edge of the first brick, leaving no gap. Gradually add additional bricks, by placing the edges together, and slowly sliding the brick down in place. Do not slide the brick over the sand, as this will push sand between the bricks, creating a gap. If the new brick is not level with the first, slightly press down on the new brick to level it. This can be accomplished by hand, or very gently with a rubber mallet. Continue to place fire bricks butted up against the existing bricks, without leaving a gap. Level the new bricks with the existing bricks, and check with your finger to identify any discrepancies. Once all the bricks have been laid, use a builders level to identify if any sections are not flat. Use a rubber or wood mallet to gently flatten sections which are out of alignment. Begin with the joints with the greatest differences ('lips') gradually moving to the most minor. If minor unevenness or catches exist which cannot be easily removed by leveling, these can be removed at a later date by grinding once the hearth has fully set.

Brick Pattern

Ideally, bricks for the hearth should be laid in a diagonal offset, or herringbone pattern, so as to reduce the number of straight joins created. These joins create the potential to catch on tools such as oven rakes and peels. If these joins are placed diagonally to the entrance of the oven, this will reduce the likelihood of catches. Mortar or grout is undesirable between the laid fire bricks, as it will increase the size of gaps, creating problems. In addition, larger fire bricks can be used to improve the hearth condition: they will further reduce the number of hearth joins and catches.

After the Fire Bricks are Laid

Once the fire bricks have been laid for the surface of the hearth, it is now time to place a small amount of fire clay mortar around the perimeter of the bricks to keep them in place with the foundation below. The mortar only needs to be applied onto the outermost brick. Once it has set, the hearth is now complete, and construction of the brick or cob dome may begin.

Common Questions

Can I use normal red builder's bricks for the hearth?

It is strongly recommended that you don’t. The hearth of the oven will experience extreme temperatures, and will need to be both structurally and chemically reliable, as it will come in direct contact with cooked food. Fire bricks are constructed specifically for the purposes of tolerating high heat, has good heat absorption properties, in addition to low porosity. For these reasons, bricks will survive the heat fluctuations, and resulting expansion and contraction experienced. Red builder’s bricks, however, are not built to tolerate high heats, and would gradually fail over time as the oven is used: cracks may form and bricks would even begin to flake off into the pizza base. Eventually, the heath will become uneven and unusable. In such a case, the entire oven would need to be rebuilt.

Can concrete be used for the hearth?

The answer is yes and no. Concrete, if made of refractory products, such as refractory cement, fire clay, or crushed fire brick grog, may be used for building both the oven hearth and dome. If a suitably quality mixture is being utilized, the concrete created may be able to handle the high temperatures and resulting fluctuations without any issue. This type of hearth, however, is not generally recommended: the potential for cracks and flakes is high due to fluctuations and the low tolerance to structural movement. While fire bricks which are laid with natural space, may allow for minor movement, concrete does not. When laying the concrete, care should be taken to utilize the correct amount of water, and permit the minimum curing duration.

Should I use mortar or grout between the hearth bricks?

Mortar or grout should never be used in the construction of the hearth. The fire bricks should be butted up against each other, without any adhesive. The join created is thus called a butt join. And although it may seem unstable, the remaining oven dome and construction developed will prevent movement of the bricks. If grout or mortar were used: this would prevent a stable, flat surface from being prepared. The high temperature will cause the adhesive material to crack and flake, leading to an uneven surface, and allowing foreign material into the raw food place into the oven. This will lead to an uneven surface, causing snags. Only clean fire bricks should be placed directly upon a level base of sifted sand and fire clay to create the hearth.

Ymullaji

Card image cap
Insulating dome pizza oven

The materials you use to build your oven determines how long the oven will last. The material of the...

Dome wall thickness

The thicker the walls of a wood fired pizza oven the greater the thermal mass the oven wil...

Using castable refractory cement between bricks?

Hi, newbee "mason" here. I have castable high temp mortar that I tried to use to butter between the ...

How to clean a brick hearth

What is the best type of bristle brush to clean the brick hearth in my Wood Fired Oven?

Card image cap
How to cook with a wood fired pizza oven

Further information: How to build a pizza ovenCooking a pizza in a pizza oven is always a fun e...

Card image cap
How to build a pizza oven hearth

Round pizza oven hearthIn a wood fired pizza oven the hearth is the section upon which the...

Card image cap
Purchasing a pizza oven

Further information: How to build a pizza ovenA pizza oven may be either built from raw materials or...

Card image cap
Types of cement

Further information: How to build a pizza ovenWhite cementThere are several ordinary cements in...

Card image cap
How to cook steak in a pizza oven

See: How to cook with a wood fired pizza oven1" (1 inch) = 2.5cm.Thickness1/2"3/4"1"1 1/4"1 1/2...

Card image cap
How to build a wood fired oven door

Further information: How to build a pizza ovenA door is a useful component of any tradition woo...

Card image cap
How to build a pizza oven shelter

Pizza oven shelterWhen building a pizza oven in an external location, it is important to c...

Card image cap
How to fire a wood fired pizza oven

Further information: How to build a pizza ovenWhen starting the initial fire in the oven be sur...

Card image cap
Fire bricks

Fire bricksFire bricks are an essential material in the building of a long-lasting, effective pizza ...

Card image cap
How to clad a pizza oven

Further information: How to build a pizza ovenCladding of a wood fired oven is the final layer ...

Card image cap
Build a pizza oven foundation out of brick

Building a pizza oven foundation out of brick starts with preparing the location. Fir...

Card image cap
Types of wood fired pizza ovens

Further information: How to build a pizza ovenBarrel VaultBarrel vault ovens are usually made o...

Card image cap
Common problems with pizza ovens

Further information: How to build a pizza ovenWhy my oven is not hot enough?The temperature pot...

Card image cap
Sourcing materials for building a wood fired oven

Sourcing materials for building a pizza oven can be difficult due to the types of material...

Card image cap
Pizza oven plans

A number of building plans exist due to the wide range of techniques by which a wood fired pizza ove...

Card image cap
What is oven cladding

Oven cladding is the process of applying a mortar or mud material to a wood fired oven to create a t...

Card image cap
Wood fired pizza oven building plans

Traditional wood fired ovens are notoriously challenging and fun to construct, and unique in charact...

Card image cap
History of pizza ovens

Wood-fired pizza ovens have long been existent for thousands of years. This type of oven has be...

Card image cap
Igloo dome vs barrel vault dome pizza ovens

Generally the determination of building an igloo dome or barrel vault pizza oven...

Card image cap
How to Build a Pizza Oven

A traditional wood-fired pizza oven, or more commonly known as masonry oven, is a type of ...

Card image cap
Building plans for a 42 inch igloo brick pizza oven

42inch pizza ovenBuilding plans PDFBuilding plans for a 42 inch igloo brick pizza oven.pdfFurther in...

Card image cap
How to install pizza oven insulation

Further information: How to build a pizza ovenThe insulation of a wood fired oven in its constr...

Card image cap
Different Bricks and quality testing methods

How to test good quality bricks!Brick is one of the important materials in making pizza oven. There ...

Card image cap
Fire brick

Fire bricksFire bricks are an essential material in the building of a long-lasting, effective pizza ...


More Forum Threads