The Concrete Base Slab

For the purposes of this context, we will refer to concrete slab that the pizza oven sits on as the 'hearth' or it is sometimes referred to as a plinth.

A hearth is the slab or flat base that the oven is built on and supports the oven.  It is almost always made from concrete. The compressive strength of concrete, its inflammability, low cost and life span make it an ideal product for the job. 

Never build an oven or fire on a wooden or flammable structure!  

The slab is usually 100mm in thickness and contains reinforcing mesh to give it structural strength.  We recommend using 50x50mm reinforcing mesh to create a very rigid floor but you can also use D12 rebar.  Most steel suppliers offer this mesh in 1.2x2.4m sizing.  

The size of the hearth is generally calculated around the support stand materials (such as concrete blocks), the total oven build width and any spare space you want around the oven.

For our kit sets add at least 150mm to the sides and rear of the cardboard mould dimensions.  For example the 800mm oven will require at least 1100mm wide hearth (800 +150 +150).

At the bottom of the page you will find the various sized oven illustrated on different sized hearths.  

Here are a few points to consider when designing your hearth:

  • It its best not to use flammable materials under an oven to support the concrete slab as the hearth can become quite hot in longer cooking sessions (despite insulation).  Use steel, aluminium or concrete.  
  • A landing (area out the front of the oven) makes your oven safer from pieces of burning wood rolling out and offers a place for drinks etc. 250mm is a good size.   
  • A work bench for preparing food is usually lower than your hearth height so quite often is built separately.
  • Consider using permanent outside boxing (like aluminium angle) as building and removing boxing for the hearth can be tricky and when formwork is removed the outside finish can often be quite rough with air pockets.  
  • Try and pour your hearth in place as concrete slabs are extremely heavy and hazardous to lift into place.  A bit more formwork avoids a whole lot of lifting hassle.  
  • Try to design the hearth so that it won't absorb a lot of rain water as this can seep into the oven.
  • Makes sure your stand is strong enough to hold all the weight of both the hearth and the oven.  A standard 800mm oven with hearth can weigh around 1 tonne.   

600mm ID oven on 900mm x 1000mm concrete slab

600mm ID oven on 1000mm x 1200mm concrete slab

800mm ID oven on 1100mm x 1200mm concrete slab

800mm ID oven on 1200mm x 1400mm concrete slab

950mm ID oven on 1250mm x 1350mm concrete slab

950mm ID oven on 1400mm x 1600mm concrete slab