Updated: May 5
Skill Level: Skilled Handyman-Basic Professional
Time to build: 3-5 days with setting times (9-12 hours in total time)
Curing time for cement: 2-3 months
Let's discuss the designs and specifications of building a great pizza oven hearth cooking surface. This blog explores the designs and requirements to making the perfect hearth for any outdoor woodfire oven and gas fired oven. After this we will show you how to make it yourself.
I cannot over-emphasize the importance of getting this right. Many people ruin their experience using outdoor ovens by getting this important step wrong.
To get the best balance between efficiency and performance we need to ensure we do not make our hearth too thick. We also need to ensure we have insulating properties within the hearth to retain heat once your cooking surface is at the desired.
You want to be cooking between 160-250°C on the surface for cooking various pizza types.
Note: Our diagrams and images show a complete box setup, however, our focus is on the hearth cooking surface. Your choice of base and structure is entirely up to you. Just ensure your structure can handle the weight of your hearth.
Disclaimer: This instructional blog is a guideline only, you are responsible to ensure you are happy with all designs and local requirements from your municipal authorities. Please ensure your structure is strong enough to hold your oven and hearth.
This building guide is to be used in conjunction with our Piazza Hearth Build Kit to ensure your have the correct materials. If you want to supply your own materials this is fine as well.
These specific materials consist of the following:
KIM Water proofing additive for concrete
30mm Ceramic Fiber Blanket
Pyro Tape (for between oven and hearth around perimeter)
Granite Cooking Surface (30mm granite insert cut to correct sizing)
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General Materials you will need for the build, these can be obtained from your favorite hardware store.
18mm H3.2 Ply
8 x 75mm m6 bolts, double nuts, and double washers
5mm sharp chip gravel
General Tools Required:
Basic Hand tools (hammer, pencil, tape measure etc)
Angle Grinder with metal cutting disc
Mark out your site, build your base structure to handle at least 1000kg of weight.
Make sure your ground is not too soft as the weight of the project and the oven will compress the foundation. Ensure you have sufficient packing/footing.
Now lay your ply sheet over the cavity and prop the ply from underneath until your hearth has hardened. Ignore the need for support under the ply if you have a solid packed base.
Box out your hearth for the main concrete pour. Note: Remember to keep the pour level 50mm down from your final thickness to allow for the placement of the bedding mortar and the 30mm granite/tile cooking surface.
Place your steel mesh into the cavity and suspend it 50mm above the ply base using 50mm ply blocks
Place your ceramic fiber insulation blanket on top of the steel mesh
Pour 6:1 ratio concrete into the cavity.
Once the mix begins to congeal insert your 8 75mm SS m6 bolt, head down into the concrete so that the top of the shaft protrudes 30mm above the surface of the concrete.
Now screw the m6 nuts and washers onto the bolt to the top of the shaft. These will later hold your granite cooking surface when you bed this into the mortar later.
Make up a carboard template of the granite cooking top and trace this shape to the place you want it on your table top. Mark it with a knife in the congealed concrete surface.
Mix up your bedding mortar and wad it within the shape and place your granite onto the bedding, this will sit onto the bolts previously inserted.
Now add your top layer of render to the edges of the granite and bring it almost flush - recede by 1.5mm max. If your base hearth concrete has gone hard, you will need a good key grind with slots before you apply your top coat and edging render.
Create a 5° pitch from the granite edge to the edges of the hearth to ensure no water gets into your oven when it rains. See diagrams
Once your render has congealed, arise the edges to your desired finish.
IMPORTANT: Keep your project covered and sealed from rain and direct sunlight until it has cured and you have installed the oven on top of the hearth.
See Below, the octagonal cut out for our Piazza Granite Cooktops. You can refer to this is you would like to box out this shape before you pour your concrete.