Clay oven advice!

[Ricky1989]

Hi all !! This is my first post, I recently purchased a small pizza oven made from clay and various other insulating layers, however upon lighting this oven I am thinking that the flue is 1) too small, 2) set too far back! So my question is, what would be the easiest way to extend the doorway out to create an arch and install a 4” flue?? Please see attached photos, thanks for your time!!

[david s]

Hi Ricky,
most ovens are a bit smoky when new, until they are purged of moisture. Judging by the amount of smoke staining on the front it looks like you have a problem. This could cure itself as the oven is run in or it may be inadequate design. You don’t say what size your oven is, but a 4” flue is only adequate for an oven underaround 18” in internal diam IMO. My ovens are21” and run a 5” flue with a funnelled entry, which works extremely well. Looking at your pic shows the oven mouth with no rebate and an entry to the flue pipe actually inside the oven which does not work as well. This design makes retained heat cooking impossible unless you have a damper to close the flue pipe or block it off at the top. OK if you only want to cook pizza, but most of us quickly graduate to roasting and baking all kinds of other stuff pretty quickly.
Hard to tell from the pic but it appears that the floor is either uninsulated or it’s extremely thin in which case you might be having trouble getting the floor hot enough and maintaining enough heat in it.

[Ricky1989]

Hi, thanks for reply, I’ll get internal diameters tomorrow, and the floor base is made from 63mm thick firebricks. I think the air flow is badly designed.

[UtahBeehiver]

Do you know if the 63mm firebricks are insulated underneath. Firebricks themselves do no have the insulating properties that David is talking about.

[Ricky1989]

The firebricks are sat on 50mm of concrete

[david s]

The firebricks are sat on 50mm of concrete

You’’ll never get the required temperature in the floor unless it is insulated between the concrete supporting slab and the floor bricks. In addition the dome itself should also not be sitting on the concrete. Suggest you remove the dome and floor bricks and place 50 mm thick calcium silicate board on the concrete on top of which you place the dome and floor bricks. Then seal around the edge of the exposed board to prevent weather getting at it.
Were there no installation instructions?

[UtahBeehiver]

Have to second David's recommendation. The concrete acts as a heat sink drawing away the heat that is in the firebrick floor. In your original post you mention "other" insulating layers, can you give us a little more insight on this. Insulating the dome should also be considered.