uneven hearth Tools, Tips and Techniques Discuss uneven hearth in the Pizza Oven Design and Installation forums; 1 to 1.5 inches of insulating (vermiculite/portland cement mix) cement between supporting slab and firebrick. Whoa! Stop! That's not nearly ...

[dmun]

1 to 1.5 inches of insulating (vermiculite/portland cement mix) cement between supporting slab and firebrick.

Whoa! Stop! That's not nearly enough. 4" of vermiculite concrete is the minimum recommended. You should dig out your firebrick floor now, and either dig down to the support slab and put in 2 inches of refractory insulation board, or fill in the cavity to give you four or more inches of vermiculite concrete.

This is really important. It seems like a PITA now, but after your dome is built you have NO options to properly insulate under your cooking floor.

Forget about leveling your floor as it is. Your oven will never get up to heat with so little insulation.

[cecilB]

Ok. Thanks - "we" will start digging out!

Tim will be thrilled!

cecelia

[karl]

After pouring in the extra vermiculite level I think the easiest way to level the fire brick floor is to set the bricks in the moist (not wet!) vermiculite and give them the necessary tapping with a rubber hammer for best possible alignment/leveling before letting the layer dry out and harden.

Karl

[cecilB]

First of all, Thanks for all your advice - we are going to go ahead and take out the extra thermal mass of firebrick and fill in with the insulated hearth - I would still like to add extra thermal mass but maybe with the flatter firebrick...?

Second - what exactly do we use to lay the brick? Is there a specific name for the fireclay that is called for in the list of materials in the plans? Or is it the Heatstop 50?

Thirdly, I tried uploading a photo - it says it failed. Any suggestions there?
Thanks,
Cecelia

[Les]

Originally Posted by cecilB

First of all, Thanks for all your advice - we are going to go ahead and take out the extra thermal mass of firebrick and fill in with the insulated hearth - I would still like to add extra thermal mass but maybe with the flatter firebrick...?

Second - what exactly do we use to lay the brick? Is there a specific name for the fireclay that is called for in the list of materials in the plans? Or is it the Heatstop 50?

Thirdly, I tried uploading a photo - it says it failed. Any suggestions there?
Thanks,
Cecelia

Fireclay is not the same as Heatstop - that is the mortar us use for the brick. Any well stocked construction supply should have fire clay.

In regard to the photo, save it as a JPEG. There is a limit to the file size you can upload.

Les...

[cecilB]

It is a JPEG -

We started pulling up the thermal mass of firebrick and it is pretty soft stuff. And the stuff under the brick is still wet - this is after 2 - 3 weeks.
A good learning lesson, eh?
We'll just pour a whole new insulated hearth but I would still like extra thermal mass.
Mine is not JUST for pizzas - I have a pretty good bread business going here, that I won't keep up if I only have my two electric ovens to do all the baking!

And regular fireclay for the laying of the oven floor, but heatstop 50 for the mortaring of the bricks when we start on the dome, right?

Thanks
cecelia

[DrakeRemoray]

Correct, on Regular fireclay for laying the floor and heatstop50 (the drymix not in the tubs) for building the dome. You can also make a home brew mortar out of the fireclay and (what else is in there?), but the heatstop is easiest to use if you can afford it.

Normally we don't reccomend extra thermal mass, but since you are in the business of baking bread....

Perhaps you could lay the hearth bricks on their side (as opposed to flat). You can also add thermal mass to the dome by coating it with extra heat stop or home brew mortar.

Drake

[cecilB]

Yes, I was thinking of laying them on their sides, or buying the flatter fire brick...I think it would be better just to lay them on their sides.

I am in the business of baking breads - but not fully committed! How much longer will it take to heat up the oven - I'm not quite sure exactly all the specifics, but I'm guessing it goes like this - you fire the oven up to Really Hot and do the pizza, then by the time you finish the pizzas your oven is ready to take breads...then after that roasts?

Anyway, I will get to that when the time comes - at the rate we're going, I don't imagine this'll be done before winter!

cecelia

[dmun]

Refractory suppliers sell three inch thick firebrick, for that bit of extra thermal mass without a lot of extra work or expense.

[cecilB]

ok, we have successfully ripped out all the extra thermal mass of firebrick and most of the insulated hearth - We will build a form around the top, so there will be at least four inches of the vermiculie/portland mix.
And for the extrathermalmass, we will lay the bricks on their sides.

My hands are sore.

Cecelia