firebrick base question

[caspian]

I am in the process of completing my patio. So far, I have build a fireplace and am now starting my pizza oven.

My question is, for the base layer of the pizza oven, I am planning on putting the firebricks on their sides to increase thickness. Should I use mortar between the bricks or just stack them so there is no space between them?

Also, is there any additional insulation needed below the firebrick or will 4" of firebrick be enough?

Below is a picture of the fireplace. The outside isn't finished in stone yet. I will do that when i complete the pizza oven and do it all at once.

[caspian]

Re: firebrick base question

after reading the forum more (this is my first time here) i realized i need more insulation at the base. I will go with 3 1/2" vermiculite/portland for under the firebrick. Anymore than that, i will be getting too high.

[Laku]

Re: firebrick base question

If you use vermiculite/perlite it should be atleast 4". You options are to make the floor not as thick to have enough room for the insulation. Or to use ceramic insulation board that can be thinner for the same efficiency. Insulation is not the part where you wan't to skimp on.

My question is, for the base layer of the pizza oven, I am planning on putting the firebricks on their sides to increase thickness. Should I use mortar between the bricks or just stack them so there is no space between them?

Don't mortar them. Just stack them without any spaces.

If you plan on building the floor inside the dome then you also need to leave a gap between the dome and floor to leave some room for the floor to expand. If Not then just stack them and start building the dome.

[mrchipster]

Re: firebrick base question

If it were me I would trade more insulation in the floor for less brick floor thickness, I have 2.5 inches of vermicrete covered by 2 inches of ceramic board and I wish my floor insulation was thicker. I am not concerned about my bricks laid on the thin side.

I also agree that you do not mortar the floor bricks to anything, themselves or to the dome.

I see you have splits over the entry of the fireplace, on the ceiling... In an arch type configuration, What is, or will, be holding them up?

Chip

[GianniFocaccia]

Re: firebrick base question

and I wish my floor insulation was thicker

Hey Chip! Is your support slab getting hot? Do you think you're losing residual heat through the floor?

[caspian]

Re: firebrick base question

Here is the base. I was afraid that it would be too high, but after mocking up the height with 8.5 inches (4 of vermiculite and 4.5 of the brick) it will be o.k.



The splits are held by the mortar (2 parts portland, one part fireclay) So far so good. Should I expect them to pop? this is my first time around and am learning as i go (as you can tell from my posts). I am spending a ton of time looking at threads and already know 10X more, but still 90% less than most of you.

[mrchipster]

Re: firebrick base question

Hey Chip! Is your support slab getting hot? Do you think you're losing residual heat through the floor?

John,

Yes seeing a 20 - 40 degree temperature rise over ambient for the ceiling of the wood bin below the oven after long hot burns slab thickness is 4 inches of concrete with .5 inches of cement board. Quite a bit of mass to bring up 40 degrees. Ambient has been averaging 65-70 and the ceiling has been up to 120 on 90 degree days, The wood bin is usually full so there is not much air movement in there to dissipate the heat -- but I wish I was not losing so much. I think this heat loss may be worse in the winter when it gets below zero.

I am sure the floor is dry because there is no access point for water and I see no signs of moisture. The roof is sound and looking inside the storage area also shows no moisture. In addition I have been keeping the oven hot now for 2 months never been under 200F and usualy fired to over 600 at least once a week, and have not seen any indication of degrading or improving performance.

Just another reason to insulate more than you think you should.

Drawing is sketch-up of layers.

Chip

[GianniFocaccia]

Re: firebrick base question

Just another reason to insulate more than you think you should

Thanks for the report, Chip. I though I was over-insulating when I put 2" of board on top of 3.5" of vermicrete. Now it appears that it's really more like, uh, minimum.

[mrchipster]

Re: firebrick base question

Thanks for the report, Chip. I though I was over-insulating when I put 2" of board on top of 3.5" of vermicrete. Now it appears that it's really more like, uh, minimum.

John,

You do not get quite so cold there so not as much of an issue. But I think you will be glad you have that extra inch especially with the soapstone.

Just remember there are ovens out there with no insulation under the floor. Just think how much those floors contribute to "Global Warming" and de-forestation.

Chip

[mrchipster]

Re: firebrick base question

The splits are held by the mortar (2 parts portland, one part fireclay) So far so good. Should I expect them to pop?

I think the ones on the wall are fine but the ones on the ceiling arch will be prone to Newtons law of Gravity at some point in the future.

Chip