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johnrbek 03-25-2007 01:17 PM

Space between hearth floor and dome wall?
Quick question.

The first chain of bricks in my dome will stand on end around the outside perimeter of the hearth floor...the hearth floor has already been cut to the shape of a circle...

I thought I read somewhere that I should leave some space for expansion between the hearth floor and that first chain of bricks (on end).. Is this correct? If so, how much space?



james 03-25-2007 01:57 PM

Re: Space between hearth floor and dome wall?
Hi JB,

Good catch. Just enough for ash to fall in, and to allow for the dome and floor to expand and contract at different rates. You don't want the floor pushing out on the dome. 1/8"-1/4" will do it.

This is something else for the next release of the plans. We have not described how to build the dome around the cooking floor (not on it) in the current set of plans, but we should in the next rounds. I guess we should add it to the Recommended Changes page.

Hendo 03-25-2007 05:42 PM

Re: Space between hearth floor and dome wall?
So it's not necessary to fill that gap with sand, or a sand/fireclay mix? I thought I read about someone doing this. Not that I want to have sand granules on my pizza though!

johnrbek 03-25-2007 06:49 PM

Re: Space between hearth floor and dome wall?
Thanks James!

Here's another one... for the folks who have gone with super isol, insblok 19, or other insulating boards, did you still have to put down the fireclay/sand mixture down to get a good even layer of hearth bricks as is done with the perlcrete insulating layer?

I've noticed, as many others have, this insulating board is generally pretty thirsty and want to avoid it getting wet. I supposed if you still needed the fireclay/sand mixture that you might want to use it dry...

What's everybody doing when it comes to this?


Hendo 03-25-2007 09:06 PM

Re: Space between hearth floor and dome wall?

Like you, I don't want water to get into my Cal Sil boards, so the (otherwise excellent) idea of using a dry fireclay/sand mix and dousing the lot after achieving a level floor doesn't appeal. I was thinking of using dry refractory mix and just leaving it. Or perhaps a fine washed sand may be just as good as dry refractory.

My only concern is that while the dome will be fixed to the insulation with refractory mortar, should the floor be similarly fixed, or can it remain free to float around on a bed of sand, or dry fireclay/sand, or dry refractory mix?

Comments, please!


dmun 03-26-2007 06:48 AM

Re: Space between hearth floor and dome wall?
I think play sand would work fine as a leveling medium. You are way on the other side of brick and insulation from the fire, which isn't that hot anyway. Using refractorys where it's hardly warm doesn't seem like a good use of resources.

johnrbek 03-26-2007 07:13 AM

Re: Space between hearth floor and dome wall?
Hendo... for what it's worth, I spoke with a refractory dealer and he said he didn't see an issue not gluing the insulating boards down... with the weight and exterior mortar and/or insulation + enclosure (if doing one...) again, for what it's worth... I won't be gluing mine down. I'm using insblok 19 and it's kinda brittle/fragile... I would think even if you glued it, under pressure it would probably just break away anyway...

dmun.. I've got a bunch of fireclay (probably sufficient to mix with sand) from cutting firebrick... was just thinking of mixing that dry with the sand.. to make it a little more easy to work with.. that make sense or do you think I should still just go with sand?? I'm gonna see if they lay flat without anything first.. will report results...



jwnorris 03-26-2007 07:57 AM

Re: Space between hearth floor and dome wall?
After several attempts to get the SuperIsol board wet enough to allow me to spread some Refrax mortar [unsuccessfully, I might add], I can to the realization that the components of my Casa 110 were of such weight that they were not going anywhere. As I had leveled the base structure, I was not concerned about the floor being level.


Hendo 03-26-2007 11:10 PM

Re: Laying a floor on Cal Sil board
Oops! I posted a response on another thread in error, although this one seems to have changed direction somewhat ...


Cheers, Paul.

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