Hearth bricks

[klaatu]

Greetings all,
I have noticed that most of the builders will lay out thier floors and then
build the dome on top with the hearth bricks sticking out. Would I not save
some of my heat if I stand up my first course on the percrete and not on
the hearth bricks? How about I put the bricks on top of the hearth bricks
but I Cut the hearth bricks so they don't stick out passed the first course?

I know that this sounds picky but it would be a bear to change later and
anything that helps keep the heat inside is good.


Rick,
<klaatu22@hotmail.com>
A long haired, over-fed, leaping gnome.

[james]

Re: Hearth bricks

Hey Rick,

You can definitely build your oven dome directly on the perlcrete layer, and it will be more efficient. A number of builders have done it that way, and the precast FB ovens all work this way. Do a search on a thread by Paulages. He built his dome that way.

Thinking about it, we should add that option to the Pompeii plans. I guess I need to start building a list of changes -- like a bug report in software. Funny.

Anyway, good idea Rick,
James

[carioca]

Re: Hearth bricks

Quick supplementary question: haven't seen your latest plans, but what is the current thinking on under-hearth insulation?

I have been supplied with 1in (25 mm) thick CalSil sheets to place under the 2in (50 mm) hearth bricks. Should I perhaps, to be on the safe side, put a layer of Perlite concrete under the CalSil? If so, how thick should I make it?

I am at the stage of forming up for the hearth, and would need to allow for any additional Perlcrete in the formwork...

Thanks for any input!
Carioca

[dmun]

Re: Hearth bricks

I think one inch is a little skimpy. Most builders have used 4" of perlcrete or two inches of insulation board under the bricks. I think a couple of inches of perlcrete under your one inch board would keep heat from leaking into your hearth slab.

[carioca]

Re: Hearth bricks

Thanks, dmun, my firebrick 'kit' suppliers thought 1in was ample - anything more would be a waste of money... But I tend to go with your advice and allow for 2in of perlcrete under the insulation board.
Ciao

[Les]

Re: Hearth bricks

Hey Rick,

You can definitely build your oven dome directly on the perlcrete layer, and it will be more efficient.

James - what if the dome was started directly on the structural layer with the hearth bricks setting on top of the superisol product. Do you see a problem with that? And along those lines; the superisol dimensions are not conducive to a round oven. How are the pieces joined? ( I'm sure the answer is here somewhere but the information on this site is getting rather large :-)

TIA,

Les...

[james]

Re: Hearth bricks

Hi Les,
At some point you have to start relying on "searches" within the forum, or start "subscribing" to the threads that you want to follow. There are some forums out there with a million postings, and you have to work hard just to not get lost.

To your point, you can start the dome around the cooking floor, set directly on the insulating layer -- either vermiculite or SuperIsol. To make it works with SuperIsol, you just need to make sure the insulation is larger than the footprint of the dome. You can cut it and lay it out to maximize your usage. The SuperIsol has square edges, so you just piece and hold it together with the glue.

Does that work for you?
James

[Les]

Re: Hearth bricks

Got it - Thanks James!