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Ollie 11-08-2008 07:14 AM

Cal sil board to replace Vermiculite
I have placed Cal Sil boards (from Darley refractories OZ) directly onto the concrete hearth. There is no layer of vermiculite mix under the boards. The boards are 25mm (1") thick, 1000mm x 610mm and cost 50 bucks each. You need four to cover the dome site. I have been assured that this thickness is sufficient to insulate the oven floor (75mm/3")fire brick from the concrete hearth. Any thoughts on this?

glennb 11-08-2008 01:06 PM

Re: Cal sil board to replace Vermiculite
I don't have an answer, but a similar question. Although you could have maybe got a better price from Johnny-the-oven-man from these forums for the Cal-Sil board. ;)

I am also planning to use the Cal-Sil board (50mm) between my oven bricks and the concrete hearth slab, but I also want to install a thermocouple.

The thermocouple probe is about 300mm long and i'll have it sticking up through the Cal-Sil board and into the floor of the oven between a couple of bricks, but it has a plastic handle thing on it, so what i want to know is will the Cal-Sil board be enough to keep the temps down so that the plastic handle and wire doesn't melt, or do i need to put some Vermiculite between them as well?

bbell 11-09-2008 11:37 AM

Re: Cal sil board to replace Vermiculite
Which brings up a question I had....!

Do you pour anything from the edge of the board to the edge of the supporting slab? Or do you cut the board to just fit the dome and let the rest of the materials come all the way down to the supporting slab itself?

Sorry if this is confusing.


Wiley 11-09-2008 01:00 PM

Re: Cal sil board to replace Vermiculite
Not confusing at all Bill. The plans seem to call for the insulation to go across the whole surface of the support stand. Many including myslef have modified the plans so that we are in fact only insulating the area that needs to be and the areas not needing insulation are filled with something like concrete. To me the vermicrete or other insulation needs to be contained and protected from any and all water intrusion. To run all the way to the edges seems to invite water problems IMHO.
You can see what I did on my stand and WFO on the thread "Steel Dome Oven".

pizzahead 11-17-2008 04:46 PM

Re: Cal sil board to replace Vermiculite
I had similar issue with my oven. I had a 1" cal sil board (purchased from Johnny the Oven Man in Mulgrave Vic) to insulate the oven hearth. After asking lots of questions I also went for 3" of vermiculite concrete as well as the cal sil board. Once your oven is built you cant put anymore insulation underneath it, and as everyone says you can never have too much insulation.


bbell 11-18-2008 11:50 AM

Re: Cal sil board to replace Vermiculite
Wiley, you get the prize for thinking outside the dome. Well done!
Jase, thanks and you're right, hard to go back and change.

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