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Barstool 04-27-2011 04:13 PM

Building error...Suggestions?
Suggestions welcomed...
I believe that (in my usual- "what the heck, if that doesn't work we'll just have to adapt and overcome"- method of buidling) I may have committed a gaff.
At the risk of being too in-depth: I am dealing with some space limitations so poured a concrete slab as large as my site would allow -roughly 6' wide X 5'6" deep. Atop this foundation was erected a block wall ending in an additional reinforced concrete 'pad'. Finally atop this pad a 5" layer of vermiculite/concrete mixed in the standard 5:1 ratio as the insulating hearth. My error, however is that I topped the entire top surface with the insulating concrete leaving no surface to build an additional 'retaining' wall that would provide space between (it) and the external oven wall to enclose insulation. (Poor description).
However, my belief is that as the igloo style build will sit well inside the outer dimension of the insulated hearth, I will be able to apply insulating concrete to a depth of 8+" over all surfaces. Then, using lath and stucco can enclose the previously exposed 'raw' edge of the insulating hearth when I stucco the entire vertical block surface and oven wall/roof.
Is there crazy thinking going on on my part?

Final question - and yes I prowled the insulation threads - Do any of you really feel strongly enough about the improved insulation between FB's ceramic blanket and insulating concrete to strongly recommend using it? Shipping is exhorbitant but I could pick up one box while in Ca next week and ship it to myself moderately inexpensively and then continue with the concrete mix to finish. Besides, I'd like to support FB for the help they provide.

Thanks all.

Never do once what can be done thrice.

tusr18a 04-27-2011 05:34 PM

Re: Building error...Suggestions?
I help with the second question. Use the ceramic blanket product. Either source through Forno Bravo or look to this local vendor as a possible source for this material. It will likely not be any cheaper. However, you will save the postage.

Tscarborough 04-27-2011 05:48 PM

Re: Building error...Suggestions?
Either way, removing perlcrete is about as difficult as carving a pumpkin.

Tman1 04-27-2011 05:52 PM

Re: Building error...Suggestions?
Pictures man, we need pictures!!

Barstool 04-28-2011 08:13 AM

Re: Building error...Suggestions?
1 Attachment(s)
Not being a great one for picture hands tend to be awfully grubby. I think this illustrates my question somewhat. I suspect I will have a total of 3.2 photos by the time the project is complete (or abandoned).

RTflorida 04-28-2011 11:39 AM

Re: Building error...Suggestions?
The advantage to ceramic fiber blanket and boards is in there insulating properties. 2" blanket on the dome, 2" board under the hearth = 4" of vermiculite or perlite concrete. I would try to source locally, I'm sure that you have a refractory supplier or pottery kiln supplier somewhere close by.


SableSprings 04-28-2011 12:14 PM

Re: Building error...Suggestions?
Your issue with the "extra perlcrete/vermicrete" slab layer is covered pretty well in Cdubs' Casa90 Build thread in the Forum's Getting Started section. (I put a link below to the second page of the discussion where his "problem" and yours coincide.) Take a look at how he ended up cutting some of the extra vermicrete skirt away from the slab to secure his enclosure build. He also has a pretty good series of comments/discussion from other members on the insulating blankets and value of additional cement based insulating cover.

Neil2 04-28-2011 04:53 PM

Re: Building error...Suggestions?
Once your oven dome and insulation is finished, I would cut back the suspended slab insulation layer.

The vermicrete is very porous and you do not want to expose it to moisture.

brickie in oz 04-28-2011 10:18 PM

Re: Building error...Suggestions?

Originally Posted by Barstool (Post 111974)
my hands tend to be awfully grubby.

We dont want pics of your hands. :rolleyes:

My hands are always grubby but I take lots of pics, the boys and girls here need a fix, or is that a pix? :p

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