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Chuck Eblacker 08-20-2009 08:11 PM

Natural Corbel Stone Dome on Casa 110
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We have just completed the insulating layer of vermiculite concrete on a casa 110 oven. As you can see I am coming up and over with natural stone. Question, if I put an additional 2 inch shell of portland sand over the 4' portland vermiculite, can then adhere my stone directly to the shell of the dome. I was told by the sales people (who should take a course on oven construction) that I need have a supportive structure over the dome to be able to dome over with stone. With this method, the stone is actually supporting itself as it corbels over the top, so the weight is distributed to the sides. Also, with this in mind, should I just veneer up and leave a gap to fill with loose vermiculite? Thanks to anyone who can help me with this.

Ken524 08-21-2009 09:46 AM

Re: Natural Corbel Stone Dome on Casa 110

Your questions are beyond my expertise, but your oven is going to be gorgeous! Someone will jump in with advice.

Welcome to the forum!

pacoast 08-21-2009 11:39 PM

Re: Natural Corbel Stone Dome on Casa 110
Gorgeous stone work, please post more pictures as you go along. I don't see why you would need a support structure for the stone. Most of the weight should transfer vertically down through the stonework. Depending on how you finish it, there may be some sideward thrust, but the mortar should easily account for that. If you are confident that the mortared stonework would stand by itself as a hollow shell, then it is indeed a self-supporting corbel.

Whether you finish it as a veneer or not is really a personal preference. If your oven has enough insulation already, then I'd prefer to mortar to the shell to provide extra safety margin against uncommon loading e.g. wind, accidental impacts, mortar defects, earthquakes, tornadoes, etc. But if you want to have another layer of vermiculite, go ahead.


CanuckJim 08-22-2009 06:49 AM

Re: Natural Corbel Stone Dome on Casa 110

If you're confident with your stone work, it's probable that you don't need a support structure. If you decide to go that route, though, I would not use Portland/sand. Even for laying the stone as a corbel, I'd use Type N and sand, because it's stickier, not as rigid and stands up to water run off.


wood-fired 08-25-2009 08:07 AM

Re: Natural Corbel Stone Dome on Casa 110
as the others say, carry on corbeling over the dome as the weight is distributed to the base. If you've 4" of vermiculite that's absolutely plenty to keep the heat in. I'm not a great fan of Portland cement for stone work unless you mix Hydrated lime into the mortar or use just a NHL 3.5 Hydraulic Lime/ 0-4mm sand mix at 1 part lime to 2-3 sand. Its a much more forgiving mix and not as brittle as Portland.
Its looking good!


Chuck Eblacker 08-25-2009 06:53 PM

Re: Natural Corbel Stone Dome on Casa 110
Thank you to everyone who has replied to my questions. Just to clarify...I never had any intention of using portland for the stonework , my plan all along is to use type S, I was asking if I put a shell of portland mix over the 4"vermiculite insulation, would that be a good way to allow myself to veneer right to the shell?

wood-fired 08-26-2009 02:32 AM

Re: Natural Corbel Stone Dome on Casa 110
chuck, I don't think you need a separate layer as such, just backfill with mix as you corbel over unless your stone is very variable in thickness and your insulating mix is very uneven but it doesn't look like either is the case. If you've put a foil layer over the dome before insulating then that will act as an expansion joint so the layers subsequent should all be stable and independent of the dome movement. There's no fixed answer to these things so carry on and see what happens. I suppose you've just got to make sure the thing is water tight.

Mudologist 10-03-2009 08:54 AM

Re: Natural Corbel Stone Dome on Casa 110
This idea may be to late in coming, but what about a waterproof stucco coating under the stonework?

wood-fired 10-05-2009 01:44 PM

Re: Natural Corbel Stone Dome on Casa 110
I don't really know how you've finished things so far but I should think that if you make sure the stone joints are well filled and brushed off at the end of your work session, I doubt very much you'll get any rain penetration. If its going to worry you sick, stucco over before you start the stonework but I only say that because worry is the one thing you should avoid at all costs when doing anything new! In fact my life motto is " when you start worrying, you stop living".........

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