Terraced enclosure Design Styles, Chimneys and Finish Discuss Terraced enclosure in the Pizza Oven Design and Installation forums; Hmmm, good point of concern jmhep . I had been thinking that a copious layer of surface bonding cement, following ...

[kebwi]

Hmmm, good point of concern jmhep. I had been thinking that a copious layer of surface bonding cement, following by several layers of plastic (weighted down by the dirt) might be sufficient, but perhaps I need other factors as well. Pool Armor was mentioned earlier in this thread. Having not worked with surface bonding cement yet, I'm not sure what its properties are in terms of water absorption.

P.S., I never had any intention of trusting the vermicrete layer to be even the remotest bit water-tight. Remember, my original design was loose vermiculite fill, so, I had been planning on a waterproof shell from the outset.

Thanks.

[Archena]

Originally Posted by kebwi

Help me understand your idea Archena. Are you suggesting a skeletal framework *above* the above, from which terraces are suspended, like a suspension bridge?

No, but I think I know where the confusion comes from - I hadn't thought about what 'stringer' would sound like since my Daddy taught me that stuff as a kid (not that I was actually building things - I was just the really curious kid pestering him with questions).

This is a stringer:


What I'm suggesting is basically a circular staircase that surrounds but does not touch the oven. You can build it out of wood then seal all or part with concrete or build steel containers - whatever. Wood stringers can be bought pre-made at most any home improvement store (the image is from Amazon) or you can make them to whatever size you like since the rise won't matter as much.

Hmm, come to think of it, that would be a pretty cool planter surround for a deck or patio. I may steal the idea if you don't mind?

[kebwi]

Go for it.

[kebwi]

I'll keep this question in this thread since it arised from my various enclosure designs, but it is somewhat of a tangent to the original subject of the thread:

I am trying to determine what I will *lose* by molding the terraces out of vermicrete instead of building an enclosure shell and filling it with vermiculite. In either case, I would apply an outer coating of some sort of stucco (surface bonding cement being the most likely candidate), along with perhaps other surfaces to increase water resistance. That's not my point here though.

What I really want to know is the comparative insulation value (R value?!) of loose vermiculite vs. the common ratios of vermicrete, 5:1 to 12:1, although I admit that for an upper enclosure I would probably do something between 8:1 and 12:1.

Does anyone know how much better loose vermiculite is vs. 8:1 or 12:1 vermicrete? Obviously for a given thickness, that goes without saying.

Thanks.

[Tscarborough]

I have seen that information on this forum...somewhere.

But, there is no way that vermicucrete at anything more than 1-2-3 (P-S-V) ratio could be used for anything structural in a vertical plane.

[kebwi]

Originally Posted by Tscarborough

But, there is no way that vermicucrete at anything more than 1-2-3 (P-S-V) ratio could be used for anything structural in a vertical plane.

1-2-3 (P-S-V)? 1 part Portland, 2 part ?, 3 part Vermiculite? What's S?

Aside from not understanding the ratio phrasing, I'm also confused by the overall statement. People build entire ovens on top of vermicrete slabs at 5:1. The structure I'm trying to build needs to support the pressure (not weight, pressure, I figure, right?) of the surface bonding cement and a few inches of dirt. We know these high ratios will support the SBC because all the igloos on the site demonstrate it. My original concern had been the dirt, which will conceivably be a few hundred pounds, but the more I think about it, the pressure of the dirt will be infinitesimal. A couple inches of dirt weighs practically nothing per-inch. I mean, a little column of dirt with a one-inch foot print doesn't exert much pressure on that foot print when the column is a few inches tall. That's what I'm saying.

Why do you think building the structure out of solid vermicrete won't work? I'm just not understanding your terminology?

[Tscarborough]

Sand. On the hearth, all that matters is compressive strength, which is not a problem. When you use it in a vertical application, shear, flexural, and tensile strength matter. Realistically, you will need 4" of dirt to grow anything. Searching, I get approximately 2.66 pounds per SqFt of hydrostatic pressure for 4", so coated with surface bonding cement you should be good (rated at around 2880PSF in the vertical).

[kebwi]

Originally Posted by Tscarborough

I have seen that information on this forum...somewhere.

I don't mean to be argumentative, but I'm not certain that you have. There are a lot of threads about insulation and vermicrete, and I agree that in casually dwelling on my experiences reading the threads it might seem like my question has been addressed, but I have exhaustively searched the forum for hours, and I honestly don't believe the specific question I asked above has been answered before.

If you really definitely saw this exactly question answered, then I apologize, but I've put in the hours and I just can't find it.

Namely, the comparative insulation value of loose vermiculite, dense vermicrete (5:1) and thin vermicrete (10:1-12:1). The answer doesn't have to be in the form of formal R-values if that data isn't available. Any version of an answer would do, including perhaps approximate equivalency thicknesses, e.g., 1" vermiculite equals X" 5:1 equals Y" 12:1. Something like that would be really helpful information.

If anyone has any information on this at all, I would really appreciate having it in hand as I proceed with my design.

Sorry I'm arguing with you, but I just can't find this information anywhere.

Thank you very much.

[Tscarborough]

I think you are right. It may have been the compressive strength of various ratios that I am thinking about. Let me see what I can find on the web.

[Tscarborough]

Vermiculite Insulating Concrete--The Schundler Company

Thermal conductivity - Wikipedia, the free encyclopedia

There you go.