adobe+vermiculita insulation

[danqui]

what would be a good mixture for the insulation under the ovenfloor, and how thick it should be... adobe with vermiculita??

[dmun]

Re: adobe+vermiculita insulation

You can use your vermiculite to insulate under the oven: a mixture of five to one by volume with portland cement will make vermiculite concrete, which will set up to a cork like consistency in about a week. Four inches is the minimum recommended under floor insulation.

[JoeyVelderrain]

Re: adobe+vermiculita insulation

Four inches is the minimum recommended under floor insulation.

is this also the case under 2.5" thick firebrick floors?

what is the mixing recipe for perlcrete? I'm having trouble finding vermiculite in Louisiana, water retention is not our problem or...rather retaining too much water is a problem for plants here.

[dmun]

Re: adobe+vermiculita insulation

Yep, four inches all around. Perlite works the same as vermiculite, that's what I used. Full instructions here

[ThisOldGarageNJ]

Re: adobe+vermiculita insulation

I'm having trouble finding vermiculite in Louisiana

www.uline.com

They have 4 cubic foot bags about 22 dollars each.. Have you tried a pool supply, they sometimes sell it premixed with the concrete

Mark

[JoeyVelderrain]

Re: adobe+vermiculita insulation

Mark,
I bought some perlite at lowes, before I got your post. I think it will work out ok.
I also picked up a bag of pulverized limestone. The way I understand it, the less portland cement you use the better the perlcrete will work. What about the limestone? What is a good ratio to use?

[ThisOldGarageNJ]

Re: adobe+vermiculita insulation

the way I understand it the more lime you add the stickier it becomes,,, but im hoping someone else can answer this question better...

[kebwi]

Re: adobe+vermiculita insulation

I'm a little confused. Most vermcrete/perlcrete recipes are pure vermiculite/perlite and Portland, but occasionally I see references to mixing in lime.

Why? And how does one decide whether lime is a helpful additive for a particular application?

And is there any utility in using a higher a ratio of 6:1 or 7:1? I realize we may need 5:1 under the floor to achieve structural support, but on top of the dome we need much less support. Would a higher ratio provide better thermal insulation and still be strong enough to hold together?

Would it be advisable (or specifically *in*advisable to include a chicken wire matrix in the perlcrete (like putting standard mesh in standard concrete), especially at higher ratios? Would that help any?

[ThisOldGarageNJ]

Re: adobe+vermiculita insulation

there have been 10-1 mixes I've seen on here, Im pretty sure I used 6-1, I also mixed mine in a mixer as opposed to by hand,,(some dont recommen using a mixer) My point is, I dont see why you would need lime in ther vermicrete, I dont think its necessary.. In the stucco yes, I didnt use stucco I used the quikrete Surface Bonding Cement, or my needs it was easy to work with and adds structural strength to whatever you apply it to as well.. Hope that answers your question

Mark

[JoeyVelderrain]

Re: adobe+vermiculita insulation

there have been 10-1 mixes I've seen on here, Im pretty sure I used 6-1, I also mixed mine in a mixer as opposed to by hand,,(some dont recommen using a mixer) My point is, I dont see why you would need lime in ther vermicrete, I dont think its necessary.. In the stucco yes, I didnt use stucco I used the quikrete Surface Bonding Cement, or my needs it was easy to work with and adds structural strength to whatever you apply it to as well.. Hope that answers your question

Mark

I hope I didn't hijack this thread but...

So use lime on the dome render but not needed on the hearth insulation?

[dmun]

Re: adobe+vermiculita insulation

So use lime on the dome render but not needed on the hearth insulation?

Nope, no lime in vermiculite concrete. The fluffy stuff substitutes for the solid aggregate in regular concrete.

And just as a side note, "render" is UK/Australian talk for stucco. No one will know what you're talking about here if you use that word. They'll think you're talking about purifying animal fats.

[david s]

Re: adobe+vermiculita insulation

For the dome I use a 10:1 vermiculite, cement mix. The less cement you use, the less dense the mixture becomes and consequently the better it will insulate. The trouble is that the cement is what holds it together. A 10:1 mix seems like it"ll never work when you apply it but it hardens up sufficiently to hold in place ok and provides a firm enough surface to stucco (render) onto. Others may disagree but this works for me.

[dmun]

Re: adobe+vermiculita insulation

For the dome I use a 10:1 vermiculite, cement mix.

The higher vermiculite proportion works fine if you premix the water and the portland with an electric drill paddle attachment: this slurry then wets the vermiculite and you get even distribution, which you can't be sure of with dry mixing.

[kebwi]

Re: adobe+vermiculita insulation

When you say it works fine, dmun, do you mean that if you use the described method (drill mix, then add vermiculite last) then up to 10:1 can replace the standard 5:1 even for structural support, like the hearth...or would you not recommend going over 5:1 for the hearth and only using higher ratios for the dome?

[dmun]

Re: adobe+vermiculita insulation

I can't say from personal experience since I used the 5:1 mix dry and add water method.
The leaner mix was developed after I built my oven. I'll let someone else who actually did it answer this question.