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-   -   vermiculite insulation (http://www.fornobravo.com/forum/f8/vermiculite-insulation-18275.html)

irelande5 08-26-2012 02:04 PM

vermiculite insulation
 
Hi all,

Having a hard time locating vermic locally, I did find some at Menards but it is the consistency of sawdust is this okay to use or should it be the size of peanuts thanks Patrick

Gulf 08-26-2012 02:20 PM

Re: vermiculite insulation
 
Have you tried any of your local plant nurseries. Many carry it in medium to course grade in usually 4 cubic feet bags.

Neil2 08-27-2012 11:46 AM

Re: vermiculite insulation
 
"but it is the consistency of sawdust"

You want something coarser than that. As Gulf suggest, try your local nurseries or lanscapers. Coarse grain pearlite will work as well.

irelande5 08-27-2012 01:16 PM

Re: vermiculite insulation
 
Thanks gents good call, just got back from nursery supply house, got 3 bags of course perlite, what kind of consistentcy do I need, thick or thin. Believe its 5 to 1, just don't know how much water to add, thanks again

Neil2 08-27-2012 04:39 PM

Re: vermiculite insulation
 
5:1 for under the oven. 12:1 for dome insulation.

Mix gently by hand, adding only enough water for workability. If water is running out and collecting in the bottom of your wheelbarrow than that is too much. Otherwise the water content is not too critical.

Once poured, keep the mix well supplied with water for at least 7 days and keep it covered with poly to hold the moisture in. You can start laying the floor as early as the next day.

irelande5 08-27-2012 05:06 PM

Re: vermiculite insulation
 
Thx Neil, this is for the oven top, already have the board for underneath, its 12 to 1 for top? I am also using 3 layers of blanket, probably over kill. Thanks again

david s 08-29-2012 02:06 AM

Re: vermiculite insulation
 
1 Attachment(s)
Be sure to allow the vermiculite to dry well before covering over it with stucco to prevent excess steam pressure build up cracking your outer shell.
Check my experiment on drying vermiculite slab attached.It illustrates how much water needs to be eliminated. You can do it all with fire but I find it easier to allow the sun and wind do most of the work. If done in one inch layers you can let each layer dry before proceeding to the next.
With three layers of blanket your vermiculite layer is really only needed to get the shape back, over all those folds and bumps, to a nice hemisphere so you can stucco over it neatly. I use 10:1 which makes it slightly more manageable to apply.

Neil2 08-29-2012 04:05 PM

Re: vermiculite insulation
 
"its 12 to 1 for top?"

Yes. That is what I used.

david s 08-29-2012 06:38 PM

Re: vermiculite insulation
 
Quote:

Originally Posted by irelande5 (Post 137363)
Thanks gents good call, just got back from nursery supply house, got 3 bags of course perlite, what kind of consistentcy do I need, thick or thin. Believe its 5 to 1, just don't know how much water to add, thanks again

For every 10 parts vermiculite you need about 3 parts water, but if the vermiculite is fine it needs about 4 parts water. I guess every vermiculite batch is a bit different and the amount of water it contains would vary from the weather. Use the water left in the bottom of the bucket or barrow method. You can always just adjust it by adding a little more dry material.I don't know quite why, but I find a 50/50 mix of vermiculite and perlite makes a far more workable mix than either of them alone.

irelande5 09-01-2012 05:05 PM

Re: vermiculite insulation
 
Thanks David/Neil,

Just finished installing blanket and topping with perlite mixture, that was a messy job, there were areas I couldnt get it to stick well, mostly on the sides near the middle, but got good coverage on top. Just curious, how long should I let it dry before starting on stucco? How many fires and how hot/long would you recommend to help drive out the moisture/steam? I have done the 5 curing fires, though the last one I didnt let it get above 650f, want to go up to max heat slow as possible. Thanks again for all your help.

Nice work on documentation of you slab David!


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