#11  
Old 09-01-2012, 05:23 PM
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Default Re: vermiculite insulation

It is difficult to say how long you should wait before doing the stucco because the rate at which the stuff dries will vary as my experiment demonstrates. I don't really think that strength is an issue in the vermiculite layer because you only need it strong enough so you can stucco against it, so drying as soon as possible is the way to go IMO and as there is still lots of excess water in the layer it should be plenty to allow the hydration process. I've cracked a couple of outer shells from not drying the vermicrete layer sufficiently, so I'm now more careful to take it slower and longer. When the layer looks dry it will still have quite a lot of moisture in it. Try placing some sheet plastic over the vermicrete when you are firing. You will see condensation on the underside of the plastic if moisture is still present. Unfortunately because the blanket insulates so well, not too much heat gets into the vermicrete layer to assist drying. Just monitor the thing carefully and trust your own judgement. Good luck.
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  #12  
Old 09-01-2012, 06:39 PM
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Default Re: vermiculite insulation

"how long should I let it dry before starting on stucco?"

You want it to cure not dry. Allow seven days and keep the vermicrete well and continuously supplied with water. It needs water to cure.
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  #13  
Old 09-01-2012, 09:01 PM
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Default Re: vermiculite insulation

Whilst it's desirable to make the underfloor slab strong, curing it for a week makes sense, but the vermicrete/perlcrete layer only requires enough strength so you can stucco against it. That is part of the reason we use such a lean brew,we don't need strength. The other reason is of course to make it a more efficient insulator. If you end up adding more water to the layer after it has set, you end up having to remove most of it prior to stucco anyway. Apart from the surface there should be plenty of water retained in the grains of vermiculite/perlite for adequate hydration. (See results of my experiment).
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  #14  
Old 09-07-2012, 10:18 AM
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Default Re: vermiculite insulation

Hi Dave, when you stucco, did you just install over perlit/concrete, or did you prep surace at all? Thanks, Pat
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Old 09-07-2012, 03:22 PM
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Default Re: vermiculite insulation

I would keep all concretes wet for at least a week. Vermiculite / cement is a type of concrete. You may as well get a reasonable amount of available strength from it.

Removing excess water after curing is, in my opinion, not that difficult.
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  #16  
Old 09-07-2012, 03:39 PM
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Default Re: vermiculite insulation

Quote:
Originally Posted by irelande5 View Post
Hi Dave, when you stucco, did you just install over perlit/concrete, or did you prep surace at all? Thanks, Pat
When the stuff sets up it is firm enough to stucco straight on to and being rough is ideal for the stucco to adhere to. The strength is in the outer shell so the vermicrete only needs to be strong enough to stucco against. I make sure the vermicrete is dry, ie curing fires after vermiculite and before stucco. After I do the outer shell which I do in one layer about 15mm thick I then wrap the whole thing in cling wrap for a week to keep moisture in that layer for strength. It works for me, but no doubt there are other ways to do it.

Last edited by david s; 09-07-2012 at 03:42 PM.
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  #17  
Old 09-09-2012, 07:00 AM
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Default Re: vermiculite insulation

Thanks Dave, how many layers of 1" do you apply, just one?
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  #18  
Old 09-09-2012, 03:19 PM
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Default Re: vermiculite insulation

Not sure whether you are asking about the vermicrete layer here or the stucco. I do the vermicrete in layers of about one and a half inches thick, allowing a week to dry for each layer, but I apply the stucco in one layer about 3/4" thick.
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