Forno Bravo Forum: The Wood-Fired Oven Community

Forno Bravo Forum: The Wood-Fired Oven Community (
-   Newbie Forum (
-   -   vermiculite/portland and weather (

jnpe 07-22-2009 11:36 AM

vermiculite/portland and weather
I will be ready to add insulation to my slab in a few days for my WFO here in southwest VA and have a question re. vermiculite/Portland.

Is this mixture weather resistant? I plan to extend the insulation past the edges of the dome but I am concerned about exposure in that area to the elements. Will it wick moisture under the dome and lose insulating value? Should it be waterproofed?


Jed 07-23-2009 11:44 AM

Re: vermiculite/portland and weather
Hey Jnpe,

I can't say I remember any conversation about this question in the past, but here are my two cents on the subject...

The vermiculite / Portland cement mixture is a very porous product. It will absorb water.

It would certainly hold water andwhen it gets wet it will wick the water through the full structure. And if you live where it will freeze, the frozen water will break up the structure created by the Portland cement.

I think if you want your structure to last, you will cover the exposed vermicultie / Portland insulation with tile, or stone or some product that will protect this insulation from the weather and keep it dry.


dmun 07-23-2009 07:23 PM

Re: vermiculite/portland and weather
Those builders who take their vermiculite concrete out to the edge of the support slab usually cover it with whatever surface treatment they use for the stand/structure be it stucco, tile, stone or brick face, etc.

It's not recommended to leave your insulation open to the weather.

jnpe 07-26-2009 05:15 AM

Re: vermiculite/portland and weather
Thanks for the replies!

Most good thermal insulators by design have a high degree of porosity and just wanted to make sure I wasn’t missing something re. verm./port. Encapsulating the exposed edges with stucco sounds like a reasonable approach and planning to proceed that way.

Found one bag of #8 vermiculite locally and have ordered the remainder.

Thanks Again

cvdukes 07-26-2009 03:18 PM

Re: vermiculite/portland and weather
Definitely don't leave the vermiculite mixture exposed to the weather! See my post from last year about failed attempt to use it as a roofing material. It will continue to sorb moisture if not weatherproofed... then it will freeze and chip off in small chunks.

All times are GMT -7. The time now is 05:52 AM.

Powered by vBulletin® Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
© 2006/10 Forno Bravo, LLC