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cvdukes 03-24-2008 04:27 PM

Vermiculite-concrete as roof
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Back in December when I finished the pizza oven, I made vermiculite-concrete (vermicrete?) to use as the final roof covering. I had come into a large amount of vermiculate straight from the mine at wholesale price, so vermicrete was the cheap way for me to go, plus it gave me some flexibility on the design (pic. 1).
Vermicrete was made of mix of 8 parts vermiculite to 1 part portland. Roof was done in a couple of hours and hardened up sufficiently in a few hours. We had a warm spell in December, so I didn't have to worry about it freezing before it fully set.
Now, 4 months later, can reccomend NOT following my example. We've had widely flucuating temps the past couple of months... a few 80s see-sawing down to the low teens... sometimes as much as 35-40 degrees in just 24 hours. Coupled with enough rain to fool me into believing our drought is ending.
What happens with the vermicrete is that it still soaks up a lot of moisture, then when the temps drop, little parts freeze up and flake off (PIC.2&3). The counter below the roof slope looks a small pile of grey snow from build-up of vermicrete runoff.
Weighing my options on the solution as eventually it'll all flake away. Gave some thought to gluing asphalt shingles down over the vermicrete, but now leaning toward just a covering of ferro-concrete. It'll be easy to cover with a couple layers of chicken wire and just mortar over the top.
Anybody ever use any powdered concrete dyes? Thinking that if I do the ferro-cement covering, I could use a dark dye and make it look like a massive piece if slate

CanuckJim 03-24-2008 06:06 PM

Re: Vermiculite-concrete as roof

You might want to go with a resin mix of stucco basecoat. That will solidify everything. After that, you could apply an exterior stucco coat that will shed water rather nicely. Vermic/Portland is a lesser choice to vermic/Type S or vermic/Type N for outdoors. Both shed water better; not as hard.


jeff 03-25-2008 05:50 AM

Re: Vermiculite-concrete as roof
Onya CVD. A lot of us are too proud to publish our stuff-ups.

Xabia Jim 03-25-2008 07:18 AM

Re: Vermiculite-concrete as roof
What about a slate or tile roof over that surface?

cvdukes 03-25-2008 09:33 PM

Re: Vermiculite-concrete as roof
Canuck Jim:
Used portland type I-II.
I'm confused about Type S portland with Vermiculite. Thought Type S refers to a concrete mix with sand and extra lime added. So how does that work with adding to vermiculite? And Type N?

Xabia Jim: While I agree slate or tile would be a great look, I'm afraid the expense and hassle would probably end up costing more than my entire project...thats why I'm leaning towards a ferro-cement layer, besides I want an excuse to play with some concrete dyes.

Went looking at the big box home improvement store tonight for the powdered concrete dyes...they don't carry it. Just have the liquid dyes that color the entire batch a boring uniform color. I'll have to look around a little more. Still think that if can find some dye powders, I can duplicate the look of big slate peice.

gjbingham 03-25-2008 09:52 PM

Re: Vermiculite-concrete as roof
I found the powdered dye at my local masonry supply store. This town has nothing, but it does have one masonry supply store. I'd suggest you look in the phone book for masonry supplies and give them a call.

Les 03-25-2008 10:09 PM

Re: Vermiculite-concrete as roof

In regard to the Portland, type S is the norm. To my understanding, type N is harder when cured - go with the S, you're not looking for strength. When it comes to freezing temps and reliability, I've used a latex additive that the big box stores do carry; just use it instead of water, it does work. About the dye, can't help you there my friend.


Xabia Jim 03-25-2008 11:18 PM

Re: Vermiculite-concrete as roof
CV...coupla thoughtsa

I found a pile of slate at a dump....wonder if there is any used stuff around...maybe a roofer who has replaced a slate roof?

I've also seen a wash done on cement. The first layer was put down with one color and the second was washed over it to give it a two tone look. It's actually a stamped concrete but could give a nice finish.

good luck....

jeff 03-25-2008 11:34 PM

Re: Vermiculite-concrete as roof
That wash treatment sounds like what I've been toying with. Unfortunately I'm not artistic. Bought the powders today, so will see what happens tomorrow. I guess it's only money,eh.

jeff 03-26-2008 02:04 AM

Re: Vermiculite-concrete as roof
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Classic Grecian design, by crikey.
(I did warn that I wasn't artistic. Strewth, what a retard!)

Any advice short of aborting the entire project could be highly valued, eh.
Yours in (not much) hope,
Jeff the Philistine.

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