Vermiculite-concrete as roof

[cvdukes]

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]

Re: Vermiculite-concrete as roof

CV,

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.

Jim

[jeff]

Re: Vermiculite-concrete as roof

Onya CVD. A lot of us are too proud to publish our stuff-ups.
teach.

[Xabia Jim]

Re: Vermiculite-concrete as roof

What about a slate or tile roof over that surface?

[cvdukes]

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]

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]

Re: Vermiculite-concrete as roof

CV,

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.

Les...

[Xabia Jim]

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]

Re: Vermiculite-concrete as roof

XJim,
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]

Re: Vermiculite-concrete as roof

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.

[CanuckJim]

Re: Vermiculite-concrete as roof

CV,

Type S is a cement. Comes in a bag, just like Portland, and it's marked as such. Ditto Type N, which is used for exterior vertical applications because of it's better stickiness. On the hardness scale, Portland is at the top. The other two have more flex. Type S mixed with fine sand (1:3) is standard here for laying block and brick. No reason at all you couldn't use it in your vermic/cement mix.

Jim

[david s]

Re: Vermiculite-concrete as roof

CVDukes, If you use colouring in your portland cement mixture (we call it oxide colouring here in Aust. ) you will not get a particularly good colour because the grey of the cement tends to kill the colour of the oxide. I find it better to make a "paint " from white portland cement (expensive but you don't need much) lime, finest sand you can find. Mix these in equal parts with some oxide and paint it over your cement render. You get a nice colour intensity. Remember to add the same proportions of oxide if you do subsequent coats.

[Frances]

Re: Vermiculite-concrete as roof

uh Jeff... what is that picture of your oven doing hiding in this thread???

Give it its own thread mate, and get the advice it deserves!

I'll start off here, because I happen rather to like those swirls. One piece of advice would be to tone down the light/dark contrast a bit. Say if you went over the whole oven with a translucent layer of ochre. Or put medium ochre/brown brush strokes along the edges of the white swirls, to soften them a bit.

Actually, I'll tell you what I'd probably do: add more little swirls on the big ones. Hang on I'll grab a piece of paper and try to show you what I mean. (Watch this space.)

I think the overall design works beautifully, looks really striking on the small picture, but when its enlarged - well, I see what you mean, it does need a little bit more work

At least, thats my opinion....

[chuckster]

Re: Vermiculite-concrete as roof

I bought powdered dye at Lowes 2 years ago when I built my oven. I used 1/2 of the bag (it came in a box on the outside) to 1 mixer of concrete. It worked OK for the work area next to the oven. It was about $5US if I remember correctly. Its still red two years later.
Chuck

[Dutchoven]

Re: Vermiculite-concrete as roof

Here in the US also...type S is preferrable for load bearing applications...type N(having more lime) is preferred for vertical applications...repointing, covering, surface bonding
Dutch

CV,

Type S is a cement. Comes in a bag, just like Portland, and it's marked as such. Ditto Type N, which is used for exterior vertical applications because of it's better stickiness. On the hardness scale, Portland is at the top. The other two have more flex. Type S mixed with fine sand (1:3) is standard here for laying block and brick. No reason at all you couldn't use it in your vermic/cement mix.

Jim