Casa90 Build

[SableSprings]

Re: Casa90 Build

I think adding more insulation is always a good idea. So putting in your 3" of vermicrete under the ceramic board will just give you more "lasting power" on your oven's heat retention. Also having the final hearth height at the proper level for you will prove really valuable to your back. I'm just under 6' and my final hearth surface level is at 41". I can't tell you how nice it is to be able to work the oven standing instead of stooping! (I was fortunate to be able to work with an oven that was a bit too low for me before my build...so I really appreciate having a little more hearth height.)

Note that concrete continues to cure and harden for over a week after it is poured. Keeping it moist will actually increase its strength. Most contractors and masonry people I've talked to will keep a new pour moist and covered for at least one week before working on it. The downside of the vermicrete is that you need to give it some extra drying time before the insulation starts to work for you. That means you'll want to put in that insulation, let it cure, and then let it dry before you cover it totally with the rest of the build.

Hope that helps...

[Cdubs]

Re: Casa90 Build

Thanks Mike - your Dragonfly Den looks fantastic!! I just finished pouring the slab and all looks good right now. The one thing that I'm worried about is the stregnth this layer will have. Like many people on this site I have not worked with vermiculite before and am not sure how will it dry.

My main concern is if the vermiculite layer will be strong enough to withstand the weight of my enclosure. I plan on using the metal studs and finishing it with cultured stone. Will a 3 inch vermiculite/cement slab be able hold that up?

[Paul in Rockwall TX]

Re: Casa90 Build

that stuff can be soft. It holds the weight of the oven ok spread out, but I chose not to build the frame on it mainly because I wasn't convincd the anchors woud grab well enough. I left a reveal around the edges for the framing and used tap cons to connect.

PhotoPlog - Hearth and Stand

[SableSprings]

Re: Casa90 Build

As Paul noted, the compression strength on the cured vermicrete is very good and should have no problems supporting the weight of your Casa90 kit. Again as Paul noted, the problem with the vermicrete is that it won't hold bolts (very little lateral strength). If you feel the need to bolt the covering structure's frame down or feel that the weight of the facade will be too much, you might find it useful to dig/cut a trench into the vermicrete around the outside of the actual kit perimeter where your covering structure will sit - kind of a reverse moat. That way you can fill the trench with concrete or tie/bolt directly to the concrete slab for anchoring.

The vermicrete on the edges of your slab will also need to be protected since they won't take much wear & tear. I don't know anything about the attachment of the cultured stone...if it needs a solid bolting for the base, the side edges of the vermicrete that may also be an issue for the cultured stone base. Again, you may need to rethink how you'll need to anchor in that stone base. It may be that the top pieces of the cultured stone will tie in and protect the side pieces over that top 3" with no problems - sorry, but I just don't have a clue about cultured stone work.

I was thinking originally that you'd just be pouring a layer of vermicrete under where the oven kit would sit...not over the entire slab. I guess that's why even with kits & great plans, we all end up with unique builds.

[Cdubs]

Re: Casa90 Build

Paul - Thanks for the link to your photoblog. I wish I would have seen them before I poured the vermicrete slab. You would think that after 6+ months of research I would have come across something on this.

Sablesprings - thanks for the insite. I am a little worried about digging a "moat" and messing up the level slab that I have now. What I didn't metion was that I actually went with a 3.5/1 verm to cement mix. I am hoping that will make it strong enough to drill into. The only reason I did this was because the only store that sold Verm hads 3 bags left. I just hope it will hold the bolts I use to put up my metal studs.

On a better note...look what showed up today!! The third picture shows the two layers - I took off the support frame today.

Another question, when I opened the crate today the blanket was on top. After taking it out to look at the oven my arms became very ichy. Is there something I should know about this stuff?

[Paul in Rockwall TX]

Re: Casa90 Build

the vermicrete is easy to cut. you might be best served by cutting into it 4" around the perimeter and down to the hard hearth. 3-1/2 for the metal stud and 1/2 for the concrete backer, if that's what you're doing. it's a little messy, but can be acomplished pretty quickly.

I had to do the same for an inch up front, but no big deal.

[Paul in Rockwall TX]

Re: Casa90 Build

regarding the blanket, they recommend mask & gloves (neither of which I used, unfortunately). It's ceramic fiber, not too harmfull. I didn't work with it much, just gently cut it with scissors and layered it up. overdid it really, but my oven is cool to the touch outside while 1000 inside.

but it's not worse than fiberglass - it's not asbestos, so no worries.

[Cdubs]

Re: Casa90 Build

Paul - What if I decided not to cut the slaab like you suggest. What do you think would be the best way to attached the metal studs to the Vermicrete?

[Paul in Rockwall TX]

Re: Casa90 Build

in that case, perhaps a long wedge anchor. drill a hole through the vermicrete to the hard concrete. drill a couple of inches into the concrete to set the wedge anchor, using a 7 or 8 inch anchor. then, lay the stud on top of the vermicrete, drill a hole through the metal track and attach it that way, if that makes sense.

maybe a fender washer, but maybe not necessary. just thinking off the top of my head, but I think that would work fine and would torque down tight.

yes - I think so.

[Paul in Rockwall TX]

Re: Casa90 Build

another late thought - a 3/8 anchor would be fine, but you may need to go up to 1/2-13 to get the length needed.

[SableSprings]

Re: Casa90 Build

Good job on the pour(s). The concrete and vermicrete turned out very well. I had started with a perlite:cement mix of 5:1 on the base and used 6:1 on the capping insulation...no problems with compression for me. So your 3.5:1 mix should have much better strength all around. Looking at the pour's cross section, the mix looks good. Great tips from Paul on different methods of anchoring here--if you have problems. I bet this is all going to turn out just dandy and that you won't have any problems here (other than the normal ones).

Remember that although the vermicrete will hold water for a long time, you need to keep the pour moist while it hardens and cures. Covering the top slab(s) with plastic for at least a week is probably all you need to do. And the longer the vermicrete can dry after at least a week of moist curing, the better. However, since you will be using the base insulation pad provided by FB as your primary insulation, you won't need to wait until the vermicrete is completely dry before you start building and using the oven. FYI: I would be surprised if you didn't see steam venting from underneath for a while...no worries as long as you know what it is.

As advised, I'd definitely be wearing a mask & gloves when you work with the ceramic blanket (and it sounds like an old shirt/pants that's going to the dump right after the job is done wouldn't be a bad idea either if you find you're exceptionally sensitive to it). Remember that even though it may not be asbestos, the fibers will be happy to stay in your lungs...not a good thing.

Keep us up on how the oven's coming together.

[david s]

Re: Casa90 Build

"As advised, I'd definitely be wearing a mask & gloves when you work with the ceramic blanket (and it sounds like an old shirt/pants that's going to the dump right after the job is done wouldn't be a bad idea either if you find you're exceptionally sensitive to it). Remember that even though it may not be asbestos, the fibers will be happy to stay in your lungs...not a good thing."


The stuff is classified as a class 2 carcinogen. unable to be even sold in Germany.

Anything richer than 10:1 as an insulating mix over the dome is too much cement IMO. You are actually adding more weight with cement than vermiculite and this simply results in poor insulation. You have to make it stronger under the floor because it has to hold the weight, but on the sides and top of the dome you only need it strong enough to hold together so you can render/stucco over it.

[Cdubs]

Re: Casa90 Build

Paul - thanks for all the great ideas. How many do you think I would need to put in to make the enclosure stable? Also, how deep do you think I need to drill into the concrete slab?

SableSpring - thanks for the nice words. My wife seems pretty impressed that I even knew what concrete was. I kept on telling her that I was handy but too tired to actually do anything myself. This really has been a very rewarding project so far.

David - I didn't realize this stuff was so serious. You would think that there would be more written about it in the forum and on the installation guide. I will def be using a mask and gloves when I finally install it. I'm going to let the verm/cement mix sit for another day and then start the rest of the build.

Thanks for all your help!!

[david s]

Re: Casa90 Build

Cdubs,
I am probably oversensitive re carcinogens. My Dad, being a doctor, did some military service for the Brits when they were testing their nukes in Australia. He only made one visit, I think around 1960, but ended up dying of an unusual cancer in 1984. All the servicemen who served there are now dead, most of cancer. Unfortunately effects of exposure usually don't present themselves for 20 years or so. I try to avoid contact with anything slightly suspicious now.
Dave

[Cdubs]

Re: Casa90 Build

Dave,

I'm so sorry to hear about the loss of your father. Obviously it's almost impossible to link the two but it is absolutely something to look at. If it takes me putting on a mask to protect myself from a potentially harmful substance, then guess what I'm going to buy.