Starting my build

[almondsurf]

After a lot of delay... I'm on my way.

I posted questions on here about 6 months ago and received a lot of help. Thank you to all!
Our back yard has been one project after another to finish. We should be done with the back yard this weekend so I can focus on the oven. I do work a lot so time is a little limited but I hope not to stretch this project out too long.

I am going to try to take a lot of pics and explain my build process to help anyone who happens along this thread, (most likely to learn from my mistakes) and hopefully receive advice from others who actually know what they are doing.

I have no construction / trade experience what-so-ever, but love to work with hands on projects in my down time, so this oven is going to be one of those... "well, let's just try and hope for the best."

I am planning on doing a casted oven. We'll see if it works.

[almondsurf]

Re: Starting my build

Some pictures of where I am at so far...

[almondsurf]

Re: Starting my build

Continued...

[almondsurf]

Re: Starting my build

Pictures...

[almondsurf]

Re: Starting my build

After having leveled the base out, I found out the hard way... uh, I don't have enough concrete! I had my wife run to the store to buy 3 more bags for me to put into the mix (I used 2 of the bags). I chopped it up again so I could add another batch. BTW, a mixer would have been nice rather than mixing all this in our little wheelbarrow. I think this base took me 12 50lb bags of concrete. Which was 4 mixes (batches) in the wheelbarrow.

[almondsurf]

Re: Starting my build

So, I did this base early in the morning and had to run to work for 5hrs or so. When I came home I noticed some serious cracks. I think this was because of the multiple batches (more or less water maybe?) and the very fast drying time (I live in Southern Utah... the desert). I wasn't able to be home to wet it down and regret not having done this on the weekend when I could monitor it a little more closely.
Does anyone think this will cause any issues with carrying the weight of the oven? I plan on doing a 32" (casted) oven.
I have a brother in the construction trade who says I should be able to use a concrete crack sealer (found at HD or Lowes) and shouldn't have any problems. He doesn't build ovens, so I'm open to anyone's input out there.

Thanks!

[Greenman]

Re: Starting my build

You seem to have the slab well reinforced and the cracks will be mostly cosmetic. It would have made for a stronger slab if it was cured more slowly but a cast oven is not so heavy as a pile of bricks.

Your brother is probably right. You still have an insulation layer, board or vermicrete to go over the slab and your cracks should not be an issue.

Interested to watch where you progress from here, I am sure that it will be fine.

[almondsurf]

Re: Starting my build

Thank you for the advice Geenman. Like you mentioned, I don't think the cracks will even show up because it will all be under the oven. So, maybe I will throw down some sealer and get going on the hearth.

I took a couple more images this morning to give more perspective on the size of the cracks verses the size of the oven base.

To others who are newbies like me... make sure you have enough concrete , a mixer is helpful because of consistency of mix and speed of application, and make sure it doesn't cure too fast if you are in a dry climate.

[almondsurf]

Re: Starting my build

I have taken off the form for the oven base. I figured I would ask the community your thoughts on my design and if I need to modify / change anything. How do my measurements look? I have read quite a few forms on casting the oven, but hope some of you may be able to help me further.

I have attached several pictures of my plan. Please see the pics as a reference. I used tinkercad.com for the mock up. The measurements are in inches.

I plan on using a mixture of vermiculite for my base and exterior insulation. Does anyone have a formula, amounts, and ingredients for a homebrew insulation? I read it is good to use bottles in the hearth insulation; any thoughts on that?

My planned recipe (by volume) for the cast:
1 part cement
6 parts sharp sand
2 parts hydrated lime
1 part fire clay
4% 1" Stainless Steel Needles (Link)
1% polypropylene fibers (one handful for every 50lb / bag of cement) (15-20mm long)

Edit:
I am going to add some things from David S in this post so I don't forget them later (Thanks David):

For every 10 parts vermiculite add about 3 parts water. I mix the cement and vermiculite dry first then add the water. You will lose around 20% in volume when you mix the water in so this needs to be accounted for.

Use 5:1 vermiculite,cement ratio for the underfloor insulation.
Use 10:1 for over the dome.

[almondsurf]

Re: Starting my build

Just pictures, no measurements. (sorry, I don't know why the photos are uploading so small??)

[david s]

Re: Starting my build

I have taken off the form for the oven base. I figured I would ask the community your thoughts on my design and if I need to modify / change anything. How do my measurements look? I have read quite a few forms on casting the oven, but hope some of you may be able to help me further.

I have attached several pictures of my plan. Please see the pics as a reference. I used tinkercad.com for the mock up. The measurements are in inches.

I plan on using a mixture of vermiculite for my base and exterior insulation. Does anyone have a formula, amounts, and ingredients for a homebrew insulation? I read it is good to use bottles in the hearth insulation; any thoughts on that?

My planned recipe for the cast:
1 part cement
6 parts sharp sand
2 parts hydrated lime
1 part fire clay
4% 1" Stainless Steel Needles (Link)
1% polypropylene fibers

Your plan looks ok, but you've left yourself hardly any room for the outer shell.
I don't think you need to go so thick for the flue gallery.
Only use bottles for insulation if you can't afford the vermiculite.
Use 5:1 vermiculite,cement ratio for the underfloor insulation.
Use 10:1 for over the dome.
Search vermicrete on this forum for more info.

[almondsurf]

Re: Starting my build

Thanks David. I did search vermiculite and went through around 15 threads and found some info, but not specific ratio's like you have stated. Thank you, that is going to be a huge help.

Good point on the flue gallery, I will modify that to be 3 inches with the rest of the oven (unless, based on the paragraph below, I should reduce it further to 2 inches).

As for the outer shell, I left 1 inch... and now that I think about it, that is only .5 inches on each side. How thick is the typical outer shell/stucco? Would you recommend taking an inch off the refractory cast layer (I have read that the cast can actually be pretty thin, but insulation needs to be pretty thick) or should I shrink the whole design a little. Admittedly, when building the base, I was planning on constructing a 30" oven but thought I could fit a 32 after the base was done, so ether size is fine for me.

Or, should I just use Super Wool Blanket for the exterior insulation? I read that I only need 2" of that stuff. I was trying to save cost, but I am having a pretty hard time finding vermiculite (other than here which is expensive)so the blanket might be a good option?

[SableSprings]

Re: Starting my build

Or, should I just use Super Wool Blanket for the exterior insulation? I read that I only need 2" of that stuff. I was trying to save cost, but I am having a pretty hard time finding vermiculite (other than here which is expensive)so the blanket might be a good option?

I used perlite instead of vermiculite and found it more readily available in both Landscape/Garden shops and Brick/Concrete supply businesses. My records show I purchased a 4 cubic Ft bag (25#) for a little over $12.50 in 2009. I do remember that you needed to specify the non-silicon treated variety, but the cost compared to perlite or vermiculite at Home Depot & Lowes was far less. I also noticed that the perlite purchased at the Garden shop was slightly larger "grained" than the other bags. Proportions as noted by David for vermiculite work for perlite as well (and these are volume proportions...I just used the bucket method to measure )

In terms of effectiveness and ease of application/use, I highly recommend biting the bullet and using the ceramic board for the base insulation and the ceramic wool blanket type insulation for the dome. I've done both insulation types and would now always choose the commercial ceramic types over the vermiculite/perlite options based on my installation experiences. Although both insulation methods will work well, you definitely will save money with vermiculite/perlite. But when you add in your hands-on efforts (making/removing forms, mixing with cement, curing time, drying time-removing water retained in the perlcrete/vermicrete, etc.) it's not that much of a difference (IMHO).

[almondsurf]

Re: Starting my build

Thank you for the info SableSprings. The info you guys are providing is very helpful. I am currently looking and pricing the FB and blanket. It is hard to come by though. I am trying to find it out of Las Vegas (which is the nearest large city, about 1.5 hrs away). I found the Super Wool Blanket @ Pacific Insulation ~ $60 for 2"x2'x25'. They are supposed to call back on a price for the FB. I guess they even have a hard time getting the Fiber Board in. They had Super Wool Board, but it is $26 per sq ft. for a 2" board, that's $312 for 3x4... Yikes!

[SableSprings]

Re: Starting my build

The Forno Bravo prices are a bit better for the board - 36" x 24" x 2" = $70 ($11.67/sq ft -- it's #IFBBO2436) and 50' of 1" blanket is $75 #IFBBL50 (a bit more than the Pacific material you found). You can get a quote from Forno Bravo and it sounds like it will be worth the effort. Also check around places that install commercial boilers and the like...industrial supply places like that might be able to give you some other sources to check. I have also found "stuff" at places that do demolition work and salvage operations. There are several WFO builds in Utah, search for threads with Utah & insulation sources on the forum...they might name some other suppliers in your area.

Good luck & remember - the material hunt is half the fun!