Starting my build

[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

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.

[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

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!

[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

Pictures...

[almondsurf]

Re: Starting my build

Continued...

[almondsurf]

Re: Starting my build

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

[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.