The plan was to use clay, I started using brick today. Paul's 36"er

[Paul150]

Hello, first of all I would like to thank all who commented on my question in the newbie section (90 vs taper). I now have no fear to proceed. A special thanks to texman who encouraged me to post more pics and elaborate.

For me, all the pleasurable things in life seem to take time, effort, dedication, patience, money and a support group (my wife). I make my own sour kraut, maple syrup, jerky, sausage, beer, and have gardens. I hunt, fish, and do what I'm told.

I initially wanted to make the coolest pizza, bread oven at a fairly low cost that would blend in with my patio. I thought a clay, cob, earthen oven was it. I built a base, sand dome (oven ID) then a 3" clay dome. I was planning to add another 7" of insulation when it started to crack, bad. My sand to clay ratio was off. We tore it apart, added more sand to the clay and built another dome. Due to the humidity it crumbled this time. Just as I was ready to cry my support group said, just spend the extra money and build a brick oven.

I am ready to build a brick oven and am glad I have people (friends) to help and support me in time of need. Attached is how I got to where I am today.

I look forward to you questions and comments. Tomorrow I am laying soldiers.

[Paul150]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

FYI - After my 4" concrete pour, I used a clay/sand/straw base (1.5") then a bottle layer (2.5") then a clay/sand/sawdust layer (1") for a total insulation layer of about 5 inches.

[dakzaag]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

There is a video of a cob oven being built. The author gives detail of his mix etc. and you get to see the whole thing. I would look it up, but then you would not have the benefit of learning how to search. Besides you might have the brick already.

For what it is worth, sand and glass are not great insulators. If it is not too late, a really lean mix of Portland and Vermiculite or Perelite or Zonalite makes a fairly cost efficient insulator.

The only advantage of more insulation is decreasing the amount of wood needed to heat the oven to saturation and how long the oven retains heat after the fire goes out. So if you have unlimited supply of wood or just want to cook pizza, your fine. If your thinking about bread two days later, you need better insulation. Or if you have to buy wood, then you definitely want to insulate better.

Third time is a charm, don't stack your joints. One on top of two!

[Paul150]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

I am taking Dakzaag's suggestion and removing the mud and bottles. The soldiers will have to wait.

[Laurentius]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

I am taking Dakzaag's suggestion and removing the mud and bottles. The soldiers will have to wait.

Hi Paul,

That a great decision, remove the bottles and mud, concentrate on insulation(proper insulation of an oven) that the different of having an efficient oven or a heat sink. The credo is "insulate, insulate, insulate"! And you won`t be sorry.

[texman]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

Paul

Glad to see that you are getting some good advice. i really think you will be much happier with a brick oven with good insulation, so you are on the right track. take your tim and enjoy.

Texman

[Paul150]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

Picking up my Vermiculite and protland tomorrow to make some vermicrete (5:1 ver/port) after removing the mud and bottles, I have 4.5 inches to pour. What is the minimum time to wait before I can set my oven floor bricks down on my thin layer of sand/portland?

[Paul150]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

Soooo.... Any ideas? How long do I need to wait after vermicrete?

[dakzaag]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

I have an oven that I fired today for the first time this year. A few places the Vermicrete is poking out from under the stucco, it is still soft and spongy and I built the oven last summer.
Two things to think about. First the mix is a weak mix and takes a loooong time to dry out, so it needs a fence or form around it to remain in place while you are building on top of it. If you don't protect it, you will scrub it off as you lean over to stack brick and any other building activity that takes place above the insulating layer. Some guys form a sink in the base concrete which they then fill up with the vermicrete. Others build a form on top of the base to hold the insulation and leave that in place as long as the build process takes and some never take the form out, just leave it there to be covered with whatever the cover is going to be. I think you have the base done, so it probably makes sense to form up the vermicrete and then wait a couple of days for it to begin to harden. It never really gets solid like concrete, but it will be strong enough to hold up the oven.
Make sure it is a flat as you can possibly get it, because any ripples or high spots will show up on your oven floor. One nice thing about it is you can take high spots down loong after the pour if you find a problem while laying the floor.
Another alternative is a layer of Masonite or Cement board between the vermicrete and the oven floor. This holds up to temperatures well enough and gives you a flat surface to build off of. Some of that stuff has foam beads in it for insulation value under tile floor and I would avoid that product as the beads will surely melt and then the board might compress. If you use cement board, you can build the next day, but remember that moisture has to get out one way or another. If you get a good hot fire going over a wet insulation bed, steam is going to get generated and how the steam comes out is usually through the joints in the floor. A lot of heat means a lot of steam, so that is something to consider.
You're on the right track, just take your time and enjoy the process.

[Paul150]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

Well, between honey do's and rain I experienced some timing delays. Since the last post, I poured a 4" layer of vermicrete. I used 4x1" bricks for a guide. FYI I calculated that I needed about 6 cu ft of vermicrete so I bought 8 cu ft thinking I was covered. 8 cu ft of wet vermiculite shrinks down to about 5.5 cu ft. I was a little short so I filled in the sides with straight mortar. Then covered it with cement board, then a bunch of bricks for weight. After a week and a half of sitting, tonight I made some cuts to start my herringbone pattern and laid out a dry run. I will remove them all and clean all the debris off. Do I need to lay them on the 1:1 sand : portland still or is it OK to just lay them on the cement board? Everything is pretty level. Then so I can start my visual, I laid out the opening bricks, gave myself a 1" reveal and angled the show bricks out another inch.

Comments and suggestions please.....

[david s]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

Unless you are in a real rush to get going on the build, it would be a good idea to remove the board on top of the vermicrete and allow sun and wind to dry it out for two or three weeks. Around 1/3 of the volume of the vermicrete is water and it will take a very long time to dry out by fires if you build over it. It will eventually dry of course, but there will still be water there even when it looks dry.

[Paul150]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

It has been a week and a half since the pour. Half of the cement board is "stuck" and I cannot lift it without breaking it so.... I guess I will continue with the build and plan on a longer break in time.

Comments or suggestions?

[oblertone]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

The main reason for laying the oven floor on a mix of any sort is to achieve a level finish, if you can achieve that by using the cement board alone then I'd carry on without; if not then fine sand alone can help.
One other observation I'd make; have you calculated and reserved enough space on your plinth for the insulation layer on the exterior or your oven dome. A smaller (internal diameter) oven with good insulation will be far more satisfactory that a bigger 'leaky' one.

[DavidApp]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

Hello Paul150

You can also use a mix 50/50 of fine sand and fire clay to help level your oven floor. The mix can be wetted and spread out with a notched float. Like you would lay tile.

David

[Paul150]

Re: The plan was to use clay, I started using brick today. Paul's 36"er

Because I created a pocket of stone and had to partially fill it, it made screeding more difficult. So that is why I took the suggestion to pour my vermicrete, make it as level as I could, then put cement board on top, to make it all level. I assumed that I should put the board on at the time of pour. I guess I could have gotten close, screeded and let the vermicrete cure and dry out then use sand to help level the cement board. I really liked the cement board idea for making all the brick edges as level as possible. So I need that ? inch now so the bottom of the brick is resting on my cut out rock front. Unless there is a better idea, I am going to leave the board and build on versus pulling up $70 worth of cement board and after the vermicrete dries out replacing it with fresh $70 cement board or using ? inch of sand.
Comments or suggestions please.