Oven Build in SC

[UtahBeehiver]

Re: Oven Build in SC

OMG, makes my stomach hurt thinking about your THUMB. Way to go getting back on the bike after falling off. Build is looking good. I am sure Lizzie is hoping for pizza scraps. Nice solid framing and forming.

[videts38]

Re: Oven Build in SC

Hallelujah, (if that's how you spell it). Finally finished out the forms and rebar for the hearth pad and did the pour this Labor Day weekend. It feels like it was a long time a coming! Went fairly smooth in all. Started at the back archway and worked our way forward. Unfortunately I did it with buckets!. I was pretty ambitious at first, then as we moved forward those buckets didn't seem as friendly!! Thank God for the help I had. My father-in law Chuck was the mixer, and my buddy Bill did the spreading and screeding with me. Since this is my project I figured it was only right I work the hardest. I loaded the 80 pounders into the mixer then lifted and emptied what seemed like the endless buckets into the forms. Did I mention I can now scratch my knees without bending over!! At least it feels that way. The only part that didn't make me too happy was the Sakrete calculator. For the area and depth I plugged in it said I needed approx-47 80lb bags, well I only need 30 bags, and since it said I needed 47 bags and I had archways to do I picked up 54 bags!! I've never poured concrete before this project so I figured I'd rather be safe and have enough then have to run and get some in the middle of the pour. Needless to say I ended up returning 20 bags and they did have a couple of guys empty the trailer while I was doing the paperwork inside. So all and all it worked out fine.
Any way I'm just happy as can be to be too this point. My plan is for 3 1/2" of vermiculite and cement topped with 2 1/2" insulating firebricks that I have for a total of a 6" thick insulating layer. I plan to put the insulting firebrick in immediately after the vermiculite layer hopefully for a little bonding action. I just have to figure out how to form it. I believe now I'm going for the igloo shape when all done so the insulating layer needs to be round in the form of the oven and large enough for the oven walls to sit on.

Couple questions:
Will the vermiculite/firebrick insulating layer be sufficient enough of an insulating layer?
Does the insulating layer need to extend much beyond the walls any particular amount or just enough to make sure the floor and walls sit upon it? I was just thinking if it would compress or give way if the insulating layer stopped right at the edge of the oven wall.

[dvm]

Re: Oven Build in SC

Videts38

Well Done! The finish on that slab looks like then the work of someone who has done this before.
I don't know about "insulating fire brick". From my reading on the forums the preferred choices for insulation is ceramic fiber board which is an excellent insulator and rated to 2000 F. Two inches of the stuff is equivalent to to many inches of v-crete. I bought mine from Forno Bravo in Marina (it was an easy drive to go pick it up). The sell it on their web site.
I had my insulation extend 2 inches beyond the walls. My walls sit on the insulation, not on the floor.

[dvm]

Re: Oven Build in SC

Example of insulation. I fired my oven last night then closed the door. I am baking bread this morning. The inside is 550, two inches under the floor is 378. The bottom of the floor on top of the insulation is 256. Under the insulation is 90. So more is always better but 2 inches of FB fiber board is very good.

[Pompeii7DC]

Re: Oven Build in SC

Looking great! Congratulations, you should be very proud.

[videts38]

Re: Oven Build in SC

Does anyone have an opinion on how long you need to wait before starting to build on top of the hearth pad after it's been poured? I know I waited a week+ after the foundation slab was poured but I wasn't sure on the hearth pad.

[videts38]

Re: Oven Build in SC

Thanks Pompeii7dc and dvm.
I'm thrilled to get this far and even more excited now that things will get interesting with starting the oven!! I don't think I could have gotten this far or had the confidence to start this project without this forum and its members. The knowledge and experience are the most important tools in the bag!!

[dvm]

Re: Oven Build in SC

Does anyone have an opinion on how long you need to wait before starting to build on top of the hearth pad after it's been poured? I know I waited a week+ after the foundation slab was poured but I wasn't sure on the hearth pad.

Videts38
I would not try to drill any holes in that slab this week but you can certainly start laying down your insulation forms (for v-crete) or cutting ceramic board any time. Are you planning the walls on the floor, or the walls on the insulation?

[videts38]

Re: Oven Build in SC

I'm planning to maintain the igloo shape and not have it enclosed. And from what I've been reading in this forum it suggests to have the floor inside the wall if your keeping the igloo shape. Maybe because of thermal expansion? I'm not quite sure of the correct reason. In that case I'm trying to figure out how to do a circular form for the v/crete portion. I was going to experiment and make a v/crete form up and see if it was possible to cut into it after it has set up because if I can do that then I would just create a square form to the size I need then trace out the circular part of the form and cut away.

Anyone have thoughts of this?

[texman]

Re: Oven Build in SC

You can make a circular form from pressboard (pegboard without holes) and many other thin sheet materials that are flexible. Just rip the sheet to your desired height and calculate the necessary length based on your chosen diameter of your wfo to the outside surface of the walls. So a 36" oven (internal) plus standard brick of 4.5" x 2 sides = 45" diameter Use pi x dia = circumference. in this example, 141.4" circumference. most sheets are 8' length, so rip two and overlap to get the desired circle. you can attach the two with screws facing toward the outside.

I wouldn't try to cut the vermicrete. It is very crumbly and i think you would have a mess. I would do the circle form and add a section for your entry like the FB plans show. After you have poured the vcrete, i would go back with a mortar/sand/fireclay mix and slather around the exposed edge to control the crumble. HTH

The floor inside the dome allows for separate expansion/contraction of the dome and floor. be sure and leave an 1/8" gap between the dome wall and floor.
Look at Gulf's post #66 on your thread. He has a good pic of the form for the vcrete.
Texman

[videts38]

Re: Oven Build in SC

Thanks Texman on your advice. I will go for the flexable masonite board (peg board minus the holes) and create a circular form for the v/crete. And I like the idea of the mortar/sand/fireclay for the edge of the v/crete layer to give a little added strength to the edge seeing how I'll probably be nicking it up a little when I’m standing all over the hearth pad area.
I traced out the ID of the oven form template last night. It feels good now to have moved on from the stand portion temporarily. Every time I asked my wife to take a look she was always saying “It doesn’t look much different than the last time I saw it.” She doesn’t notice all the little things that need to be done to get from point A to point B. Maybe the next time she tell me “It look’s like your making progress. (LOL)

Just took a look at Gulfs pic that you attached and that is exactly what I'm trying to do. That's the nice thing about this forum, anything you try to do has already be tried and tested by someone, somewhere.

Excellent, thanks for the help.

[videts38]

Re: Oven Build in SC

Insulation layer under floor question.
I'm putting 4" of vermiculite/portland mixture under the floor at a 5:1 ratio. I can't remember and can't find if you need to keep this layer wet for a few days after pouring to help it "cure" or if you just let it dry out on it's own. If anybody has some advise I would appreciate it.

[Gulf]

Re: Oven Build in SC

I would not keep it wet, if that means spaying it down with a mist each day. I would keep it covered with some plastic for about a week, though. After that you could just keep it shaded from the sun for another week or two. 28 days is the max for curing portland. I dont think it will get any stronger after that if it is kept wet. Natural aging of concrete, after 28 days of curing, will increase in strength for about 50 years. I would hope that the portland in vcrete responds the same as portland in concrete. I continued keeping my vcrete wet by shading it with firebrick after about two weeks. I will probably pay for that when I do my curing fires .
One thing that I think that you should do, if at all possible, is to keep your forms up for as long as possible. Vcrete will chip on the corners no matter how long you cure it. Building the dome and entry can take a toll the edges of vcrete.

[videts38]

Re: Oven Build in SC

Thanks for the insight Gulf. I will keep it plastic wrapped for a week before building upon it.I planned on keeping the forms around it for as long as possible. Also Texman suggested to "slather" a mortar/sand/fireclay mixture to the edge to keep the edge from crumbling and added strength This made some good sense to me considering previous posts of the weakness of the v/crete edge.
Again, thanks for the input and advise. Onward!!!

[texman]

Re: Oven Build in SC

correction: i used portland/sand/fireclay to firm up the edges. Mortar would work too, i think. I told you wrong, sorry about that. I just added the fireclay to prevent heat breakdown, but if you are using FB board or something like it, the heat on the vcrete wont be a concern.
Keep up the good work.
tracy