Hello. My name is Fabio in it's been a wile since I have gotten on hte forum, due to work related injuries. I am in the final stages of actually constructing the oven. Work stopped some time ago but very soon finish the actual construction of the oven. I have some questions for anyone that can help me with some technical info.
I am building a 42" Tuscan oven, which is under a roof of a outdoor kitchen. The kitchen /patio is shaped in the form of "L" with the oven closing the upper portion of the "L" @ an angle. I have a 12' rounded end bartop with 18'x16' of counter top space, sink, fridge, and wood burning BBQ pit. Electrical run with lights etc. I will be posting some pictures soon , from biginning to what has been done so far. I live in SoCal and the hearth is completed but when the top slab of the hearth was poured I did not insulate it as someone had suggested. So now these are some of the questions that I have.
I have a 10" tile saw that I purchased for some tile work, and was wondering if it is worth cutting each brick to fit tight against each other, or just do it th e way most people have done itwith mortar in between bricks. If it is better to cut the bricks, does anyone have the correct angle of the cuts. I do not remember who posted some drawings that appeared to have been done with a cad program and showed each layer and how it was constructed, but that is what I want to do.
1. Can I still pour let say an 1, 1-1/2" on top of the hearth before laying the main firebricks base first, or is it necessary.
2. In some past pictures I have noticed some one had the main soldier bricks standing straight up and some were cut in half. Which is correct.
3. Once the layers of the walls have been constructed, and sealed do I need to insulate in between the oven and outer section with foil or fire blanket for added insulation or can I just pour about an 1" 0r 1-1/2" of fireclay mortar on top of the oven for mass.
4. What is the correct mixture of fireclay, sand, and cement. I'll be using shovel for measuring or should I be dead on with mixture.
5. Does anyone know where I can purchase a thermometer for this oven, since it will get hot, and a regular thermometer will not work!
6. I will be using sheet metal double insulated flute from Home Depot any suggestions. Is it OK to use this type, since i am going through the roof. By the way the flute will have an slight "S" type bent, not so quite as sharp with the bends, will this hamper the amount of exaust.
7. Do I need a thermal slab before I lay the main bricks. I will be using the yellow firebricks, which I had the supplier call the manufacture to get the right amount of temperature these bricks can handle. They said 1,800 degrees, and the red bricks can handle 2,300 degrees.
Thank you in advance for any help with this info, I am sure I am forgetting something but if I do I'll ask againg.
P.S. Some of the info I had checked out was from dmun, paulages,and ColonelCorn76. :(
I'm not an expert but I am learning as I go as most of the builderrs have. I'll share any information that I can. I have a 10" saw also but probably won't cut many special angle cuts until the top starts closing in. I remember somebody talking about CAD programs for this sort of thing but there is such a large body of information on this forum now that it takes a while to sift through it all.
1. Re: insulating hearth, the original information suggested pouring them on the same day so the layers would adhere together. You might consider dowling the layers by drilling slightly into the original layer and having a very short piece of rebar stick up into the new insulating layer. jengineer has been very helpful in coming up with the correct way to solve problems like this. My insulating layer is on top, poured the same day, and is 4" thick.
2. There is some difference of opinion as to whether a foil layer on the outer edge is helpful or needed. Marcel makes a very good point about the need for it and I think it was Alf that said it probably doesn't help. I plan to use a ceramic blanket over the top after I put 1/2" or so of mortar over the dome. My oven is going to be in a mini building so I'll probably fill around the dome with vermiculite or perlite. If you're going to do an igloo style finish you'll have another way of getting that extra insulation. Maybe putting chicken wire over the dome and applying a 3"-4" layer of perlcrete before the stucco.
3. If you go to the Pompei building directions you can find the formula that James and Jim liked for making the mortar.
That's about all the information I can give. As I said, I'm fumbling my way along. I have a few opinions about things but a lot of them are merely stolen from the builders before me. Good luck. Post some pictures when you can.
Thanks Mike for the info, I think i might have the info on the mixture parts.
As far as insulation I am not sure I will need a 5" of insulation slab, that sound pretty thick considering that firabricks can withstand 1,800 degrees, but I'll take that into consideration.
Ciao Fabio. :)
Fire brick - insulation
The firebrick and the insulation do two different things. The firebrick heats up and reflects the heat from the fire onto the cooking. The insulation keeps the heat in the oven, and makes a BIG difference in how fast, and economically, the oven heats up to cooking temperatures. If the fire brick oven is just sitting there uninsulated your fire is going to be heating the underlying masonry, and the air around the oven, instead of being concentrated inward toward the food. If you get into retained heat cooking, for baking bread and roasts, an uninsulated oven will loose so much heat, so fast that it won't bake.
So in brief, insulation:
Makes for a fast heat up
Higher temperatures for pizza cooking
Economical wood use
Retains heat for oven cooking.
I think the consensus is that insulation is like what the Dutchess of Windsor said about being thin and rich, you can't have too much.
That's good info from dmun about the difference in insulation and thermal mass. I just remembered this morning about a new insulation board that James is now selling. This stuff is an inch or two thick and it sounds like you just put in down on the concrete hearth and it does all the insulating work. James may not be in town now. I notice he's been "silent" lately. You could look through the recent archives and check out the insulating board threads. Knowing what I know now I'd probably opt for that rather than spending an afternoon mixing perlite and portlan cement.
Thanks for posting your questions in the Forum. I think it is helpful for everyone to share experiences. I am pasting your questions, and my shot at some answers here:
Q1. Can I still pour let say an 1, 1-1/2" on top of the hearth before laying the main firebricks base first, or is it necessary.
You need to put an insulating layer below the cooking floor -- 4" vermiculite concrete or 2" of Super Isol will do it. If you put the cooking floor straight on a 6" concrete pad, the heat will move through the whole concrete layer and wick out the bottom. I have seem it happen, and your oven won't cook as well that way. The bottom of the concrete will get really hot.
Q2. In some past pictures I have noticed some one had the main soldier bricks standing straight up and some were cut in half. Which is correct.
You can do it either way and be right. I've seen both style oven produced by professionals, so pick the style that works for you. If you want a higher and straighter wall, us a full-size upright brick -- though it might be more difficult to set the more pronounced curve of the dome; or use a brick cut in half as the upright for a more gentle dome angle.
Q3. Once the layers of the walls have been constructed, and sealed do I need to insulate in between the oven and outer section with foil or fire blanket for added insulation or can I just pour about an 1" 0r 1-1/2" of fireclay mortar on top of the oven for mass.
I would use just enough mortar to lightly coat the oven (for structure integrity). You don't need the extra mass -- as your brick oven will be as thick as a commerical Italian pizzeria at that point. From there out, you only need insulation. Insulfrax is great stuff, then vermiculite or perlite.
Q4. What is the correct mixture of fireclay, sand, and cement. I'll be using shovel for measuring or should I be dead on with mixture.
The basic recipe by volume (shovel or bucket-fulls) is:
1 part portland cement
3 parts sand
1 part fireclay
1 part lime
Builders modify this slightly to get a texture they like, but that is basically it.
Q5. Does anyone know where I can purchase a thermometer for this oven, since it will get hot, and a regular thermometer will not work!
We sell one. :D The Forno Bravo Store has all the installation accessories -- Refrax, Insulfrax, Super Isol, Vermiculite, DuraTech chimney, etc., plus cooking accessories -- thermometer, pizza peels, grills, terracotta, etc. The thermometer is accurate to 932F.
Q6. I will be using sheet metal double insulated flute from Home Depot any suggestions. Is it OK to use this type, since i am going through the roof. By the way the flute will have an slight "S" type bent, not so quite as sharp with the bends, will this hamper the amount of exaust.
I'm not sure HD sells double wall insulated pipe for wood-fired appliances. It used to be called Class A, and is now called UL103(HT). It is different that the pipe used with gas fireplaces. The DuraTech pipe has a 30 degree angle for making your "S". Given that you are running this through your walls, I would get some professional advice from a local HVAC guy.
Q7. Do I need a thermal slab before I lay the main bricks. I will be using the yellow firebricks, which I had the supplier call the manufacture to get the right amount of temperature these bricks can handle. They said 1,800 degrees, and the red bricks can handle 2,300 degrees.
I touched on that above. You need insulation under the cooking floor to keep your heat inside the oven. It isn't how much heat the bricks will withstand, but rather that they are conducting heat straight down into your hearth -- and you need to stop it.
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