Starting new build in Dallas

[Dwatkins]

I had one previous question but other than that new to the site. This build started out as a suggestion one evening as my wife and I were sitting out under the pergola and she thought we needed a counter top pizza oven that she saw in an ad. We would usually put the pizza stone in the oven or on the outside Blaze grill, simple enough. But no, I started searching pictures, ideas, and then drawing up some plans which evolved from a simple counter top oven to a 66" round slab, 45" interior oven, bricking the exterior to match the house, extending the pergola, and adding seating around the new oven. ??? What is wrong with people like us? How does it go from a couple hundred dollar suggestion to full blown thousands of dollars and months of work project? Am I alone here? Do other people suffer from this insanity? Well the pics that I have loaded start out with placing the new oven just off the pergola where the round table is next to the fence. I drew off on a 4 x 8 x 1/4 ply to make sure the dimensions were good and then dug it out and started the forms. To make sure the round slab actually came out round I found the center and made a kind of "Indispensable tool". I ripped down another sheet of 1/4" ply to bend for the forms and then ripped down a sheet of 1/8" Masonite to go inside so it would release from the concrete. Placed the rebar, picked up 45 50lbs bags of Quikrete, got out my $220 handy dandy Harbor Freight mixer and one hour and 35 minutes later, slab poured.

[Dwatkins]

Another question I have and would very much appreciate some feedback. I am trying to plan the oven floor height above the slab and I have seen posts that state 2" of Insul board and thought I saw one for 4". I am planning at least pouring a 4" maybe 5" floor and then thinking 2" of insul board on that. Then a layer of 1 1/4' firebrick with another layer for the actual oven floor with standard 2 1/2" fire brick. So two layers of fire brick. My reasoning is to get better insulation on the floor without the high expense of a second layer of Insul board. Any thoughts?

[mongota]

Another question I have and would very much appreciate some feedback. I am trying to plan the oven floor height above the slab and I have seen posts that state 2" of Insul board and thought I saw one for 4". I am planning at least pouring a 4" maybe 5" floor and then thinking 2" of insul board on that. Then a layer of 1 1/4' firebrick with another layer for the actual oven floor with standard 2 1/2" fire brick. So two layers of fire brick. My reasoning is to get better insulation on the floor without the high expense of a second layer of Insul board. Any thoughts?

My opinion?

If your goal is "more insulation" without added expense, adding the layer of split firebricks to the floor, which will give you a total floor brick thickness of 3-3/4" instead of 2-1/2", is counterproductive. The addition of the splits will simply give more floor mass that you have to heat up before achieving desired oven cooking temps.

Having that added thermal mass can somewhat slow the overall temperature drop in the oven...but the trade-off is a longer dome heating time before you ever start to cook. If you're looking to achieve high cooking temps in a fairly reasonable time frame to do pizza, etc, then I'd recommend not adding the second layer of floor brick. If however your goal was to bake batch after batch of bread, then the added floor mass could be worth it.

I have 4" of board insulation under my floor and 4" of blanket over the dome. If I was limited to using just 2" of insulating board under the floor brick, I probably would have considered adding a vermicrete-type of insulating slab under the 2" of board insulation. Or I would have just used 2" of insulboard over a regular slab.

These projects can suffer from price creep. But compare the price of another two inches of board insulation to the overall cost of the oven build. Is it a 5% increase in the overall cost of the build? Or a 15% increase?

Some of the expenses of the build can be put off and completed later on when finances permit. But insulation under the dome? You have to get that right at the beginning of the build. Choose wisely.

With all that written? Two inches of board insulation is better than no insulation. If that's what you end up with, that's what you end up with. And for "short-term" cooking...cooking for several hours on a Friday night, maybe cooking a Saturday morning frittata, with no intentions of cooking Saturday night or Sunday based off of that single Friday night fire? Two inches will do you fine.

[Dwatkins]

Mongo,

Thanks for the reply and it makes perfect since. I will go back to my original plan of 4" of insul board.

DW

[UtahBeehiver]

Agree with Mongo that addition of splits is NOT an additional insulation solution but increases thermal mass. 4" of CaSi an effective thickness under the floor. If you did not put a weep hole in the concrete hearth then now is the time to drill one or two in while the concrete is green. Wet CaSi board is one of the major reasons ovens do not perform well. Water will find its way in from the hearth, chimney or entry floor so raising CaSi off the floor and weep holes are preventative measures.

What is going to be your dome layer configuration? 45" ID plus 2 x 4.5" brick walls, plus 2X3" CaSi blanket, 2 X 1" to 2" stucco or vcrete layer plus outer decorative shell TBA = 45 + 9 +6 + 2" or 4"
puts you really close to the edge depending on your decorative shell material.

[bentedesco]

Also, I'm sure you've seen the posts here, but the forum advocates using concrete pavers to elevate your Fb Board off the hearth. That will keep the boards from sogging up.

One thing I'm not clear about however is that if we do use pavers underneath the Fb Board if Weep Holes are still necessary.

[mongota]

What is wrong with people like us? How does it go from a couple hundred dollar suggestion to full blown thousands of dollars and months of work project? Am I alone here? Do other people suffer from this insanity?

My construction adventure started when we moved halfway across the country and were house hunting. Most every house we viewed was a compromise of some sort.

My wife said "Why don't we just design and build the house ourselves?" and I replied "Okay."

So we did. lol

The pizza oven was the same. We started out with a fire pit recessed in to a stone wall out by the pool patio, we used the fire pit for campfires and toasting marshmallows. It soon expanded in to: the current WFO build...plus a tandoori oven...plus a rotisserie platform for pig and lamb roasts, as well as a platform to have open fires upon...and while we're at it, we may as well throw in a station for a smoker and another for a propane grill!

And so it goes.

But I wouldn't change a thing!

[Dwatkins]

Russell,
Yes figures are accurate. It will be close but do believe that I have some room if needed. I drew it out and have measured many times and do not believe that I have missed anything. The exterior will brick all the way up. I will extend the pergola to completely cover the oven so not worried about moisture. If it is just for good measure to leave so holes just in case than can easily do so once I get ready to pour the floor and hearth.
Thanks for the response.
Dan

[Dwatkins]

Mongo,
Saw the post of your build.
Looks incredible!
Dan

[Dwatkins]

Russell,
Just a follow up to the previous post and I need to do a better job proofreading before sending.
My plan is to extend our pergola over the oven which will add a 14' x 12' roof over the oven. The interior brick wall will come up approx. 36" which will support the oven floor and plan to add angle iron with a center post for added support. The oven floor will stop at the center of the two rows of brick allowing the exterior to continue up to the pergola roof. I had mentioned that I did not believe moisture would be an issue but adding some weep holes in the floor just in case moisture does get under the insul board will not be a problem. I also was not planning to do stucco over the blanket/ chicken wire because I intend to add a loose fill to cover the oven once I have bricked the outer wall up to at least the height of the top of the dome. The other pics are my first load of old Chicago bricks (250 of about 1400), my new 10" Harbor Freight wet saw, and the starting lay out. For $250 w/ tax the wet saw performed exceptionally well for the few hours that I used it over the weekend. Considering that almost every brick will have at least two cuts to form the circle, it will get a workout.

[UtahBeehiver]

The circular base will give you good practice on the saw for your dome work. Being under cover will go a long way to keeping the oven dry. Dry pour over blanket will work great. You should have a very well insulated oven around the dome and with 4" of floor insul. the oven heat will last for days. Looking forward to seeing your build. I used the old cheap HF saw for my build and it is still hanging in there after a oven, patio and stone work. I needing to sell it off to make garage space but hard to let it go, right tool for the right job.

[Dwatkins]

Is there any difference between Aluminosilicate Ceramic Fiber Insulation Board and Calcium Silicate Insulation Board? The Calcium board that I found is 2", has a 370 PSI and rated to 1800F. Cost is about $10 sq ft.

[UtahBeehiver]

Forno Bravo actually provides AiSi with their kits. IMHO, here are the two critical specs you need for either AlSi or CaSi, compressive strength of about 70 PSI or more at 5% deformation (abt 0.5MPa) and 0.07-08 w//m.k at 400C thermal K factor. You could try looking for Thermal Gold 12 (CaSi) from Distribution Internation, think their corporate office is in Houston with a branch in Dallas or Austin. Some recent builders have been asking about InsBlok 19 but IMHO it is on the low side at 38 PSI compressive strength. The ovens we build are really really heavy.

[Dwatkins]

Russell, appreciate the response.

[Dwatkins]

I made a little headway this past week on the build but it is tough trying to do a project with a full time job always taking my time. Anyway, I made two different jigs that are working very well; the first is this piece of 2 x 8 cedar with a slight angle for cutting each end of the bricks in order to form the circle. I am not like some of the engineers on this site that I have seen that calculate out the exact degree, I use the TLAR theory, “that looks about right” and it works pretty well although I will probably be a little more detailed once I get to bricking the oven. Since the walls are round and it is critical that the walls are plumb it was going to be a challenge to hold a level to every brick going around and especially with each joint where two brick come together forming a point, so I came up with this jig. I got a 5/8” x 72” all thread and anchored it to the slab with two pieces of 5/8” plywood and then braced it off at the top so it was level. I then cut a 2 x 4 to 67 inches which is the diameter of the outside wall and drilled a 5/8 hole in the center. Slid it down the all thread where it sits on a nut and flat washed and now I can raise it up with each course of brick and as I lay each brick I can spin it or move it to line up the end of the 2 x 4 with the face of each brick. Now the face of each brick will be 33 ˝” from the center and should be completely plumb. Once I get to the oven floor height naturally this will no longer work but it is working well now. The interior wall is not as critical but I am following closely to the outside wall leaving a small gap.