Exterior Dome Construction

[Bandrasco]

First off I want to say that I thought I was crazy (my wife included) at the thought of constructing a wood fired pizza oven. I've worked with stone and mortar for over 20 yrs so the basics I have down but this is beyond what I have in my brag book. Thanks to all of you that have taken on this task successfully I feel confident and I'm ready to start.

Like all things I build I sometimes get accused of going to extremes that are just not necessary. I think this project will give me more opportunities to do that then ever before. I've reviewed many of your designs, ideas, craftsmanship, and attention to detail to the point of mental overload.

Here are a couple of questions I have and would like the forum's input.

1. I am one of those who will go through great lengths to make a dome with very little mortar. With my stone and tile background I have no issues with multiple cuts on individual bricks, nor am I in a hurry. What/where is the best source to get this information on a 42" dome construction that includes the detail for cutting the brick courses so that the mortar is minimal (like Les') and the bricks are tight?

2. Here is where I go overboard. I think it's a shame to have to cover up all that hard work, craftsmanship, and detail on the dome you just spent months (I'm assuming) to create. I woukd like to have that same reveal on the exterior as well. Is it crazy to build in essence another dome? A dome within a dome. Other than hard work and time I don't see why it wouldn't work. I could still insulate the main dome either by doing it the conventional way and then constructing another dome to cover it up; or, build the second dome leaving a specific space between both domes and then fill it with a loose insulation or like flowable mortar. I've seen a few pictures of these designs and they appear to be old which makes me believe it's a sound idea; just a lot of work.

I'm a newbie in this forum but ready for any suggestions/advice.

Thanks in advance everyone,

[egalecki]

Re: Exterior Dome Construction

Here's one. I don't remember whether it had blanket or vermiculite concrete insulation, but it did have insulation. I think it would be easier to build it, insulate it, and then cover it with another dome, rather than try to fill in between two shells. Just be sure to use lots of insulation.

As for the first question, I can't help you. I'm not sure how the people who've done a lot of cutting came up with their plan.

[dmun]

Re: Exterior Dome Construction

The cut-every-brick plan is complicated. The first few courses are pretty straightforward because the vertical joints are close to perpendicular. As you go upward, the joints angle inward, meaning dual angle cuts on every brick side. Also, as you go upward the bottoms of the bricks don't mate very well with the course below, creating eye-shaped mortar joints. I think most people who have done it have done on-the-fly calculations, eyeballing each brick as it fits in. There is no reason, of course, why you couldn't plan every brick in a CAD system, but bricklaying doesn't lend it's self to thousandths of an inch accuracy.

As for the exterior dome, instead of a common brick dome, which would absorb water every time it rained, I'd think about doing it in terra cotta roof tiles, like the dome of City Center:



The tiles are harder than bricks, and overlap to repel water. They are also thinner to cut into fancy shapes.

[Bandrasco]

Re: Exterior Dome Construction

Thank you Elizabeth! This is exactly what I had seen and want to accomplish. I think you may be correct on the build, insulate, and then build process. It would at least give me the chance to bail out on the second dome if I get too frustrated...lol I don't think I will have any real issues other than time consumption.

Thanks again!

[Bandrasco]

Re: Exterior Dome Construction

Great Idea Dmun. Although tile is very dear to me I like the brick look. If properly insulated does the outer dome get very warm? If not then I have a waterproofing product that will not allow water to permeate through the brick. Also, if the temp is low enough I could put a vapor barrier of say Tyvek on top of the insulation/vermiculite just in case some moisture was to get through. Again, I absolutely love the look of the brick dome and if I'm going to build this to look as perfect as possible inside I want to take as much time to make it look just as good outside as well.

Thanks again Dmun, I appreciate the input!

[dmun]

Re: Exterior Dome Construction

If properly insulated does the outer dome get very warm?

I have a layer of the refractory blanket, and a bunch of vermiculite concrete on top of that, hard to tell how much because it's inside an enclosure. The outer arch gets hot from the radiant heat, but the other parts of the enclosure are hardly warm to the touch.

[asudavew]

Re: Exterior Dome Construction

I have an inch of therm blanket, followed by dry vermiculite --- 6 inches on the bottom 8-9 inches at the apex of the dome.

I followed that with and inch of mortar, then stucco.

It will get a bit warm to the touch on the outside.....But that's usually the next day.

Dave

[Bandrasco]

Re: Exterior Dome Construction

Thanks Dave,

This forum is loaded with skilled craftsman, great ideas, fantastic photos,and so much creativity that I could not sleep last night! I was looking at brick angles, mortar mixes, hearth designs, floor insulation at 3:55am...Yikes! There are so many ways to create a great looking oven along with being totally functional. I started my shopping list and think I'm going to pick up my bricks tomorrow. I really want to get a grasp on the cuts so don't have to stress about it later on... I'm sure that's going to come anyway .

Thanks again,

[Bandrasco]

Re: Exterior Dome Construction

I've seen many of you use a pc of steel with a hinge atached dead center of the floor using it as an angle/height guide. This appears to be a fantastic solution to the possibility of an out of round dome as you go up. I'd like to hear the forum's input on this technique.

Thanks again everyone, this is getting exciting!

[Bandrasco]

Re: Exterior Dome Construction

Ok everyone, I started! This last Saturday I made my final decision on location (luckily I already had a very thick sound slab in place), I placed and leveled out my first course of blocks, and then Sunday I ran the entire base, angle iron, holes drilled for rebar, bond coated the interior and exterior (it drove me nuts dry stacking them even though I knew I was going to fill them with concrete). I also moved the screen enclosure door, transplanted shrubs, etc (long weekend!). Monday night I cut my rebar, filled the holes with cement that had rebar, and then last night I cut and welded the rest of my rebar for the hearth. I know I could have wire tied it but hey, I never pass up the chance to break out the welder. Tonight I placed all my form boards in place and hopefully tomorrow I can poor my 4" of concrete hearth.

How long should I wait until I put down my vermiculite/portland mix? I am lucky enough to be in the stone business and was able to get a super deal on 5000psi Sakrete that will set in 24 hrs. Not that I'm in a hurry but I'd like to keep on schedule and start setting my floor this weekend. Too soon?

My fire bricks are cut, laid out, ready to go. Well the floor and the first course is any way. Speaking of the floor I had another question. Is it even worth thinking about laying the floor bricks on the side (2.25" length wise vs. flat on the 4" side length wise in an effort to gain more thermal mass? It doubles the bricks on the floor but I got a deal on them and believe I have more than enough. If it will in fact make a significant difference I'll make the change now. It will also allow me to fun the first course full brick without getting too high and then use the cut halfs there on up. Any thoughts on that one?

Thanks everyone, great forum

[mfiore]

Re: Exterior Dome Construction

What, no photos? We are suckers for photos.

Sounds like you are well on your way. Looks like you've accomplished in one weekend what it took me 3 months to do!

More thermal mass is not necessarily great. It depends on what you are planning to use your oven for. If it is too thick, sure it will have more retained heat (eventually), but will take longer to heat up and use more firewood in the process. I think these big, thick, high mass ovens are best suited for commercial use where multiple bakes are planned, with daily firings.

Just my opinion.

[Bandrasco]

Re: Exterior Dome Construction

Thanks Mfiore,

I took pics of every step along the way, I just didn't know if I shoyld post it to this thread or start another?

I read a bit more on thermal mass and you're probably right. I do plan on cooking just about anything I can fit in the door way but I'm sure pizzas, bread, and some type of meat over coals will be the most common.

Looks like a rainy day in sunny FL today and tomorrow but Saturday we are having a bitter cold front; all the way down to the 50's in the morning! Not sure what to do. Kidding, grew up in the beautiful city of Chicago, IL. Although I miss the people I absolutely do not miss the weather.

Knowing me I'll have a tarp up after work mixing cement and getting the hearth poored.

What do you think about the Vermiculite poor (or push I should say)? How long after I poor the cement for the hearth can I get that on?

Thank you again for the speedy reply!

[mfiore]

Re: Exterior Dome Construction

Tell me about it. Cutting bricks in 30 degree weather is not fun.

I'm not sure about the vermiculite. I did not use it for my build, using a FB insulating board instead (it's worth looking into).

From what I've seen with other builds, there doesn't seem to be a need to wait. People have put the vermicu-crete down immediately after the concrete. They can cure at the same time.

[Bandrasco]

Re: Exterior Dome Construction

Thanks again.

BTW, just previewed your photo album, great looking oven so far! I plan on having the same type of entry with the wider front. It will allow more people to see the fire while entertaining along with making it easier to get things in and out. Are you finished with your oven yet?

Also, how did you post your pictures? Did you post them as-you-went, or all at one time? Should I post them on this thread or start another?

Sorry for the thousand questions,

[CanuckJim]

Re: Exterior Dome Construction

The major benefit of stacking the floor bricks on edge is increased mass. This will mean that you can in effect store more heat for more bakes in succession without refiring, but it also means that your firing times will be increased. If you plan to do multiple bakes, it's the way to go. If you want quicker heat ups for pizza, lay them flat.

Jim