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  #31  
Old 05-13-2013, 11:31 AM
deejayoh's Avatar
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Default Re: 42" in Portland OR

The fireclay is in the mix to provide strength after the oven is fired. Something about the lime and concrete breaking down in the heat over time, IIRC - I think the fireclay is what provides the strength long term. I don't know that it's really going to change the characteristics of how the mortar dries. Seems like the sand is what should keep it from shrinking but I'm really just guessing.

The arch looks good, but I can see you're going to have a fun time tying your dome bricks into the back of it. You might try using your IT to scribe a line into the back of the arch bricks to figure out where they should meet each ring of your dome, and then use a grinder to shape the back of the arch bricks. The approach with an axed arch like you're building is a little different than what you do with a true arch - but if you look around there are pictures to guide. I'll see if I can dig one up
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  #32  
Old 05-13-2013, 01:06 PM
david s's Avatar
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Default Re: 42" in Portland OR

Quote:
Originally Posted by portland_aaron View Post
I had gotten the recommendation to use a higher amount of fireclay in order to slow down the shrinkage / cracking of the mortar. If this hasn't been the collective experience of the group, should I go back to 1 part (rather than 1.5 parts)

Attachment 35601
no, you got that one backwards. The clay is what increases the shrinkage.stick to the recommended recipe and if anything, reduce the clay content to prevent shrinkage cracks.
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  #33  
Old 06-24-2013, 12:51 PM
Peasant
 
Join Date: Dec 2012
Location: Portland, OR
Posts: 25
Default Re: 42" in Portland OR

Attachment 36806Hi all, I have made some (slow) progress on the project. Have finally gotten over the entry arch, so all that's left is time!

I am at about chain 8, and starting to have issues with staggering the bricks. Inevitably, I end up with ones that line up somewhere in the chain. I have been using 4" rear measurements as per the great Excel calc that is on the site. I am contemplating reducing from half bricks to thirds - any reason not to?

Thanks for all the great help on this site. There is a wealth of information available here!

-Aaron
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  #34  
Old 06-24-2013, 01:09 PM
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Join Date: May 2012
Location: Utah
Posts: 1,549
Default Re: 42" in Portland OR

None at all, as the diameter of the dome decreases you will find that you will need to make adjustments to the brick width.
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  #35  
Old 08-26-2013, 07:18 AM
Peasant
 
Join Date: Dec 2012
Location: Portland, OR
Posts: 25
Default Re: 42" in Portland OR

Hi all,

It has been a little while since the last update, and more slow progress has been made. I have closed the dome and am now working on the vent area. Also, due to scope creep, I have decided that what the pizza oven "needs" is a built in BBQ next to it... so the project is taking longer than anticipated.

I am planning to use the 8" square clay flue liner to build the chimney section, supported off of an inner and outer vent arch. The sections that I picked up are around 16" in length. I am currently planning for 2 of these, purely based on aesthetics. Is there any consensus about length for the chimney? I have read many posts that say it isn't needed at all, and many that say it needs to be >4' high to draw effectively. Can I get by with one section of vent? Two? Three?

Also, I plan to cover the dome in vermiculite and stucco. I was hoping to do stone veneer for the chimney - which brings me to my big question; I would like to clad the outside of the firebrick vent and chimney area with vermiculite, allowing me to set the chimney shape. I am planning to wrap the dome in ceramic blanket and vermiculite over that. Is the blanket needed to wrap the vent as well? Are there concerns about using rebar in the vermiculite for additional strength?

How much strength will the vermiculite add? Is it at all structural, or just there for insulation? i.e. if I wrap the vent and chimney, do I need additional butressing or will the vermiculite mixture provide that?

Sorry for so many questions - I can start to see the light at the end of the tunnel, and am anxious to start using this thing. I would also love to get it waterproof before the rains start here in the Pacific Northwest. My wife has made it clear that the tent in the backyard is not her idea of high design...

Thanks for the help!
Aaron
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  #36  
Old 08-26-2013, 07:39 AM
texman's Avatar
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Join Date: Nov 2009
Location: Amarillo, Texas
Posts: 579
Post Re: 42" in Portland OR

Quote:
Originally Posted by portland_aaron View Post
Hi all,

It has been a little while since the last update, and more slow progress has been made. I have closed the dome and am now working on the vent area. Also, due to scope creep, I have decided that what the pizza oven "needs" is a built in BBQ next to it... so the project is taking longer than anticipated.

I am planning to use the 8" square clay flue liner to build the chimney section, supported off of an inner and outer vent arch. The sections that I picked up are around 16" in length. I am currently planning for 2 of these, purely based on aesthetics. Is there any consensus about length for the chimney? I have read many posts that say it isn't needed at all, and many that say it needs to be >4' high to draw effectively. Can I get by with one section of vent? Two? Three?

Also, I plan to cover the dome in vermiculite and stucco. I was hoping to do stone veneer for the chimney - which brings me to my big question; I would like to clad the outside of the firebrick vent and chimney area with vermiculite, allowing me to set the chimney shape. I am planning to wrap the dome in ceramic blanket and vermiculite over that. Is the blanket needed to wrap the vent as well? Are there concerns about using rebar in the vermiculite for additional strength?

How much strength will the vermiculite add? Is it at all structural, or just there for insulation? i.e. if I wrap the vent and chimney, do I need additional butressing or will the vermiculite mixture provide that?

Sorry for so many questions - I can start to see the light at the end of the tunnel, and am anxious to start using this thing. I would also love to get it waterproof before the rains start here in the Pacific Northwest. My wife has made it clear that the tent in the backyard is not her idea of high design...

Thanks for the help!
Aaron
The vermiculite mix has little if any structural strength. you will want some mesh on the vent/chimney to help hold it in place while forming. The blanket is not necessary for the chimney. You are trying to hold heat in the dome. (Do you have a heatbreak?) post a pic of your vent as far as buttress needed. The vcrete would have to be really thick to help buttress. I don't think rebar would help in the vcrete.

Texman
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  #37  
Old 09-03-2013, 07:42 AM
Peasant
 
Join Date: Dec 2012
Location: Portland, OR
Posts: 25
Default Re: 42" in Portland OR

I took the suggestions for buttressing to heart, and now don't think the side walls are going anywhere. I mortared on some 6X8X16 blocks, sunk some rebar into the hearth, and filled the cores with concrete. I borrowed a rotary hammer to pop the holes for the rebar - that thing was awesome! I can't think of a good reason to own one long term, but it sure made drilling holes in concrete easy. Since it went so well, I took the opportunity to run some conduit through the slab as well - perhaps I will end up with lights under the eaves of the chimney.

Those of you with an eagle eye might spot that the flue liner is not connected to the vent yet. For those that have used these clay liners - did you mortar bricks around them as well? Or will the liner (surrounded by vermiculite) be sufficient? Also, how many sections of these have people used? I like the look of 1, but want to make sure it draws well enough.

I also started the dome curing process this weekend - it has been sitting for about a month, as the vent proved to be more taxing than expected. I put a halogen worklamp in the dome for about 5 hours, and the temperature was at a pretty constant ~200. I will start the firing process next weekend. Question - does the type of wood burned matter for the curing process? I know that there are strong feelings against burning fir - will this get too much smoke and pitch stuck to the oven and make bad tastes later?

Thanks for all the help, this is an incredible wealth of knowledge.

I have put a couple photos on this post - the finished vent, the curing with a light, and the requisite keystone of the dome. Couldn't have done it without this site!

42" in Portland OR-img_2440.jpg

42" in Portland OR-img_2443.jpg

42" in Portland OR-img_2450.jpg

42" in Portland OR-img_2451.jpg
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  #38  
Old 09-03-2013, 11:13 PM
SableSprings's Avatar
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Join Date: May 2009
Location: Roseburg, OR USA
Posts: 193
Default Re: 42" in Portland OR

Your build looks great Aaron! I used the clay flue liners and mortared brick around the chimney for three reasons; 1) I liked the look better inside the den; 2) I wanted to protect the flue sections/joints primarily from outside influence & damage; and 3) I elected to use air space to insulate the liners...the quicker the liners heat up, the better the flue works to keep that hot air moving.

As to the total chimney height; I found that the initial smoke when I fired up the oven or when I added wood often came right down into my face and the "entertaining area". I added a section at a time until I found the right height to keep the smoke "out of my eyes". (I believe the building code in Oregon is the top of the chimney must be 3' above the nearest portion of the roof structure within a 10' radius...so if you don't have a roof, no problems there.)

I suggest you do look into a spark arrestor cap for our Oregon summer fire season. I leave mine on all the time because I'm in a grassland/forest area and it's not worth the extra fire hazard.

I honestly don't believe the kind of wood (untreated of course) makes a difference in the curing fires...other that you don't want to throw a large log of pitch in anytime. Once your oven is cured, you'll be burning off any accumulated wood oils/resins/creosote when you go for pizza temps. For my weekly bakes, I currently burn almost any kind of wood I can get to bring my oven up to 700F and then let it fully saturate & cool down for 575-590F bread temps. I do use apple or oak when I'm doing pizza so I don't get any ash pops or funky smoke flavors.

Double check your flue size...you want at least 8" inside diameter for 42" inside diameter oven. I bought the 8" flue (for my 39" id oven) and thought/assumed the 8" was inside diameter...not, so I get a little more smoke out the front of my oven than I believed I would (no big deal for me, but easy fix at this point for you).
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Last edited by SableSprings; 09-04-2013 at 09:40 AM.
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  #39  
Old 09-27-2013, 09:13 PM
Peasant
 
Join Date: Dec 2012
Location: Portland, OR
Posts: 25
Default Re: 42" in Portland OR

Plan, the insulation step is a pain! It took me all day to insulate the thing.

I have 3 inches of ceramic fiber insulation now, tied together and draped over the dome. I am doing the igloo style dome, so the dome will be subjected to the weather. My question is - do I need a perlcrete layer over the insulation followed by stucco, or will I be ok with stucco only? Obviously it will need some rebar, but is the perlcrete preventing any cracking / failing?

My theory is that any thermal expansion of the dome will be damped out by the insulation, and shouldn't translate to the outer layer. Am I at all right here?

Thanks for the help!
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  #40  
Old 09-27-2013, 09:47 PM
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Default Re: 42" in Portland OR

I worked on a build (shown below) that we "simply" cut/wired chicken wire over the insulation and then applied two coats of stucco (the first was a water resistant base material...looked just like mortar to me). The third picture shows the base coat (scratched so the outside stucco has something to "stick to"). You are correct in that the ceramic blankets act as an expansion damper...so putting a base wire mesh down and a couple of layers of stucco down will be plenty strong (as long as you aren't playing king of the hill on your oven.

In looking at your dome, you'll have several places around the chimney & vent that will need pretty thick stucco layer(s) to keep smooth lines. Although you don't need perlcrete/vermicrete on top of the 3" of ceramic, you might find it useful to use it to fill in and round out those spots before you stucco.

Though we used chicken wire on the CasaG90 below, if I had to do it over I'd certainly consider using metal lathe instead. It's a little more of a pain to work with, but it's designed to be the base for stucco and I think if you used it to mold/cover over the insulation it would make the stucco application easier.
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42" in Portland OR-dsc05034.jpg   42" in Portland OR-dsc05044.jpg   42" in Portland OR-dsc05050.jpg   42" in Portland OR-stuccofinish.jpg  
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Last edited by SableSprings; 09-27-2013 at 09:52 PM.
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