I'm back

[Amusinglisa]

The inner arch is up and the form is out! We got most of the next row of bricks u, but have to figure out how to do the row above the arch. We will get this!

[SableSprings]

Looking good...I'm sure you'll figure out the arch row just fine. (And remember that mortar is your friend and the insulation blanket covers ALL areas that don't present well artistically ). Your instincts are good and there's lots of support here for you.

Pizza's starting to come into view on the horizon

[Amusinglisa]

Thank you SO much Mike! You inspired me to get the dome completed today. Remembering that Mortar is my friend, I shamelessly used bits and pieces and a few hammer taps to fit the last bit. (Photos are a little out of order).

Now on to the entry archway and chimney. I am handing over a small batch of vermiculite mortar to an artist friend who will be sculpting the outer layer. If we work hard, maybe we can have a going away pizza party before the kiddo heads back to college on the 24th! (I don't actually need insulation, etc for one firing, do I?)

[Amusinglisa]

I need help wrapping my brain around chimney requirements. Is there anywhere I can get specific information on how/what/where of chimneys?

[SableSprings]

I'm glad to have helped your psyche for the last push to close the dome...but you were doing this build, so give yourself a big pat on the back!

First, you don't want to fire up the oven for pizza without going through the curing process. If you find yourself in the situation of being partway through "the cure" firing schedule and want to have pizza...I'd suggest you go to Costco or a local large grocery store and buy either the ready made skins or pizzas. Doing one of these in a 400-500F pizza oven is not top of the line ...consider it just another step up to the great pizza you'll be doing when "the kiddo" returns at Thanksgiving or Christmas.

As to chimney requirements, Russell's photo in post #11 shows you how the outer arch is larger than the inner arch. He pointed out the importance of giving yourself a reveal that allows a door to close the oven. Here's a couple of rules of thumb that you need (or should--IMHO) to incorporate in the vent/chimney design. Think of the space just outside the oven arch. When smoke/heat escapes the oven it comes out at an angle and up (fast). You want to create basically a smoke collection chamber (like a hood over most inside kitchen ranges) to collect and funnel into your actual chimney. Height of the chimney has a lot to do with simply getting any startup smoke to exit above the crowd, so to speak. Certainly, the taller you make your chimney, the better it will draw...but for most folks a chimney that's 3'-4' above the oven is plenty good. There are a lot of excellent builds that do not have an outer arch or chimney...smoke simply comes out the front and up (think adobe ovens in the southwest).

If you are doing the outside arch and chimney then conventional wisdom is that you want the outer arch to be at least 1" to 2" wider on each side than the inner arch. You want to create a smoke collection chamber that's 1"-2" wider than the oven opening and comes out between 13"-15" from the inner arch. Basically you want to build a rectangular "inverted funnel" that feeds into your chimney pipe that straddles the tops of the inner and outer arches. I hope that makes sense. It's not critical to create this size smoke chamber, but it's well worth a little extra effort (actually, just being aware while you're doing the outside arch lets you create a good smoke chamber).

For ovens that are 36" inside diameter, a six inch chimney pipe is the norm. When you get up to >38" inside diameter, the convention is to go with an 8" chimney. There's a topic section in the Forum that deals with Design Styles, Chimneys, and Finish that has several excellent threads.

Hope this helps and that I didn't put you to sleep with my droning on...

[Amusinglisa]

Thank you Mike! This is exactly what I needed.

Details: The smoke collection chamber coming out between 13" and 15" - do you mean it is ideally 1" or 2" wider than my opening and 13-15" into the "landing tunnel" so that the outside arch is then 13-15" away from the inner arch?



I'll go find that thread. I was searching, but now that I know the title (and have my reading glasses =) ) it should be easier to find.

[UtahBeehiver]

To add to Mike's detail explanation, I notice in one of the pics a double wall chimney pipe laying on the ground behind the cement mixer. Is this going to be you chimney stack? Typically the manufacturers make an adapter plate so you can mount the stack to the masonry fire brick. As far as the rectangular vent opening Mike talks about it needs to have a minimum of the same square inchs area as the circular area of the chimney vent, example say the chimney is 6" ID, are is pi x r squared (3.14 x 3x3 = 28.26 square inches) so you fire brick vent opening needs to be at least the area as well as being able to have material to mount the adapter plate to.

[Amusinglisa]

OH!!!! That was leftover from construction on my house. I was hoping it was what I thought it was. I am going to take it to a construction-guy neighbor and confirm. Since it is a left over, I do not have the adapter plate, but I am betting I can figure that out.

Do I need a metal vent or is brick sufficient? If I can just go with brick, I will get that knocked out today and see about beginning the curing process...

Kiddo will be home to help send the turkeys to freezer camp in November. If she brings a college friend or two, we can make it a pizza party!

[Amusinglisa]

OK. D.A.Q.: My oven was started last June (2016). It was completed up to the third row of bricks on the dome and stood for a year (in the weather - eek). Is there a need for the week-long wait before curing fires? I am having a sculpter do the final art-y finish (it will be a kelpie ala Falkirk) but may cover with ceramic blanket now, tarp for rain (I have killer tarps) and do final finish a bit later...

[UtahBeehiver]

Short answer is yes,we see this quite often where there is a rush to cure the oven and it ends up cracking. As Mike said, be patient, do it right, so all you hard work will pay off. You can do some cooking with the cure heat but you really need to do a slow cure.

No you do not need a metal chimney, I just saw it in the background. It does need to be a type A all fuel rated vent, not a type B natural gas vent.

[Amusinglisa]

AH. Planning on a slow cure for sure -- I'll take all the time I need for that and do it right. Just questioning whether I need to wait a week before I start the first fire, as all my uncured mortar is only in the top 6 rows of brick...

[SableSprings]

Details: The smoke collection chamber coming out between 13" and 15" - do you mean it is ideally 1" or 2" wider than my opening and 13-15" into the "landing tunnel" so that the outside arch is then 13-15" away from the inner arch?

Yes, the chamber you are building above your oven opening is wider by at least that couple of inches (on each side) and the gap from the outer edge of the inner arch is 10"-12". Sorry, I didn't really express that very clearly. When you build the outer arch, you are simply trying to space it out so the hood you are creating (above the oven opening) is big enough to contain (and funnel) the exhaust into the chimney pipe. Say your oven opening is 18" wide (to accommodate a full sheet pan ), that means ideally the open space/gap above the landing would be 22" wide and 10"-12" deep. Placement of the outer arch in that position not only sets you up for a good smoke collection area above the oven opening, but for an adequate space below for the reveal and for maneuvering the fire door. (The arch shape will provide the 3rd dimension--height of the chamber--as you will place the chimney pipe at the top of the gap between the two arches.)

The depth of my smoke collection chamber is too shallow at about 9" and smoke will occasionally roll out the front of the oven when the fire "burps". I built my front arch too high and too close. I'm now thinking about lowering my front arch by a couple of inches. That will increase the size of the smoke chamber and pretty much eliminate that "problem".

...and yes, do let the mortar cure for at least a week or so before you start the curing fires, especially since there is such a time gap between the two dome mortar sections. Remember heat rises, so your newly mortared area will be the most impacted by any fire in the chamber.

[Amusinglisa]

OK. Reeling in on the curing fires, then. Thank you.

We got all the daylight specks filled and the outer arch mostly done. I am going for the shape requested by my sculpter, so thinking I will now work with a metal vent and put it a bit below the gap here.

Ceramic blanket and IR thermometer on the way and I am off to the neighbor for some advice on whether I can fiddle with this chimney...


Oh. Chimney in photos has been kicked, somewhat flattened - I'm guessing by a horse... It won't fit a vent now. DANG!!

[Amusinglisa]

[SableSprings]

Two things of which to be aware.

1) Your latest addition to the oven will need some buttressing. The arch is tall, which means the outward forces will be pushing the lower portion of the arch apart...not good, but easy to fix. Simply plan on some full size bricks built up on each side to keep them from moving out over time (and as weight is added above). I think this is type of buttressing is very commonly used on the sides of the vault connecting the outer arch to your oven and obvious in Russell's picture (and also noted in my build as well as many others).

2) Your exhaust gasses are going to come out of the oven opening at an angle--not straight up. That's another reason for creating a smoke hood/collection area with some depth...it catches that smoke and helps direct/allow it time/space to feed into the actual chimney. This is especially important early during firing - before the flue starts getting warm and drawing well.

In looking at the picture of your partially created (and brilliantly braced I might add ) beginning of the vent outer arch vault, it doesn't look like the reveal on the oven's opening is smooth and level/flat around its perimeter. If that's the case, making a door to fit and seal is going to be a nightmare. While it's accessible (if my view of the reveal is correct), it would be wise to take the time to fix that (possibly with a grinder ).