Casa2g90 Install in Portland, Oregon

[ASPLM]

Heres my latest questions

1) One of the oven sections seems a little wobbly on the insulation base. Does it all firm up once you mortar the three sections together, or do I need to put some kind of shim under the base edge of the oven to make it more stable? And if so, is a chunk of concrete a good choice, or will it have problems being that close to the heat source?

2). Above the suggestion was made that I put a bead of high temp mortar around the edge of the pavers and paint it with redguard. Do I just paint he bead, or extend the redguard up over the lip and completely cover the exposed pavers to the edge of the insulating later. I don’t want to make a basin of redguard that actually traps water under the oven.

3). As you can see I have an 8” landing in front of the oven opening. Any special considerations for the material I use to put there? I have some standard concrete brick pavers left over from the patio that I’m considering there, but will I have heat problems?

4) Also referenced above, I painted a broader footprint of redguard than intended because I’m a dummy. Does the fact that it extends out past the pavers present any concerns? Should I scrape off the excess?

[UtahBeehiver]

Can you tuck and point with some of the refractory mortar you will be using for the point seams? IMHO, you should be fine with pavers in front of the oven. The refractory tiles are in the vent chamber although there is radiant heat coming from the oven, I don't believe the temp will get high enough for portland degrading. Did you drill holes in your hearth that was mention in previous psost? This will solve the redguard basin issue.

[ASPLM]

I did put in weep holes.

[SableSprings]

The Casa2g90 build I was involved in had a similar "wobble problem" when we set the pieces onto the ceramic board. We knew that the dome pieces would move a bit with the heat expansion and just used the refractory mortar as instructed over the seams. My main concern when we set the dome pieces into place was that the cooking floor plates buckled just a bit. It appeared that the only time we'd catch an oven tool was when we pulled ash/coals out into our ash dump...so ultimately the slightly uneven floor doesn't affect our use of the oven.

That said, if the wobble is significant or even just if it bothers you, then Russell's suggestion of using refractory mortar to level is a good one. You could also just pull some tuffs of the ceramic blanket material off and use that to stop the wobble

As to the water dam and Redgard around the perimeter question...remember, you're just trying to stop moisture from coming in from the edge seams. If you still have some Redgard left, I'd lay a large "mortar bead" maybe an inch wide and an inch high around the dome/landing perimeter (would not have to be refractory mortar...just buy a bag of regular type N, it's pretty cheap and you'll use it during your build/facade/finish). When the mortar dam is set, paint an inch or so out onto the hearth slab with the Redgard and then continue back & up to the top of the dam. This should keep the water from seeping into the board and if you put your ceramic batting in so it stays just on top of the bead, it shouldn't be able to wick up any water from below.

If you just want to use up some remaining Regard, you could paint up the sides of the pavers...but I don't think it would be worth buying more of the stuff. I think your weep holes, Regard, paver structure/layering is going to be pretty effective to minimize water coming in from below.

It would be useful to embed some bent nails or hooks into the wet mortar dam so you can easily tie the ends of your chicken wire wrap for the batting & render base. You can even buy some nails or screws for concrete and secure them into the base hearth perimeter. If you did this first and left 1/2" of the nail/screw above the intended height of the perimeter bead/dam of mortar it would give you a mortar laying guide and increase the attachment strength of the dam.

Looking good so far! Hopefully it will stay reasonably cool this week so you can work without being a sweat bomb.

[ASPLM]

Took a brief break for the Fourth, but back at it!! Insulation was surprisingly easy and lathe was surprisingly fussy. Did two nights of charcoal fires, which barely hit 250 at best, but I’m stunned at how long the oven holds its heat. 24 hours later and still running 120F. Pretty neat. Tonight I start my first stick fire and try to get it to 300F.

a question about Stucco:

I’m not sure if I’m going to put a brick arch on. If I stucco the front, how badly will that complicate an arch in the future?

Also, do I need lathe on the front of the oven for that stucco layer, or can I just put a couple thin cosmetic front layers right on the concrete?

[ASPLM]

Oh yes, also, how stiffly installed should the lathe be. I’ve got all the edges down, but should the “cage” be super rigid? Isn’t it mostly just like rebar at the end of the day, adding an interstitial framework for the concrete stucco?

[SableSprings]

I'm thinking the future brick front arch would basically just be a facade. There won't be any upper chimney weight on it and as a decorative front adding a little gap between the stucco and bricks would provide a nice little expansion zone which you could easily fill with a little fiberglass stove gasket.

If you put stucco on, it should have the lathe as a base/interstitial support layer. I'd maybe roll the edges back a little bit so you don't end up with any sharp lathe edges around oven opening and make sure the metal is well covered. Having the stucco edge back a little from the actual refractory would seem to be a good idea because it will get some "hits" from wood, doors, (and heads ).

If you look back at the pics in post #10, you'll see we did not extend the chicken wire out in front -- but I'm amazed the stucco hasn't separated more. Also, we do see some soot build up on the front of the oven stucco. I think it's mostly because we use a lot of pine wood. It washes off fairly well, especially on the embedded tile, and it hasn't been anything other that a character builder for the oven.

[david s]

Oh yes, also, how stiffly installed should the lathe be. I’ve got all the edges down, but should the “cage” be super rigid? Isn’t it mostly just like rebar at the end of the day, adding an interstitial framework for the concrete stucco?

I gave up on lathe or chicken wire years ago as it’s very time consuming to apply and to ensure it sits in the middle of the stucco layer. Random fibres in the stucco mix are way easier and faster as well as allowing you to make a much thinner shell. There are lots of types, but i’ve Now settled on AR glass fibres which are nice and easy to work with.

[ASPLM]

Well I’m not taking it off now!!

So anybody want to hold forth on their favorite brand(s) of stucco?

[david s]

Well I’m not taking it off now!!

So anybody want to hold forth on their favorite brand(s) of stucco?

No, of course not, but an idea for when you build your second oven.

[ASPLM]

Lit my first real fire last night after two nights of charcoal that both soaked to about 200F. My maple took a bit to really get going, but once it did, boy howdy. It’s not a fan of staying cool.

Regarding the curing process: the roof got up to 600F from time to time. When I finally damped the fire, the whole oven was soaked to 350F. It was still at 220F this morning (which is neat). So is the soak temp what I need to be shooting for? Or is letting the top of the dome get to 600 bad and I simply need lower, slower fires?

[UtahBeehiver]

During the curing phase is where we see a lot of builders get impatient and fire too fast, too hot, to quickly which results in cracking and oven damage, You need to slow down and gradually increase temp. One additional piece of wood can really spike the temp. Take your time so you do not damage all that hard work you did building the oven.

[ASPLM]

Thanks! So when I'm firing the oven, I'm shooting the laser on the walls, dome and floor. I'm guessing I want to avoid exceeding the max temp for that day on any of those surfaces (today will be 400F) and keep fire going until the soak temp on all three is 400F, then douse the fire and close the door, right? It's really hard to get up to the desired temp without overheating the dome, which I guess is why it needs babysitting and 4-5 hours of fairly constant attention (something hard to come by on a weeknight).

[ASPLM]

Well, after a nice slow ramp over 6 days from 200 to 600, I did the scary fire today. The top of the dome has cleared nicely revealing that I have a few minor vertical cracks, which based on my reading of the forum means... that I’’ve built a refractory cast oven and built hot fires in it and now I’’m part of a not very exclusive club .

Will the sides of the oven clear eventually as the oven seasons more? Do I need another scarier fire to make that happen? Am I ready to stucco?

[SableSprings]

On a cured oven, clearing starts at the top and moves down the sides...remember, heat rises--so the top of the dome will always heat faster. I usually fire my oven late at night for a bread bake the next day. If I haven't put in enough wood to saturate the oven enough, I'll often have a lower ring of "dark brick". I simply move the remaining coals to the outer perimeter and clear that lower ring with a bit more wood on those coals. When the oven has completely cleared, I dampen down with my fire door and let the oven's temp completely equalize. When I've got a pretty consistent temp on all surfaces, I start bleeding heat toward my target bread bake temp of 575F. Obviously for pizza, you're not dampening and cooling, but the clearing pattern is the same.

To check if the moisture has been completely driven off, place a piece of clear visqueen over the oven's insulation batting during your firing and look for condensation. Once the oven has completely cured, there will be no condensation. At that point, you can do your stucco.

...and welcome to the all inclusive cracked WFO club