39" Pompei build in NH

[SableSprings]

Russell answered your question pretty well for both of us Marc. My oven opening is a bit different than Russell's (I used angle iron) with a rectangular inner "arch" but the same answer applies...my outer opening could be lower without impeding my door. I've attached a few pics to show the front of my oven so you can better envision how easily I could have lowered the outer arch if I would have known it would be an issue (albeit a minor one ).

The last picture shows my fire door (closest to the reveal) and my pre-paint "working" door (sitting on the outer landing) to give you an idea of how much head room I actually had to work with. (p.s. The object hanging down on the right side of the door shot is my LED BBQ light so I can see into the oven when it's dark outside )

[ML38]

On your first picture in post #22, it looks like there are spaces behind the front buttress bricks. Is that a space that will be filled or is it just an illusion? If it's a space, being an over-achiever , I'd put in a couple sticks of rebar that lean toward the chimney and then fill it with left-over brick pieces, mortar, and/or concrete to make it solid. !

I am filling the voids with mortar to make it solid. I'll add some rebar also,

I finished my vent today. I'm pretty happy with it except it ended up a bit above what I expected because of the difference between dry fit and adding mortar. I will have to wing it trying to get the surrounding surface level so I can start the chimney. I'll also have to add another external arch to support the front edge of the chimney because it needs to come past the existing arch.

Insulation next before continuing with buttress/chimney work so I don't interfere by mistake and so I can get started with curing the dome.

Pics of the vent

[SableSprings]

Looks great Marc! Glad to hear that you'll fill the voids...I angled my rebar towards the arch from the sides in my "buttress voids fill" thinking it might be stronger than just putting them in vertically. Also, my smoke chamber to chimney interface has the same "sharp edges" and creosote does collect there (and sometimes drops down unexpectedly ). I also did the "oops" with cutting my arch bricks and not taking into account the mortar. It seems like almost every build on the forum has a time of "...well, I'll have to wing it..." so you'll figure something out and I'm sure based on what you've done so far, it will end up looking (and working) fabulous)!

If you can, I'd recommend taking a grinder to the underside of your brick, chimney top plate to round off the edges a bit. It will make for a smoother flow and less creosote buildup. Hope that makes sense...I want to do that to the top corner/space areas of my collection area, but it's going to be a double pain of access and cleanup (so, it's been easy to put off ).

[david s]

Be careful using rebar in high heat areas. The reason stainless steel needles are the recommended reinforcement is because their small size produces a much larger surface area that they can dissipate their heat to the surrounding refractory. Rebar can't do this and because steel is way more conductive than brick or refractory it gets hotter and expands. Rebar is also prone to rusting and heat accelerates any corrosion. Problems may not be evhttps://community.fornobravo.com/forum/pizza-oven-design-and-installation/other-oven-types/398266-mobile-deconstruction?p=398422#post398422ident for many years but may show up in time. Check here https://community.fornobravo.com/for...422#post398422

[SableSprings]

You are right about the expansion David, and a good point for all oven builders to know. The void/buttress area Marc is filling (and using rebar in) is just outside of the dome insulation...so there shouldn't be any heat expansion problems. If you look at the first pic in Post #22, you can see the left and right side "empty pockets" being addressed. Definitely I agree, if I was doing a cast oven and had leftover stainless steel needles, I'd try to use them up in fill areas like this...

[ML38]

Thanks for the replies. Like Mike said, I don't think high heat will be an issue.

I had a lot going on this weekend so not much oven time. Got the insulation on and filled a large cast iron frying pan with charcoal briquets for 5 or 6 hours. Dome got to 200 F. Which brings me to my question of the day:

I should be able to work on putting lath over the insulation while having a small wood fire going right? with the exception of avoiding the smoke...

[SableSprings]

Thanks for the replies. Like Mike said, I don't think high heat will be an issue.

I had a lot going on this weekend so not much oven time. Got the insulation on and filled a large cast iron frying pan with charcoal briquets for 5 or 6 hours. Dome got to 200 F. Which brings me to my question of the day:

I should be able to work on putting lath over the insulation while having a small wood fire going right? with the exception of avoiding the smoke...

No problem working on the lath & insulation install while beginning the curing process (other than smoke as you said ). I like the charcoal briquettes in cast iron pan for the initial steps of the cure...sure makes a difference in avoiding the big early temp spikes you can get by saying, "Well, how could and extra piece of wood or two hurt?" I also appreciate that you can move the pan around and that it makes the "ash cleanup" a breeze.

[ML38]

Day 2 of curing. Got the upper dome to 350F most of the rest was 300-320, had it going for 4 hours. Smoke wasn't a problem. Got the lath on except for around the entry. I put some screws into the cement around the dome to wire the lath to and then made some cuts so I could overlap the lath and make it as round as possible from the start. Worked out pretty well.

Next step is to get the first couple courses of the chimney surround on so I can do a base coat up to it. Also put the concrete around the whole thing with a slight angle away from the dome. See the first pic (sorry for it being small) for a very rough sketch of what I'm thinking of doing to get the water to flow away from the dome.

[ML38]

Question on curing:

If I can only get 3 1/2 to 4 1/2 hours of fire on a night, how should I change the prescribed schedule for curing? Last night I got it up to 350 for a few hours then let it die out so should I repeat tonight so I get 6 or 7 hours at that temp basically doubling my cure time? Also, it's that time of year when the nights get cold and damp so will that change anything?

Thanks

[SableSprings]

Nice job on the lath Marc! I hated cutting that stuff...seemed like it cut me as much as I cut it . I do like the insulation on first, then the curing fires choice. I know you can do it either way, but I really think a slower cure this way is worth it. For my money, I'd repeat your 350F fire tonight for the 6-7 hours and then bump it up to the next level tomorrow for the 4ish hours, followed by another 6-7 hours at that level. After that I'd fall back into the normal cure timetable. It's two extra days of curing, but IMHO, during the most critical mid phase and worth it.

Do you have a door made yet? If you do, after the evening fire has died way down, put the door on the landing leaving a small gap. This will help the retained heat continue to force moisture in the outer layer to exit and leave a little interior air flow/transfer. Here in Oregon, I know those cold and damp mornings too .

Also, I know many folks might think this overkill but I'd consider putting a bead of silicone seal around the base of your lath where it meets the hearth concrete. That would add an additional moisture barrier to any water that will attempt to move in between the hearth/sloped concrete seam towards your insulation batts and board. Hard to believe sometimes how water will wick through "impossible" places by capillary action.

[ML38]

Do you have a door made yet? If you do, after the evening fire has died way down, put the door on the landing leaving a small gap. This will help the retained heat continue to force moisture in the outer layer to exit and leave a little interior air flow/transfer. Here in Oregon, I know those cold and damp mornings too .

Also, I know many folks might think this overkill but I'd consider putting a bead of silicone seal around the base of your lath where it meets the hearth concrete. That would add an additional moisture barrier to any water that will attempt to move in between the hearth/sloped concrete seam towards your insulation batts and board. Hard to believe sometimes how water will wick through "impossible" places by capillary action.

Mike,

Do you think the bead of silicone would be sufficient to replace my idea of a sloped concrete that the render layer would partially cover? I'd be happy to not have another step with concrete. Running a big bead of silcone would be easier.

I attached my sketch again but normal size this time.

[SableSprings]

If you don't want to do the sloped concrete Marc, the well applied (doesn't have to be thick) silicone bead around the outer stucco render would do pretty well at stopping a seep along the hearth seam. You might even think about laying a bead of silicone around the outside perimeter of your ceramic batting and then setting something like a vinyl cove wall base on top of it (see below link). That would not only stop the horizontal seep, but really impede any up and over capillary action. Kind of establishing a higher water barrier between the batting and render. The only caveat is that you need to maintain that outer render...water seeping through it into your insulation then becomes trapped at the bottom.

As David S promotes, using an acrylic paint (powder you mix up...not a wet premixed version) over the final render really makes a good, longer term dome waterproofing. Also some products on the market that are added to the stucco to make it waterproof. (Do a Google search on xypex). Also an option to do the paint-on waterproofing between the outer two layers of stucco with something like ReGard (several products like this are used primarily for shower basepans).

Here's a link to one type of vinyl cove wall base carried at Home Depot...just to give you a visual on what it is.

http://tinyurl.com/ybozzojt

Be aware, that short of putting your oven under cover...eventually (without maintenance), water will find a way into the oven's insulation. The good news is that after a couple firings, the water is driven off and your oven is back working at top efficiency.

(Again, I tend to overbuild and overthink...)

[ML38]

So I made some really good progress today and totally improvised with every couple bricks trying to get it to look half way presentable. I ended up using some granite pieces from the part I cut off to top off the side flat parts. For a complete amateur I'm pretty happy with the look and I think it will hold up to any stresses from the weight of the chimney. ( I hope ). I didn't have any curing fires since the back of the chimney is actually touching the top of the internal arch and I need to let it cure on it's own for a bit. If anyone thinks it's still OK to have one tomorrow then let me know and I'll fire it up!!

Here are some pics form today's progress. The last pic is my scrap pile and left over bricks. Pretty efficient for an amateur if I do say so myself.

[ML38]

I have a stucco/render/finish coat question:

The big box stores around here don't seem to carry stucco so I looked up the 'homebrew' version.

What I found was a 1 part Portland, 1 part Masonry Cement and 2 1/2 - 4 1/2 part sand. sounds like I could also get away with one coat of it then one finish coat with white portland cement so I can add color.

Here are the questions:

Is this recipe a good one for this application?
Will one coat work plus finish coat in this application?
Is Type N masonry mortar OK to use?


Curing fire for a couple hours tonight. hard to find the time but now that all the mortar work is done with the entrance I'll be able to do more. What's left of Hurricane Jose coming tomorrow and Weds so nothing going to get done til that passes.

[UtahBeehiver]

I see you are located in the NE ( your winters, like Utah can be tough on ovens) and if you oven is going to be exposed to the elements and not enclosed you need to put the best stucco and outer coating possible, ie acrylic additives and outer coats. Most big box stores no not carry the high end stucco products you will need to go to where the trade people go. Most cases they sell to the DIYers as well and give you some sound advice.