36" WF Pompeii Oven in Maryland

[bentedesco]

Hi Everyone! I've been planning my build for a while and finally I poured my slab yesterday! It feels great to be getting started! While I'm anxious to continue the build, with all the rain we've had in Maryland over the past few days, I want to wait to make sure its solid enough to start building up. I'll probably start laying my base mid next week, in the meanwhile, I figured I would start documenting the process.

One unique aspect of my design is that I am going to try and attempt to make this oven semi-permanent. My Grandfather is in his 90's and is from Italy. We've wanted to do a build together, however, I probably will only be in this house another 2-3 years. Given that we don't know what the future holds, We decided to try and attempt to design our oven in such a way that I can use a skid loader + flatbed to take this with me when I move as this oven will have special significance for me family. (I'm sure I will need to go back and do some patching with after transportation, but its worth at least attempting this while we can).

Right now, the idea is to pour an incredibly reinforced slab and then float the first layer of cinder-blocks horizontally on the slab to allow the skids to pick up the oven. I'm thinking that I might have a 50/50 shot that it could work, however, given the significant to my family, it's worth a try. (Once I get to my future home, I'll pour a new foundation and mortar the bottom cinder blocks down, I even don't mind rebuilding the base and just reusing the hearth/oven). If any of you have ideas how I can further reinforce this oven, I'm more than open to your thoughts, but I am pretty determined to at least make this attempt with my grandfather. If nothing else, at least we will be able to still enjoy the oven here before I move in a few years.

Also, I'm planning on using brick to build my chimney up and it will be tapered at the end (I just couldn't figure out how to do that in the Cad program)

[david s]

[QUOTE=bentedesco;n40690

Also, I'm planning on using brick to build my chimney up and it will be tapered at the end (I just couldn't figure out how to do that in the Cad program)[/QUOTE]

No doubt you will also encounter similar difficulty tapering the chimney using brick units.
Because of the extra weight of a brick chimney over an arch it is recommended that the arch walls be buttressed to handle the extra stress.

[bentedesco]

No doubt you will also encounter similar difficulty tapering the chimney using brick units.
Because of the extra weight of a brick chimney over an arch it is recommended that the arch walls be buttressed to handle the extra stress.

Good call there david s, regarding the buttress. I like the look and durability of brick, however, I haven't considered the need to buttress a brick chimney.

JRPizza did a nice chimney build on his unit where he had a nice brick stack with an 8" pipe at the top

[mongota]

To make it moveable wirh a brick chimney? Id consider designing/building the chimney to be independent of the dome. The chimney would be piece #1. The dome and dome slab would be piece #2.

[bentedesco]

To make it moveable wirh a brick chimney? Id consider designing/building the chimney to be independent of the dome. The chimney would be piece #1. The dome and dome slab would be piece #2.

The more I think about what you and Dave S have said, while I like brick chimneys, it makes sense to go with a stovepipe here. Also reducing the bricks would take some weight off the base & the flatbed when I attempt to move it. Great ideas guys, thank you so much!

[bentedesco]

I've been working on designing my base and trying to ensure the correct height for the oven.

Right now, it's looking like my oven cooking surface will be about 44" high, is this too tall?

I've worked the calculations as follows:

Base: 32" (4 rows of 8" blocks)
Hearth: 4"
Cement Pavers: 2"
Fb Board: 2"
FireBrick: 3 1/2"
Mortar + Margin of Error: 1/2"

Total: ~44"

[UtahBeehiver]

Depends on your height, everybody is different. Typical rule of thumb is elbow height.

[Gulf]

I agree. But, I think of the elbow as the minimum height. And, the base of the sturnum (xiphoid process) as the maximum height. In my case that is about a 4" difference. The max works better for me as I don't have to bend over to see the back of the oven. For you, I suggest a cardboard mockup of your oven floor and the opening of the entry. From that, you will be able to fint the correct (ergonomic) height for you .

[bentedesco]

I agree. But, I think of the elbow as the minimum height. And, the base of the sturnum (xiphoid process) as the maximum height. In my case that is about a 4" difference. The max works better for me as I don't have to bend over to see the back of the oven. For you, I suggest a cardboard mockup of your oven floor and the opening of the entry. From that, you will be able to fint the correct (ergonomic) height for you .

Awesome! Thanks for the tips!

[bentedesco]

Today was a GREAT day. My father helped me get the base built.

Tomorrow, I need to get 3 more cinder blocks to finish the base and 20 more bricks to complete the form for the hearth and cut the rebar to reinforce the structure.

Hopefully this week I can get the framing for the Durock complete so I can pour my hearth next week!

One question regarding weep holes. Have any of you simply inserted 1/2" PVC tubing into your concrete mold and then poured the concrete around it? I'm thinking this would save me from having to drill into my hearth after the concrete cures.

[UtahBeehiver]

Yep, that works, a lot of builders forget hence need to drill afterwards

[bentedesco]

Yep, that works, a lot of builders forget hence need to drill afterwards

One last question about weep holes, I'm going to be pouring my slab tomorrow and I just wanted to confirm that the weep holes only need to be underneath where the CaSi board will be, correct?

Also, I was thinking about having 5, 1/2" weep holes in an X pattern (one in the center). Would this potentially weaken my hearth?

The other design I had was to do a cross pattern going down the center (from the back of the dome to the front arch). While this might have better functionality, I was worried that 3 holes down the middle of my slab might weaken it?

[david s]

You can use some polystyrene plugs cut to length and insert as you lay the concrete. I also like to dome the slab up in the centre slightly so the centre is about 10 mm higher than the sides. This encourages water flow away from the dome and won’t pool under the floor. You can also raise the insulation off the surface of the supporting slab with something thin like 6 mm gal steel mesh or concrete pavers laid with gaps between them to provide a passageway for water/steam to the weepholes.

[SableSprings]

Your rebar lattice within the concrete top slab is providing a lot of structural "strength". Those weep holes will not weaken your slab in either pattern you suggest. And yes, you are putting weep holes only under the insulation board. Remembering to place your 1/2" tubing pieces into the form work also has the advantage of keeping you from hitting a piece of rebar during the "drilling option". Another option to David S suggestion above is to drill holes in your support board and push the tubing pieces just through that board. I would cut the tubing off just below the top projected level of the concrete. I know this may sound stupid, but take some bread wrapped in a bit of plastic wrap and make a taller "cork" for each tube that will stand above the finished concrete.

When the concrete is poured, leveled and just starting to stiffen, locate your "bread corks", make a slight depression around each tube that will collect water and drain directly in the tubes. Gulf put pieces of screen over the holes (both ends) to keep bugs from moving up/in and setting up residences. The trick with the bread is that it keeps the concrete out of the tube and is extremely easy to clean out later. I had used wood blocks for my ash slot form void and spent about 2 hours trying to remove the swollen wood after the slab had set.

David's ideas will work great and may be simpler...I just thought you'd like several options to consider. Hope all this makes sense and helps...good luck with your slab pour...don't forget to pound/tap the sides of the forms to release any air bubbles/voids and make the finish smooth(er)

[david s]

This is mine. I've been doing it this way for 10 years now and it seems to work pretty well. As the heat will drive any moisture away from it the hole releases any steam pressure and provides an exit. I don't think you need too many. I only use one although my ovens are small.
This reminds me of firing a new kiln (empty) very slowly for the first time, when at around 400 C internal water began dripping from a lower corner and forming a pool underneath the kiln approx 200 ml. This occurred because moisture being forced away from the heat condensed against the cooler outer sheeting running down to exit at the lowest corner. I was surprised this took so long to happen and at such a high temperature.