Need help with my next steps.

[Omaharosario]

Just Finished the the stand and the have poured a 4" reinforced concrete slab for the 1st layer of my floor.
What to do next? Please give me your input on the best way to finish the next couple of pours before our dome. Thanks!

[Neil2]

1. Keep it continuously damp and covered for at least 7 days.

What type of under hearth insulation are you planning for ?

[Faith In Virginia]

Your next layer is either the Portland/ Vermiculite or insulation board. So insulation is the next step.

[Neil2]

Next, examine your new structural slab closely. Patch any voids in the top and sides.

The slab should also drain freely - no standing water. If necessary, grind the surface so as to eliminate or drain any low spots. Water will get into your oven from time to time so you should plan for it. If there is any "bathtub" it will be difficult and time consuming to dry out.

Layout on the slab the footprint of your oven and entryway. Allow for the brick thickness and for the thickness of the dome insulation.

If going the Portland/vermiculite route, form up on the slab for this shape. (You can use the existing form work to attach blocks to support the form work for the insulation layer). The shape does not need to be exact and can be a bit wider, however the insulation layer should not extend out to the edge of the structural slab, if it does this will be an entry route for moisture in the future.

You should keep your new structural slab continuous moist during the forming and pouring of the insulation layer. The insulation layer in turn should be kept moist for at least 7 days.

If going the insulation board route you need to have a flat surface under the oven footprint (still draining) to support the board. Leveling can be done with a thin layer of sand. Place your insulation board and continue.

[Omaharosario]

Under the hearth for the footprint we plan on using a type of refractory insulating cement.
Not to sure if one is better then the other or the price difference. Any thoughts?

[Neil2]

"a type of refractory insulating cement"

Not sure what this might be. Most builders here have either used a vermiculite (or perlite) / Portland cement mix of 5:1 or have used insulating board.

If using the vermiculite / cement material a thickness of 4 inches is recommended.

[RTflorida]

Sounds to me as if someone has not thoroughly read the Pompeii oven plans. If you have not, NOW is the time. You are at the point where using an ill suited material can make the difference in owning a fantastic cooking vessel or simply a tool for adding to global deforestation (you will burn a huge amount of wood and never hold the temps that you want).

You next step should be one of three options and nothing else:
1) 5:1 vermiculite/portland cement mix (4" thick)
2) 5:1 perlite/portland cement mix (4" thick)
3) Minimum 2" of refractory insulating board. Many manufacturers and various compositions, available in the Forno Bravo store if you can't find a local supplier.

RT

[dmun]

We have repeated problems with wet pre-mixes. They are made, as the man says, for boilers, where there are tiny, well fitted, joints, and they are completely isolated from any dampness. If your firing chamber doesn't reach those temperatures, the mortar never sets, and remains water soluble. If you must use a commercial refractory mortar, use a dry mix used for fireplaces, such as heat-stop50 or equivalent.

[Omaharosario]

Thamk you this is very helpful

Originally Posted by dmun

We have repeated problems with wet pre-mixes. They are made, as the man says, for boilers, where there are tiny, well fitted, joints, and they are completely isolated from any dampness. If your firing chamber doesn't reach those temperatures, the mortar never sets, and remains water soluble. If you must use a commercial refractory mortar, use a dry mix used for fireplaces, such as heat-stop50 or equivalent.

[Omaharosario]

My local supplier at "The Plibrico Company" suggested I use his product which is a pre mixed refractory cement that he uses for boilers that reach in excess of 2000 degrees if I am not mistaken. As far as not reading the Pompeii directions what part would you be referring to? Because I am just trying to use everyone else's experience along with the Pompeii directions to have the best knowledge in going forward with my project.

Originally Posted by RTflorida

Sounds to me as if someone has not thoroughly read the Pompeii oven plans. If you have not, NOW is the time. You are at the point where using an ill suited material can make the difference in owning a fantastic cooking vessel or simply a tool for adding to global deforestation (you will burn a huge amount of wood and never hold the temps that you want).

You next step should be one of three options and nothing else:
1) 5:1 vermiculite/portland cement mix (4" thick)
2) 5:1 perlite/portland cement mix (4" thick)
3) Minimum 2" of refractory insulating board. Many manufacturers and various compositions, available in the Forno Bravo store if you can't find a local supplier.

RT