Oven dome finished what comes next external vent arch or insulation

[Simonchelli]

I’ve finally finished my dome just wondering what step is next is it insulation or building the external arch for the vent and when building the external arch does anything go between the internal n external arch or can they just butt up together

[Gulf]

Yes. They can just butt together. There are many examples of “heartbreaks” on the forum. They are subject of debate as to their effectiveness. It’s entirely up to you.

I am a little more concerned about the amount, type, and method of installation of your under floor insulation?

[david s]

If the flue gallery bricks just butt up against the inner and outer arches, unfortunately you are left with vertical joints that line up. This is asking for failure at those points because it introduces a structural weakness, the problem is exacerbated by the thermal cycling and its expansion and contraction issues. Just as a brick corner should tie the bricks together rather than a butt joint, so should the bricks in the flue gallery. This is much harder to do with brick units. Having said that many builds have been done by butting the bricks against the arches and they seem to be holding up ok. Personally I prefer a cast approach which allows a much thinner, lighter and shallower result.

https://community.fornobravo.com/for...723#post435723

[Simonchelli]

For the floor insulation I used calcium silicate board it’s 25mm we don’t have 50mm in Adelaide then I used 50mm firebricks On top of that

[Simonchelli]

So what are my options other then to butt right up

[david s]

So what are my options other then to butt right up

I've given you my solution (check the link), but if you are set on creating it in brick, check out the many builds on the forum.

Regarding the underfloor insulation, the calcium silicate board is excellent but extremely hygroscopic. I'm installing a very large 1600mm internal diameter oven currently and we've put down 80mm (two layers of 40mm) cal sit board. To prevent moisture wicking up from the week old concrete slab, I sealed it first. I also conducted absorption tests on some scrap pieces. After a 5 sec dunk test the piece doubled in weight and after a 3hr immersion it doubled again, resulting in 4 X its original dry weight. You must make sure, if the oven is out in the weather, that rain running off the dome does not find its way into the cal sil board. If it does then not only will it not insulate, but will be extremely difficult to dry out. Instead of having the supporting slab flat, I slope down the corners slightly to encourage water to run off rather than sit against the base of the dome. Sometimes a crack will develop there which allows water entry. The use of weep holes through the supporting slab near the centre also assist in the removal of water. Don't freak out, your oven will work ok, and Adelaide is pretty hot and dry, but inadequate or damp under floor insulation is the leading cause of floor temperature drop off. You can just move the active fire from side to side to recharge the floor when cooking pizza and for retained heat baking or roasting, just be aware that you are losing heat to the concrete below.

[Simonchelli]

Thank you I will eventually get the oven undercover as I heard the calcium board can act like a sponge I appreciate all the tips and advice as This is my first attempt at building a oven

[fox]

You dome looks nice and neat from what I can see from the single picture, but 25mm of insulation under the floor will not be very efective and a lot of heat will be transferred to the large base.
if you have laid the bricks inside the dome, then you could lift them up and add at least one more layer of insulatsion.

[Simonchelli]

Unfortunately I layed them ontop of floor so no way of lifting it looks like I’ll have to wear it I did think about doubling it up but it’s so expensive in Adelaide and hard to get

[fox]

Well yes it would be a big decision !
The oven should still work OK but it will take a lot longer for the cooking floor to get up the temperature and a lot quicker to cool down.

[Adelaide_Oven]

Your dome looks good, well done! Out of interest where did you source your board? I'm in Adelaide and looking for board right now.

[NCMan]

I actually prefer butting the bricks at that location. It's a perfect spot for a much needed control joint and I simply caulk it w/the appropriate high temp sealant. I look at the oven and external arch as two different structures. They need to be able to move a bit, given the extreme temps and conditions they can/will be subjected to. Having them slightly separated allows for this slight movement and tying them together can restrict that. Just my 2¢.

[Simonchelli]

I got the board from tuff and sons Richmond mate