Help pls laid concrete base what's next?

[This lass builds UK]

Hi all 1st time trying to build a dome WFO based in the UK. Cooking floor 76 cm diameter. Have laid concrete base. What's next, a few questions:
1. Should I do:
a. Concrete base, CFB insulation, fireclay/sand (50/50 mix), firebrick
b.Concrete base, fireproof adhesive, CFB/ firebrick
c. Concrete base, upturned mosaic tiles, CFB, firebrick, sand if needed under fire brick
D. Something else

2. Do I need weep holes on my concrete base , how do I make them, what the heck are they? Do they go between the concrete base and the CFB.

3. How to I avoid the CFB getting wet? Don't want floor firebricks to end up uneven in time from moisture.

4. Should I put the 1st course of the dome around the oven floor onto the concrete or should I put CFB under the first course of dome bricks too? If 1st course on CFB how do I stop water getting into the exposed CFB rim under the 1st dome course? Could I use home brew ( sand/lime/cement/fireclay) to paste around the rim before the fire blacker etc cover it. Need to make sure water doesn't get in when building the dome.

5. Do I put 1st course fire brick around CFB and oven floor which will ensure CFB isn't exposed

6. Can I use home brew as a mortar on the outer part of the dome where the gaps between the bricks are bigger or do I need special fire cement / fire mortar which is much more expensive. Going to use vitcas fire cement on any small gaps in the touching inner bricks.

Many many thanks in advance on helping a lass build in London.

[NCMan]

Hi and welcome!! Can you post a photo of what you have so far?

[This lass builds UK]

Here a photo of the base. I'm tempted now to put a dusting of fire clay and sand although the base is level so possibly doesn't need it, then ceramic fibre board then a layer of sand and fireclay dry mix them my oven floor.

The other photo is just laying out however I then got worried about exposing the CFB to moisture and then cut my floor bricks so they went inside the first ring of the dome rather than the first ring starting on the floor which in hindsight is already a mistake but can't come back from it.

I think my pertinent question is will mortar on the bottom of the first line of dome bricks (which sit next to the oven floor and on the ceramic fiber board) be a problem as I'm worried the mortar will soak into the board?

Many many thanks for any advice!

[fox]

I always sit the dome on top of the floor bricks to allow for expansion of the dome.
Ceramic fibre board is very dense and possibly a lot more durable than you seem to think.
If your slab is level you dont need to bed the board or bed the bricks on to the board.
If the board does get damp it will not effect it very much from a structural point but it will effect its insulating properties however you want to avoid soaking the board or have it sitting in water.
During every aspect of your build you must consider how best to keep the insulation dry, drilling some holes in the slab would allow any water to drain away from under the board but far better to avoid any water getting under the board in the first place!

[This lass builds UK]

fox really appreciate the response, hoping the CFB will live up to expectations. I've already chopped the floor bricks which means the dome will now have to sit on the outside of the floor bricks bit still on the CFB.

Do you know if I would need to put mortar between the CFB and the first line of the dome or would the weight of subsequent dome bricks hold it in place?

Cheers

[fox]

You can lay your first layer on top of the board without any mort or you can bed them if you wish.
You will have to be very careful fitting the floor inside the dome, the floor bricks need to be laid to allow for movement.
The bricks will expand when hot and contract while cooling so you can’t bed them down of fix them together, you must leave room for expansion or the bricks will force the dome to crack.
That is why it is better to sit the dome on top but it is certainly possible to fit the bricks inside as long as you leave a gap for expansion.

[SableSprings]

As fox noted above, many people lay their dome on top of the cooking floor simply to avoid cutting out a "round" cooking floor perimeter. When laying the dome around the cooking floor, putting pieces of cardboard between the floor and the dome base perimeter leaves enough expansion room when it burns out and space(s) are quickly filled with ash. In my opinion, the best practice to keep moisture from your base insulation is your option C in the initial post. I've attached a link to a thread that has a great illustration of the "best practice" oven base layering. The weep holes are definitely worth doing just to allow any moisture that might accumulate under the oven an escape route. (We also recommend attaching some insect screen on the outer side of the weep holes to keep insects & other critters from making a home...)

You can use just plain old home brew mortar to fill the gaps between the outer dome bricks. Many of the premade "buckets" of fire mortar require much more heat to set properly than the outer oven bricks will experience.

https://community.fornobravo.com/for...andpoint-idaho

Asking questions and considering options tells me that you will be successful in this project...looking forward to your build