40' in SLC various planning questions

[CapnJPants]

I started my work a few months ago. I just finished the construction work on my base and I'm finalizing plans for building my oven. As of now i'm planning on building a 40 inch oven. I have a few questions.

1) I'm planning on having 2 inches of ceramic fiber board insulation and 2 inches of fire blanket insulation. I thought this was enough but I've read some stuff recently saying that I should have 4 inches of each.
2) what do I use to adhere the fiber board to my concrete 'table top'?
3) I also read some place that you need to have a few wholes in your table top to let moisture out. How many are suggested?
4) What's the recommended diameter of chimney for an oven this big? I've been counting on 8 inches.

[JRPizza]

Nice looking base - looks like you are doing a corner build?
I would encourage you to use more insulation, especially if you want to do any retained heat cooking. I ended up with 5" of board in the floor, but that is because I got a better price on 2.5 inch board and did 2 layers. Built mine at 39" as the brick OD for a 39 comes out to be 48" which allowed me to maximize the footprint of my board. I have 3" of blanket but probably would go thicker if I built again.
I didn't adhere my board to the hearth as with a ton of bricks holding it down the boards aren't going anywhere. Some use a sand mixture to level the board out buy mine was flat and constant thickness so I didn't need any.
Can't help you on weep holes as I didn't use any. I figured my roof would keep out water but it all got soaked during my build. Weep holes would have helped!
Lastly 8" pipe should be fine for your oven size. I used 8 for my 39 and it draws very well, and the FB plans say 8" is good for a 42" oven.

[CapnJPants]

Thanks for the response. it's a corner design because I'm building prep area that will have a big-green-egg style bbq set inside.
For the insulation i'm mostly worried about safety. I'm also planning on doing a couple inches of perllite cement. That seems like a less expensive option as I'm already over budget on this project.

Thanks for the quick reply. I'll attach more pictures as I progress.