Dome on Insulation or Concrete Base

[eirebuild]

Hi all,
I see from some of the builds here that some build the dome directly on the concrete base underneath and some build the dome on the insulation.
I'm planning on using calcium silicate and am wondering will it have the compressive strength to hold the dome. I'm planning a 42 inch dome so there would be quite alot of weight, wondering what people's thoughts are on this.
appreciate any help in advance.
Thanks

[Firebrick4]

You should have a concrete base, with insulation on top of the concrete base. That way, it will hold. 2inches is what most use regarding calcium silicate boards, any more to me seems like overkill but that’s up to you! definitely insulate the bottom, I used a 3:1 perlite mix (it should be atleast 5:1) and I regret not doing the boards. most heat leaves from the top and sides, but for making breads you want to keep heat for a long time. Goodluck!