Floating the Hearth

[RDL]

I have purchased a Premio2G100 kit, and have completed the slab and the concrete block stand. My question is should I float the hearth by using the full coverage of the concrete blocks with the 1/2 inch Backer Board, or can I omit the Backer Board and fill the unfilled concrete block chambers with concrete and rebar when I pour the hearth? I believe this will make a more structurally strong unit, but I don't want to create heat transfer problems from the hearth to the stand, resulting in long term structural damage. I have read and received mixed opinions and responses to this question. I am stopped on my construction until I resolve this issue.

Thank you,
RDL - Woodlands, Tx

[NCMan]

Re: Floating the Hearth

RDL......if you have read and received mixed opinions and responses, you are likely to continue to get them by asking on here, I would guess. If you properly insulate in between your slab and your oven, there should not be much, if any, heat transfer to worry about. There are many builds on here to study that can be quite helpful. Personally, I prefer a floating slab w/a bond break. My 2?.

[RDL]

Re: Floating the Hearth

NCMan-
Thank you for your input. I agree with you on "floating" the hearth to achieve that heat transfer barrier, and I now believe that if the stand is well constructed with the concrete block chambers filled with concrete and rebar, the weight of the hearth and oven will provide a structurally solid unit. I will keep you posted as I complete the project.
RDL

[Tonyp]

Re: Floating the Hearth

Based on your description RDL, I gather you have completed the block wall but have yet to put anything on top yet? Seems to be a little confusion about what comes next. From what I have seen most builders will pour a reinforced slab on top of the block that is tied in with rebar to the block wall. The cement backer board is slightly larger than the opening between the block and supported from below during the concrete pour.

Once that is completed you then put down your insulation layer. Simply 'floating' the hearth does not provide a heat transfer barrier. Next comes your oven hearth. The hearth and insulation layers have no structural integrity and must both sit on top of a structurally reinforced concrete slab or some other such support base.

[Greenman]

Re: Floating the Hearth

Hey RDL - Tony has it right. The FB plans are clear about the supporting slab being required. The 'floating' of the oven refers to having it totally insulated from the base and the dome being insulated to retain the heat in the oven unit. The base and the structural slab hold it all up.

Good luck with your build.

[NCMan]

Re: Floating the Hearth

RDL....I think you may be using the wrong terminology at times and possibly confusing people. Not sure if that's the case or not. Photos always help. There is however, no need to tie your support/hearth slab into your block w/rebar, etc. as it gives no real advantage. It's simply a way some builders choose to do it. When a slab is poured and not tied into the foundation w/rebar, then it's called a floating slab, not a floating hearth, as they are two totally different things. If tying it in w/the rebar is the way you choose to do it, it will work just fine. Either way works. It's your choice. Best of luck to you.

[RDL]

Re: Floating the Hearth

Greenman-

Thanks for your response. As I originally noted, I believe I've read too many web sites. You have reinforced the terminology of a structural hearth and an insulation hearth, to which the various web sites associate vermiculite, if I understand your point, the 3 inch Forno Bravo FB Board is the insulation hearth. The hearth illustrated on page #25 of the FB Installation Manual is the structural hearth. Where I got crossways was with the illustration 3.3 on page #25 and illustration 3.4 on page #26 where they show the backer board covering the block cores in the stand. From there, I did not see the filling of the concrete block cores and the rebar ties between the stand and the structural hearth. I now through my paralysis by over analysis and will start on the stucyural hearth on Monday. Thanks

[RDL]

Re: Floating the Hearth

NCMan-
Thanks again. I believe I can go forward from here. I'll keep all of you posted with progress photos.

[NCMan]

Re: Floating the Hearth

NCMan-
Thanks again. I believe I can go forward from here. I'll keep all of you posted with progress photos.

You're welcome. I'm looking forward to following your Build.