Hearth Design Philosophy

[narcosi]

Re: Hearth Design Philosophy

Here is a drawing of what I did on mine:
It's a 42" oven, the concrete block base I did is 6 1/2' feet deep by about 6' wide. The width seemed about right for any 42" oven using glass fiber insulation (I used 3 layers of 'FB blanket') and I have a steel framed structure beyond that. I imagine if you do an igloo style (stucco or rendered exterior) it would be about the same.

I also have a row of concrete block thru the middle of the base stand to cut the 'wood' storage under it in half. This whole design of mine may have little to do with your design but I hope the oven dimensions help you out.



this is what it looks like:

Great post and diagram - thanks
I dont see a thermal break in your oven floor into your vent space - is this ok? struggling with the whole thermal break thing
it does look from your diagram that you planned one in the walls - or am i miss reading it?

loads more questions here: https://community.fornobravo.com/for...-oven-build-uk

thanks

J

[narcosi]

Wow - this is a really useful thread, thanks everyone who has posted.

My plan is: https://community.fornobravo.com/for...-oven-build-uk

100mm (4") reinforced base
50mm (2") FB (should i double this???)
I too was planning fire bricks on their side for extra mass (is this a waste?)
I will then be building the brick walls on the FB

Just read about leaving a small gap around the floor and not setting floor bricks - thanks (wont this fill with ash etc? / do you clean it?)
I assume the walls however are fully set with oven cement?

I have a few questions on my thread which i am looking for advice on so please have a look for me.

with a plan for staight side walls would you use blanket down to your FB base of even do vertical FB up the sides?

thanks all!

[narcosi]

Re: Hearth Design Philosophy

Hi AT,

Thanks for the info. Maybe I am using different terminology, being from the UK and all that.....I have attached a quick diagram of my proposed construction - please excuse lack of scale or detail as I am still earning SketchUp for this project....



I hope this all makes sense. The "Thermalite" blocks are lightweight, insulating concrete blocks that are very common here. The Ceramic Fibre insulating board is what I think you all call "FB Board". Damp proofing membrane is a polythene sheet that will go under the base slab itself - I would also use another layer of DPM after the first ocurse of concrete blocks in the support walls.

Cheers,

Alasdair

Did you ever build this?

Im just starting out in the UK and have created this topic where i could do with advice: https://community.fornobravo.com/for...-oven-build-uk

thanks

[Aquaponicsguru]

Re: Hearth Design Philosophy

I have seen glass bottles with perlite/vermiculite used for cob type pizza ovens. Anyone have any opinions on using glass bottles with a p/vcrete mix?

[Georgel]

Re: Hearth Design Philosophy

Door shape: Is there and advantage of the rounded doors? My house has straight lines and I am thinking of a rectangle door. Is this going to be a problem? 47 inch oven with16 inch dome height and 10 inch high by 20 inch door.

[C5dad]

Re: Hearth Design Philosophy

Someone has said have the floor 'floating' what exactly does that mean? I was intending to bed mine down using a quite wet mix of homebrew
( i intend to have my floor inside the soldier first chain).

A floating floor is free to move with heating and cooling. Please do not bed your bricks and make sure there is a gap between the floor and dome (about the thickness of corrugated cardboard) to allow expansion of the floor outward without damaging the dome.

[C5dad]

Re: Hearth Design Philosophy

Hi,

Looking to get some advice on the Hearth design in particular the insulation medium. I have purchased Vermiculite to blend at the suggested ratio of 5:1 with portland cement. Is the insulation cement strong enough to place the floor and dome directly on top of or is there an extra layer required to provide stiffness?

Yes, it is more than strong enough to support your dome. You do not want your dome on up insulated material as the heat will get "sucked" out -that is a highly technical term ya know.

Chris

[Cappa]

Re: Hearth Design Philosophy

Hi,

Looking to get some advice on the Hearth design in particular the insulation medium. I have purchased Vermiculite to blend at the suggested ratio of 5:1 with portland cement. Is the insulation cement strong enough to place the floor and dome directly on top of or is there an extra layer required to provide stiffness?

[adm]

Re: Hearth Design Philosophy

Hi AT,

Thanks for the info. Maybe I am using different terminology, being from the UK and all that.....I have attached a quick diagram of my proposed construction - please excuse lack of scale or detail as I am still earning SketchUp for this project....



I hope this all makes sense. The "Thermalite" blocks are lightweight, insulating concrete blocks that are very common here. The Ceramic Fibre insulating board is what I think you all call "FB Board". Damp proofing membrane is a polythene sheet that will go under the base slab itself - I would also use another layer of DPM after the first ocurse of concrete blocks in the support walls.

Cheers,

Alasdair

[ATK406]

Re: Hearth Design Philosophy

Hi All,

For the ceramic board - should that be cut to the same dimensions as the inside of the hearth itself with only the firebrick hearth on top of it, or should it cover the entire base of the oven with the dome itself also bearing on it? .....

Anyway, as you can see I am still at early planning stages but would welcome any advice!

Definitely insulate your dome walls from your support slab. It sounds like you are planning to use lots of insulation and that is a good thing. I must admit I'm a little confused by your description of the many layers of your slab/insulation/hearth floor. Have you sketched this out? Maybe a simple diagram of your plans and the associated materials would clear things up.

AT

[adm]

Re: Hearth Design Philosophy

Hi All,

First post....so be gentle! I am in the UK....so metric dimensions I'm afraid!

I am still at very early planning stage, currently deliberating between modular and brick built oven. I am leaning heavily toward full brick build though and am planning around that....

I am currently trying to draw out my base and hearth, so could do with some advice....

The base itself will be on a poured slab reinforced with rebar. I will put membrane down under the slab. Walls will be concrete block filled with concrete and rebar.

On top of that, I will pour another slab for the base of the hearth. I am thinking of making this 100 or 150mm thick, then laying a course of thermalite blocks on their side on top of that. On top of those, I would put 50mm of the ceramic fire block board and then finally on top of that the firebrick for the hearth itself. I am leaning towards having the firebricks on their side as opposed to flat to get some extra thermal mass.

So - does that sound about right? Or am I missing some vital ingredient? I see lots of vermicrete used in bases, but if I use thermalite blocks, the ceramic board and firebricks on edge, do I need it?

I like the idea of having the firebrick hearth cut to fit inside the oven dome, with a soldier course of firebricks around the outside rather than have the dome bearing on the firebrick floor....which gives me another question:

For the ceramic board - should that be cut to the same dimensions as the inside of the hearth itself with only the firebrick hearth on top of it, or should it cover the entire base of the oven with the dome itself also bearing on it? I am not sure how strong this stuff is in terms of compression and there would be a lot of loading on it from the dome.

Anyway, as you can see I am still at early planning stages but would welcome any advice!

Thanks,

Alasdair

[h12rpo]

Re: Hearth Design Philosophy

Someone has said have the floor 'floating' what exactly does that mean? I was intending to bed mine down using a quite wet mix of homebrew
( i intend to have my floor inside the soldier first chain).

[percy]

Re: Hearth Design Philosophy

dino thank for the drawing. it gave me more ideas and you made my project easier. thank you. Percy

[Dagored154]

Re: Hearth Design Philosophy

I would put more lintels in to reduce the gaps and it should work.

[Dagored154]

Re: Hearth Design Philosophy

In speaking with a local hardscape builder who has built many ovens he has recommended that I put splits on the cooking surface. if the cooking surface gets damaged or worn out I can then easily replace them. it seems plausible, what do you all think? How do you actually replace bricks inside the oven ten years later? that would seem impossible to do.