Hearth Design Philosophy

[Dino_Pizza]

Re: Hearth Design Philosophy

Your Welcome, Kyle: Glad it's helpful.
BTW: welcome to the forum. Enjoy the planning stag. I found it as much fun as building. Don't hesitate to ask any questions as you're going thru the various posts.

Also, in looking at my floor plan of what I did and cooking with it, the only thing I would do different is that my oven landing between the 2 arches where I show a 15" dimension, I would have liked it 1-2" shorter. If it was 2" shorter, and with my tall and angled flu-box transition above it, it still would have drawn air/smoke really well and people with shorter arms could access more of the oven.

Also, as you can see by my drawing 4-1/2 by 5 concrete cmu (Concrete Masonry Unit, 16" block) could be smaller if you did an igloo type dome and not need extra few inches for framing the 'house' over it. I also like the ovens others build with the concrete base at an angle (45deg) for slightly smaller footprint.

So many great ideas on this forum. Too bad we usually can build only 1 .

-Dino

[Kyle Dillehay]

Re: Hearth Design Philosophy

Those are great suggestions! I really like the smaller footprint idea. The less concrete to mix the better for my back!
It is so hard to decide on a design there are so many creative possibilities.

[smallholder123]

Re: Hearth Design Philosophy

thanks so much i came upon your post just in time i start the base next week and having seen your plans for spliting the storage has made me rethink ,i want two openings so the wood can be loaded at the back and have time to dry as some of the wood will no doubt be a little wet and can be unloaded at the front a lot dryer kind of rotating your wood stock thanks again

[Amac]

Re: Hearth Design Philosophy

Hi
Another newbie here - and what a great site - today I finished the hearth slab. Iused a 4.5" vermiculite cement mix 5'x5' approx on top of a 4" concrete slab, but I surrounded it by 6" of concrete (about 12" at the front) so that I would not be building on the vermiculite which has a kind of spongy feel and seems a bit fragile. The (36") oven will of course rest on the vermiculite
No stand since my garden is sloped which means no convenient wood storage, and also the oven floor will be a little lower than I would have preferred. I have tried posting on other threads but for some reason my posts are vanishing into thin air so this is somewhat of a test. I will post a photo later if this works
Aidan

[RobDodds]

Re: Hearth Design Philosophy

Going back to hearth design, if concrete layer is purely for support could it be replaced with concrete lintels, which have pre-stressed steel reinforcement topped by Hardibacker board. I think gaps of a foot between lintels would still be OK to support modular oven. Not everyone wants to be mixing 3-4" of concrete. Any thoughts anyone??

[azatty]

Re: Hearth Design Philosophy

It's all about the open span (distance between beams). You'd have to know the maximum load you can place on the backer board across the open span. My gut says you could probably get away with it in a modular design because you're working with larger pieces that will spread the load over larger areas. I wouldn't trust the design for a point load, though.

[RobDodds]

Re: Hearth Design Philosophy

Thanks - I think it would work - open span for my base is 1.1 metres so I reckon 4 lintels would only leave spans of 5-6" of Hardibacker (sorry to mix metric & imperial!). If it doesn't look to be enough I could always double up the Hardibacker and epoxy the boards together to make a constrained layer for strength. Planning to use a modular oven so probably less weight than a brick Pompeii.

[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.

[Dagored154]

Re: Hearth Design Philosophy

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

[percy]

Re: Hearth Design Philosophy

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

[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).

[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

[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 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

[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?