Hearth Design Philosophy

[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.

[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

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??

[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

[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

[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.

[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

This is a very useful diagram Dino, thanks for posting. I am in the plannning stages of designing my own oven, what a great forum this is! Kyle

[Dino_Pizza]

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:

[countryboy]

Re: Hearth Design Philosophy

What size oven are you building and what are the dimensions of the hearth? I.e., wondering how much weight you will put on the hearth and how far from the edges it will be...

[Dino_Pizza]

Re: Hearth Design Philosophy

Congratulations on starting! You're going to have great time building your oven and certainly using it when it's done.

Your hearth thickness: the 3"-4", is this just the concrete pour? Are you going to put 4" of vermiculite-concrete insulated mix on top of this or where going to use a rigid insulation board (1" or 2" glass-fiber board)?

Mine is 3.5" to 4" but I have a lot of steel rods in it too. You don't have earthquakes in the UK so you probably rarely use steel reinforcment in small things but...my opinion would be that I would have no problem with 3" if there was some steel in it. Since yours goes 3" to 4", I would think that would be fine.

By-the-way, all other opinions trump mine )-Cheers, Dino

[ja50ny0ung]

Re: Hearth Design Philosophy

Hi all, I'm all new to the forum, I?ve been researching and following this great site, my build is a few weeks in and I?m just about ready to poor my hearth. The question troubling me is that of the hearth thickness, the Bravo plans state 3.5" thick and some members insist on 4" minimum, the way my build has panned out my hearth is only 3" at the edges but recessed in the centre by 1" giving a total of 4" for the majority of it. Should this be ok??

Thanks

[chirobuggy]

Re: Hearth Design Philosophy

Thanks to all for this great knowledge base. I think I'm close to starting the journey.

[dmun]

Re: Hearth Design Philosophy

Your oven should be entirely surrounded with insulation. Having the board sticking out beyond the oven floor means less dome insulation that you would need to surround the unit than if you cut it exactly to fit under the dome.

[jhobbs]

Re: Hearth Design Philosophy

When using the FB for the insulating floor does it need to be as large as the support slab or just big enough to cover the oven floor, I imagine that you need some are to absorb and reflect the heat.