Hearth Design Philosophy

[Xabia Jim]

Re: Hearth Design Philosophy

The dome-on-floor method is easier, using few or no cuts, and it's what I did.

Picture your finished oven as one unit, not a separate floor and a dome.

Opt for easier, no one except you will know the difference when it's finished.

[dmun]

Re: Hearth Design Philosophy

Quick question about the oven floor. Do you sit the walls of the dome onto the cooking floor or do you cut the floor round like Hendo did and have the walls rest on the FB or vermiculite concrete? It seems to me that the oven would be more efficient if the dome walls sat on the insulating layer and not directly on the cooking floor.

Either way works fine. The dome-on-floor method is easier, using few or no cuts, and it's what I did. The cut-to-fit method is what's used for professional ovens in constant use, where they may need to replace a worn or chipped floor in a few years. I figure any worn brick will be in the center, not the edge and can be sucked out with a shop-vac, and replaced.

I think the efficiency is the same either way. Both methods allow you to completely surround your oven with insulation.

[kgmfq3]

Re: Hearth Design Philosophy

Quick question about the oven floor. Do you sit the walls of the dome onto the cooking floor or do you cut the floor round like Hendo did and have the walls rest on the FB or vermiculite concrete? It seems to me that the oven would be more efficient if the dome walls sat on the insulating layer and not directly on the cooking floor.

Jay

[bbell]

Re: Hearth Design Philosophy

Dino, James and Christo,

My thanks toeac of you for the reply. Now waiting for a change in weather (above 32 deg. would be nice) so I can pour a slab.

Be well.
Bill

[Dino_Pizza]

Re: Hearth Design Philosophy

bbell,
That is exactly how I will be doing mine next month. If you look at Christo's answer above, and click on his link to his second page on his thread, (message #12? or something) you can clearly see a picture of his 5 blocks high stand, a 4" or so pour of concrete on that and then the 2" FB board or insulation board product that the oven floor bricks sit on.
Have fun on the project!
-Dino.

[james]

Re: Hearth Design Philosophy

That sounds right to me. The structural concrete slab at the bottom, either 2" of FB Board or 4" of vermiculite concrete on top of that, and the cooking floor directly on top of that.

We have a good base of experience that 2" of FB Board will readily insulate a residential oven and you will retain all the heat in your oven and the bottom of the concrete won't even get warm.

Go for it.
James

[christo]

Re: Hearth Design Philosophy

That's how I did it and it works great for me!

Christo

[bbell]

Re: Hearth Design Philosophy

Sooooo.... For the hearth insulation would you say that one layer of InSol Board, on top of the supporting slab, should be sufficient and skip the vermiculite cement all together?

Thanks

[james]

Re: Hearth Design Philosophy

I have an ash dump on both of my Healdburg ovens, and never use them. The also can get in the way when you are doing fire in the oven cooking -- as opposed to retained heat baking.

They take some effort to install, so on the whole, we recommend that you don't need one.
James

[Hendo]

Re: Hearth Design Philosophy

I have included an ash slot with an ash pit below, but can't yet comment on its usefulness or whether it gets in the way etc. I thought it seemed like a good idea at the time, and figure I can always fill it in if it proves cumbersome. Difficult to do it the other way around ....

My landing will extend some 12" in front of the slot when finished.

[RTflorida]

Re: Hearth Design Philosophy

I didn't put one in, can't say how useful it might be. I do know that ash removal is not an issue if you have a brush and shovel.
I have seen mention that an ash slot can actually get in the way when loading pizzas or other baked/roasted goodies.....having done all of the above, I can see how it might get in the way...excluding pizza, I tend to sit everything on my landing when loading and unloading.

RT

[bolex16mm]

Re: Hearth Design Philosophy

I am getting ready to pour the hearth but before I do, I have a question. Is it necessary to have an ash slot? I noticed on some of the other designs that they do but this design does not. Thanks

[Unofornaio]

Re: Hearth Design Philosophy

Concrete pre mixed from United Rental ? 5 sack.

In my experience this stuff from the rental yards is usually crap at best. But it is a VERY GOOD solution to mixing by hand and I would recommend it. What I suggest is for those of you that get the "spin buggy" the little tow-able spinning mixer, the day before get a 94# bag of Portland and have it ready, after you get the mixer home spin it up (make it go faster) and add the whole bag a shovel full at a time (adjust water content if necessary).
The problem with most of the rental concrete is the base mix is usually lacking cement and its mostly pea gravel which is easier to finish but doesn't have the strength of a 3/4 mix. In addition there is usually A LOT of sand and not much rock which even with proper rebar makes the slab weaker than it should be. When we pump a pea-gravel mix we always use 6 sack the extra cement makes up for the rock and the higher water content.
Checking the yards dry base mix (sand and gravel) ahead of time is also a good thing to do if its mostly sand thats what you are gonna get. Like wise you can also add a couple of bags (or more if its that bad) of rock into the mixer and mix it up. This is all much less hassle than saying "its crap I'm gonna mix it my self"...
Les- I'm not saying thats what your issue was I just thought Id add this advice in this thread. Ive had that happen to me as recently as 2 months ago. We did a patio for a lady and where the rebar was it was going off like crazy no idea course redi-mix is so bad now who knows what was reacting with what.it worked out though cause it was colored and when we troweled in the color it all went fine...very scary though to see that

[CanuckJim]

Re: Hearth Design Philosophy

Les,

Sounds like the cracks were hairline and superficial. This sometimes happens, depending on humidity levels during the mix and the pour. I think you'll be fine. Good job on keeping it wet.

Cheers,
Jim

[Les]

Re: Hearth Design Philosophy

Thanks Jim,

I sprayed it down immediately and covered it with tarps. Prior to covering, I took a rag and smoothed out the cracks so I could keep an eye on their progress. As near as I can tell they have not reappeared (as of yesterday). I bought the concrete pre mixed from United Rental ? 5 sack. I filled most of my cores using my mixer ? that?s why I decided to take the easy way on the hearth pour.

Thanks again,

Les...