Question about oven opening and chimney

[rwiggim]

So I guess I am not much of a planner and built the structure over my oven before building the oven and now I am faced with a predicament. My oven floor is 74" from the roof of the structure and I remember reading somewhere that if a chimney is too long it can suffocate the fire in the oven. I think with code it needs to be 15" above the roof of the structure so with a 12" tall door my chimney would have to be at least 77" tall. Forgive my ignorance but if I did a really short chimney would the heat dissapate quickly enough (see pic below for how open the structure is) or could I put some sort of barrier up there to block the heat?


And my second question is about the oven opening. I got a response from someone the other day that regretted making there opening small to keep the heat in better but had a hard time reaching the sides of the oven with a peel. Can I flare the bricks for the opening (see pic 2) with the idea that it would provide greater access and also provide a seal, on the sides at least, when the door is put in place? I realize I would have to make my vent flare as well but I plan on casting one from concrete anyways.

Thanks so much.

If anyone is in the Prtland area and wants a very active sourdough starter let me know. I am more than happy to pass it along.

[christo]

I'll defer to the other experts on the list to your chimney height question, but as for flaring the opening of the oven, I did it and have no problem acesssing any of the oven!!!



If you go for an arched vent- I'd lay the bricks for the opening on flat (as you did in your pic) vs on edge. I ended up supporting the sides with concrete butressing (not shown in this pic) as I was afraid they would push out over time. -

if I did it over again I would not go with the arched vent - I'd pour one - that way there would be no forces transmitted to the walls to try to push them out..... It's a time saver to be able to pour the vent/lintel ahead of bulding the oven or in paralell with constuction.

Good luck - take your time and enjoy building the oven - I'm sad it's over for me!!

Christo

[wlively]

No problems with the chimney height. You will actually get better draw with a taller chimney.

As for the opening, that is what I did as well. Not as dramatic as your mock-up but it definitely does help to access. I also agree with Christo, if I were doing it again I would cast the entire opening/vent in one piece.

[dmun]

I vote yes on the flared opening:



I'm also building a two story chimney. In general, taller is better for draft. There was a reason those factories had huge chimneys: the huge natural draft let them run giant fires.



(Denver has some amazing brickwork)

The only reservation, is that a masonry chimney that tall will need independent support. My stack of refractory flue tiles sit on the oven, but the masonry surround is supported directly from the base slab. Not a problem if you are using insulated stainless units, much lighter.

[nissanneill]

rwiggim,
I fitted my spark arrester only the other day on top of 3 lengths of 8" flue, some 10' high and it draws a treat with no smoke what so ever venting through the front arched entrance. See

http://www.fornobravo.com/forum/f21/...html#post13310

the remainder of the oven construction and stainless vent is on:

http://www.fornobravo.com/forum/f21/...10-a-2119.html

make it as high as it neds to be.
I used a different philosophy for my vent and decided to go the way I did for simplicity, the ease and ability to fit down lights which shine into the oven .

Neill

[rwiggim]

Thanks for all the great info.
Does anyone have an idea of a proper concrete mix for casting the vent?

[wlively]

See here.

http://www.fornobravo.com/forum/f8/c...highlight=ks-4 (cast lintel question......)