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mmmhumous 03-30-2008 12:33 PM

Help Please - about to start work!!
 
3 Attachment(s)
Hi Everyone,

Just about to start work on my oven (already built a base for it and bought some firebricks). I've been reading some of the threads on the site and found them really useful!

I Just had a last few questions:

For info: I'm using red bick (engineering grade B) for everything except the hearth for which I've got firebricks. I'm using an arched roof rather than a dome and plan to have a tiled roof for the external wall (aiming for a final finish similar to this oven: VillaGok brick oven) and up to now have been using blue cirle mortar (1:1:6 cement:lime:sand). In terms of use, the oven will probably get 1-5 firings per month. I've attached (hopefully) some shots of the base and a quick mockup.

Questions

1)wrt to the hearth: I plan to lay the 1st coarse of the extermal wall and use this in place of a form, for a 1-2 inch/ 50mm thick layer of 1:5 cement/vermiculite. Once set I was going to lay the firebricks on builder's/sharp sand on top of this insulation layer. will this be sufficient?

2) I'd like to just use the blue circle mortar for the main part of the oven as well. As it's got some lime in there will it be good enough (given my choice of brick)?

3) For the insulation on/around the oven, is loose vermiculite good enough or do I need the cement/vermiculite layer ass well?

Any thoughts are very much appreciated.

Cheers!!!

Dutchoven 03-30-2008 05:08 PM

Re: Help Please - about to start work!!
 
Hi mmmhumous,


For info: I'm using red bick (engineering grade B) for everything except the hearth...I am concerned here because your bricks are not solid bricks and I am not sure how they will hold up for you...
I'm using an arched roof rather than a dome and plan to have a tiled roof for the external wall...your planned design should work well
and up to now have been using blue cirle mortar (1:1:6 cement:lime:sand)....you should probably include 1 part fireclay into the mortar mix
Questions

1)wrt to the hearth: I plan to lay the 1st coarse of the extermal wall and use this in place of a form, for a 1-2 inch/ 50mm thick layer of 1:5 cement/vermiculite. Once set I was going to lay the firebricks on builder's/sharp sand on top of this insulation layer. will this be sufficient?...more insulation would be more efficient...most builders here on the forum to the best of my recollection used 2 inches if it was the calcium silicate sheet and at least 4 inches if it was the vermicrete
2) I'd like to just use the blue circle mortar for the main part of the oven as well. As it's got some lime in there will it be good enough (given my choice of brick)?...as I said above you should think about adding some fireclay

3) For the insulation on/around the oven, is loose vermiculite good enough or do I need the cement/vermiculite layer ass well?...loose vermiculite is good as an insulator but might want to coat the oven with a 1 inch thick layer of refractory cement to give the oven a bit more strength...the barrel vaulted oven like you are planning thrusts on the side walls...

Hope this helps!
Dutch

Acoma 03-30-2008 05:10 PM

Re: Help Please - about to start work!!
 
What is funny is that I look at these photos and immediately think of RC and the split front storage area. I see that you want to use this more for breads than pizzas. This appears to be a bread oven, and we have numerouse experts on this.

As for insulation, you definately want some blanket at 3"+ over the brick. Then it depends on each use. You say 1-5 per month, so is this a second home or are you kidding? You will use this so much more than you realize once you get the foods going. Answer this question before you get better advice on insulation since the character of insulation density determines resultes per usage. Trust me, it goes far.

Acoma 03-30-2008 05:11 PM

Re: Help Please - about to start work!!
 
Wow! I guess Dutch was on the thread with ideas at the same time. Thanks Dutch.

dmun 03-30-2008 05:14 PM

Re: Help Please - about to start work!!
 
Two inches (50 mm) is not enough vermiculite! Four inches underneath! If you need, like me, to keep your under-oven thin because of design considerations, you need to use cal-sil board or equivilant high tech refractory insulation board.

This is important! You will never get more than one chance to insulate under your oven. Sand will help level the bricks, but it has NO insulation value.

And, yes loose vermiculite is fine, if you build an enclosure to house it. You can block off the corners, to reduce the volume needed. Be sure your enclosure is tight if you use loose insulation, the powdery stuff can leak out of surprisingly small cracks.

Sorry to be emphatic, but I can't tell you how many builders have not asked this simple question before, rather than after, when their ovens are burning cords of wood and not reaching pizza temps.

gjbingham 03-30-2008 05:35 PM

Re: Help Please - about to start work!!
 
I'd defer to Canuk Jim and Dutch. He and Dutch are the barrel vault oven masters here. (please excuse me if I've forgotten others).

I'm not one hunddred percent sure I understand your meaning, but I'm thinking though that it might be a bad idea to place the walls external to the floor, simply because the expansion of the floor bricks as the oven heats might break your mortar joints at the base of the wall. Just a guess.

Listen to dmun carefully. He speaks great truths.

Frances 03-31-2008 01:40 AM

Re: Help Please - about to start work!!
 
Quote:

Originally Posted by Acoma (Post 27977)
. You say 1-5 per month, so is this a second home or are you kidding? You will use this so much more than you realize once you get the foods going.

Listen to the people and be glad you asked for advice before it was too late.

Well, all appart from Acoma... just kidding ;) - what I really wanted to say is that while I consider that I use my oven a lot, it usually comes down to one firing a week maximum, although the heat then lasts for three days. So I think the 1-5 firings a month could turn out to be a very realistic estimate.

Acoma 03-31-2008 10:09 AM

Re: Help Please - about to start work!!
 
Frances, your right. I will do 5+ per month now, but the heat keeps going, and so the use keeps going. My wife says, no need for indoor oven this summer. How funny.

mmmhumous 03-31-2008 10:46 AM

Re: Help Please - about to start work!!
 
Thanks a lot guys for your quick responses and messages. They’ve been very useful!! I’ll beef up things on the insulation front: to 4-5inches below the hearth (whatever 2 courses of bricks works out to) and add a vermicucrete layer on top before I add the loose stuff.

Unfortunately, the project’s financial director (my wife) has informed me I’m stuck the engineering bricks (bought a pallet of them), but I’ll add some fireclay to the mortar mix for the main part of the oven if I can find a supplier (Travisperkins don't seem to have any in stock anywhere near manchester)..

GJBingham - Just to clarify the design: the oven walls will be on top of the firebrick hearth. (it’s the bricks for the enclosure wall that won’t be and there should be gap of 50mm or so on each side to allow for expansion of the hearth).
In terms use, I was mainly planning to use it at weekends when we have the time and occcasionally when we have friends over during the week. But I guess it depends on the results, we might end up doing most of our roasting in there

Acoma 03-31-2008 12:17 PM

Re: Help Please - about to start work!!
 
INSULATE all over. Sounds like you will use it a lot. You WILL want that retained heat.


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