Wrong dimensions - Help!!

[peterthewolf]

Re: Wrong dimensions - Help!!

Lwood-

Great! Thank you for the simplified answer. This does make sense. In the interest of keeping the fix as easy and inexpensive as possible, do you think that there would be a problem going with the earlier idea of installing an "o-ring" of non-porous material like scrap iron, or for that matter, a ring of fiberboard donut two inches thick, to give that edge support against the potential cracking you drew, (instead of chipping a slot) into the brick wall all the way around the dome? Could we do this and accomplish the same result? I really do like the idea of fiberboard for the inches that it would save in resulting floor space, and saving that big chisel or mini jackhammer job is tantalizing.

Meanwhile, everyone is leaving out answers on the kiln shelf dome - lowering as a way to quickly eliminate the extra 8 inches up there for 63% door. Would you folks please comment on that?

Finally, that last question on the 3 inch difference between the door and the exhaust flue: if their heights were identical, with flue inside the door, does inside or outside the door really matter - when we consider that hot exhausted air goes up, and fresh comes in below along the floor? I'm not seeing the difference and would like to hear about this one. Now, there *is* another flue, *directly above* the outside of the door. It just doesn't descend as a pipe: it is open air up the door's outside wall, up to the structure's arch and out right there. So it does not "draw" - it is just air out the door and up on it's own. We *could* just use that and forget about that pretty (higher) pipe in the rear if we had to. But do we have to, or can we just keep it - lowered inside to the same 15 inches as the door? Remember, if we really need to just eliminate the inside flue altogether, that's as easy as putting a piece of sheet metal on top of the pipe, like I simply turned the meshed cap over on it's flat side before to seal the pipe; it does work...

You guys are spending an extraordinary amount of time to help, and I am very appreciative.

[Tenorio74]

Re: Wrong dimensions - Help!!

Hi Peter,

As Lwood said, you need the air space to avoid moisture getting in to your new slab. Just putting plastic down and laying it on top won't do it IMHO, too close at the sides.

The "shelf" concept is simple. I have attached a simple diagram to explain myself better. It works the same as when you make a concrete table or bench against a wall. It needs to BIND with something.... I don't know the proper architectural names in english, but I have explained as best I can.

Just the slab with rebar won't do it - even with rebar it could crack or shift or topple like a see-saw. Maybe an architect or engineer here on the forum could explain it better...

On the other issues, if you use vermiculite you don't need fiber board - BUT you will have to go +2", because I think it's 4" for vermiculite (I used CF board)... Check out my last diagram - you can see the air spaces where your old firebrick floor used to be...

If you go for this, then you can figure out how to solve the door (63%)...

[lwood]

Re: Wrong dimensions - Help!!

Peter, you need a an air space btw the old floor and the new floor so you don't get wicking of water into the new floor.

[peterthewolf]

Re: Wrong dimensions - Help!!

Tenorio- Thanks for your time and rethinking. How about these thoughts-
If I read it correctly, the only airspace added here was the ceramic fiberboard, sitting on the old vermiculite. Is that right? Or am I supposed to dig out that vermiculite and replace it with (which one or both- the new slab on top of the original one, then fiberboard on top of that before re-flooring)?

Are you saying that a new slab sitting on fiberboard, with a re-floor would do it? If we (did) use vermiclite, that's just a matter of putting it in a shovel at a time, or an hour longer of labor than dumping wheelbarrows of it. Put down some cardboard for protection and then pass it in through the door by the shovel ful. That's ok, but I do like this fiberboard idea. We'd just have to cut it in pieces and assemble the jigsaw puzzle onto the base once it's through the little door opening, max now on diagonal about 20 inches to fit it through

*Then*, again, the door is a mess to want to deal with. Some metal casing could easily drop those three inches of 18" flue height that is in the arch located just inside the 15 inch door to match the door height. That's a quick sheet metal thing; we could order it up and screw it onto the existing and forget about it. In that case, then at 15 inches, is it a problem if instead of smoke going *outside* the door before rising, that at the same door height, the smoke could go up from about 8 inches distance *inside* the door?

Again, thenn instead of building up the floor even higher, why not just lower the dome peak with that ceramic shelf?? We *will* call the shots, so if all of your folks thought is to not let him drill the dome hole, we won't bother with that.

Finally, about support at the walls: Why do we need to dig in at all? It's brick, the floor is flat and sits flat on slab already. I don't understand the concept of "shelf". Please educate me; I'm having trouble envisioning it as necessary. How we doing so far?

[peterthewolf]

Re: Wrong dimensions - Help!!

Tenorio- Thanks for your time and rethinking. How about these thoughts-
If I read correctly, the only airspace added here was the ceramic fiberboard, sitting on the old vermiculite. Is that right? Or am I supposed to dig out that vermiculite? It seems to me if I understood, that a new slab sitting on fiberboard, with a re-floor would do it in reading this? If we (did) use vermiclite, that's just a matter of putting it in a shovel at a time, or an hour longer than dumping wheelbarrows of it it. Pass it in through the door. That's ok, but I do like this fiberboard idea. We'd just have to cut it in pieces and assemble the jigsaw puzzle once through the little door opening, max now on diagonal about 22 inches. *Then*, again, the door is a mess to want to deal with. Some metal casing could easily drop those three inches of 18" flue height that is in the arch located just inside the 15 inch door to match the door height. That's a quick sheet metal thing. Again, then instead of building up the floor even higher, why not just lower the dome peak with the ceramic shelf?? We *will* call the shots, so if all of your folks thought is don't let him drill the dome hole, we won't bother with that. How we doing so far?

[Tenorio74]

Re: Wrong dimensions - Help!!

Hi Peter,

I guess any of us would have to be there and see your oven for real to see what could be done in reality... I'll summarise what I think and let others chime in their opinions.

Looking in to this more closely, I hate to say that the easiest thing would be a re-build. My first drawing didn't have the proper proportion width and confused me (and it was up late)... now seeing it properly, with your mountain style dome and very long tunnel door, I must say the re-build might be easier...

My other idea, expanded, is:

1. You must raise the floor to eliminate the moisture problem. This is the reason you can't get away with just lowering the dome (if your floor was ok then this would have done it alone). The new floor would dig into the walls otherwise it would have no support. You could dig 1.5" if you're worried about the walls collapsing straight down (highly unlikely I think). The new slab should be like a shelf resting on the walls.

2. You need to make a new slab with concrete. Just rebar wouldn't do it, and it bends quite easily under strain (fire bricks are quite heavy)... And if you used vermiculite again, how would you pour it??

3. For insulation you could use vermiculite or ceramic fiber board. You know the first. CFB doesn't have anything to do with moisture. The best way to describe it is pressed fiberglass made into a lightweight highly insulating board, with varying thicknesses. This can replace the vermiculite (at least 2").

4. Once you're done with the new floor (the hole you cut into the walls is now filled with concrete, so rest easy), you must alter the door opening to get proper height. You door is a tunnel, so this is the biggest challenge (the rest was easy). In effect, you would be tunneling a new door into your dome, which can be done, but would be quite the job.

In the end it looks a bit like a primavera oven.... It could work but the door issue would be a b*&^%!

[peterthewolf]

Re: Wrong dimensions - Help!!

Peter,
The first thing you need to do is adjust the resolution on your camera so you can post the pictures yourself. We need pictures with the explanation not three days later. Next, That mason has too much history with this project already. He will just be an interference. Get a new set of eyes on the project and deal with the old mason separately.

I told you the excavating would not be easy. You may even have to remove the exterior finish around the concrete oven slab, COMPLETELY. Get over the hope that you can do this without excavating everything underneath the oven, because you can't. I know you would like to preserve as mush as possible, but that whole front arch structure may have to come down in order to get to the slab. Get another mason to look at it and figure out how that can be done. Believe me, a knowledgeable mason will be able to do what I am proposing. You may not like what they have to tear down but it all can be re-done.

The 2" concrete slab gives me concern. I question whether or not it can structurally hold the weight of the oven as a suspended slab. 2" is not much concrete. But we will assume it will and proceed.

Get another mason to give you a quote on doing the excavation and we will proceed from there.

Lwood, RT and Tscarborough - just read yours out of sequence. Great advice - I will absolutely get a mason to come out and evaluate this. It may be Monday or Tuesday and I'll get back to you on that part.

Sorry about the pics; I've been sending them over Brickie to load who's been a sport.

...actually, no, while I have a number of talents, I'm clear that I'd not be able to build it myself - this kind of thing is just not my skill set. As Clint said..."a man's got to know his limitations"... Damn, that's why we hired this man when he said of all things he does, this goes so far back in his career that it would be nothing for him to build one...essentially that it makes him an expert as we heard it. Perhaps if (these) plans were really followed, we would have benefitted from that.

[peterthewolf]

Re: Wrong dimensions - Help!!

So, a few things. First, the door has an embedded metal lintel, so I think it ought to stay put as that's structural, and the door hinge is actually welded to a 3/4" pole that goes up into a pipe in the brick structure (sorry) that was a bit of an afterthought for the guy after it should have gone instead into a simple metal protruding ring at the front. That's what is under the double-bulging copper unit above the door. It's that structure that is up on the left behind the copper sheet, but I think in an earlier photo the copper wasn't there yet so you can see it. The right copper one is hollow but only bulging out there in design to mimic the left brick protrusion so it isn't ugly. The bottom of that hinge pole is buried around 8 to 10 inches below and swings inside a slightly wider pipe on a disc of stainless down there. So the door is likely a structural keeper at 15x15.

Next Q: I get it about the airspace. Cool. Would that 2" airspace replace the vermiculite below it essentially by breaking contact with it with a new slab? How about not another slab but just doing airspace with strong fiberboard with say, some rebar laid beneath it to give regularly space "ribbing" support like bed slats? Gosh, sorry, what is fiberboard exactly & does it have other names? I take it this is a non moisture conducting sheet medium that may heat up through the floor but not transfer it to a cold wet surface below - especially if air not contact is below it, right? I keep thinking that the joint area at floor meets dome base is least important of all. Could this be true?

Q: A little less height than 15" is ok for the door; we still can get a big bird or creature in there perhaps. But instead of raising the floor so high, what about that step of eating 8 inches up from that peaked dome top by simply bolting a round ceramic kiln shelf with stainless bolts and brackets (say, 3 or 4 of them), after stuffing some non toxic insulation up in that space at the peak behind it? Thus the inches would be taken care of for 63%, the 40 inch existing floor wouldn't turn into 36 or less by moving upward in the cone. This shape above certainly wouldn't be convex, but hey, now it is a bit pointy up there in contrast to the Pompeii plans (like 2 times pointy). The good news if that can be done is that the flat "cap" up there would be exactly in the most problematic angle, and heat from walls going up would certainly be in a hurry to cross it to get to the other side of the dome...the fire and heat arc above that would pound at the floor. So though it might not be as "heat mass retaining" - but even more heat *reflecting*, it would be the focal surface for all of the side heat - straight down pretty much. If so this could be really easy. If this might work up there, we could first try it by just holding one up there with kiln shelf supports or something before committing to the bolts. What do you think about this dome top idea?

Ok, last: Why two inches into the walls? That's the supporting depth of the bricks, about. Concerns me. Since the walls are insulated well and sitting on the raised slab, (not the ground) couldn't we just dig out the floor *within* the dome inside walls and be ok?

[peterthewolf]

Re: Wrong dimensions - Help!!

Tenorio, welcome to the growing list of !!Thank You's!!. The drawing helps understand. For any of you guys who may think I'm being a jerk to hold out past what I've so far explained, it's a learning curve going on here with your help. If our guy had followed the plans, at least in true concept even if not completely literal design, I wouldn't be getting a degree in thermal building dynamics in your university right now.

Ok, I just edited this post and condensed it - go ahead to the next one.

[lwood]

Re: Wrong dimensions - Help!!

With a 15" door height opening. That leaves a 7" door height. You need almost a 14" door ht for that dome ht to get the 63%. Will need to modify the door opening also. Maybe you will get some wicking, but this is much better.

[Tenorio74]

Re: Wrong dimensions - Help!!

Will the existing walls wick moisture up from the existing base to continue creating problems though?

I guess it should be minimal. If you want to get serious though, you could use a steel bar instead of the middle support wall (won't transfer any moisture), and use a giant steel o-ring under slab where it is in contact with the new "floating" hearth, as a moisture shield.

I think decent regular firings should control the rest of moisture trying to come in the gap laft on the outer ring.... But it will be nothing compared to what's going in now!

[roobqn]

Re: Wrong dimensions - Help!!

That is a brilliant solution and maybe the most viable outside of tearing the entire thing out. Will the existing walls wick moisture up from the existing base to continue creating problems though?

[Tenorio74]

Re: Wrong dimensions - Help!!

I like that solution, still a lot of work. Basically, tear out the the existing fire-brick floor and build back up from there leaving a 2" gap under the new floor. Your going to raise the floor by 8"? 2" air gap plus 2" concrete slab plus 4" vermiculite/concrete, then replace the fire-brick floor. Do you have 8" to play with?

Hey Lwood,

He said that his oven was about 30 inches high.... You can easily take away 8", even more. My 51 is 18" high.... Any takers?

There isn't so much material as there is manual labour.... so maybe his contractor will do it for the remainder of his fee.

Or he can do it himself and use the remaining $ for materials and red bull....

[lwood]

Re: Wrong dimensions - Help!!

I like that solution, still a lot of work. Basically, tear out the the existing fire-brick floor and build back up from there leaving a 2" gap under the new floor. Your going to raise the floor by 8"? 2" air gap plus 2" concrete slab plus 4" vermiculite/concrete, then replace the fire-brick floor. Do you have 8" to play with?

[Tenorio74]

Re: Wrong dimensions - Help!!

PS. Its hard working inside a closed oven, but not impossible.