Wrong dimensions - Help!!

[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!!

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?

[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?

[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.

[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%)...

[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!!

Peter,

When you think about lowering the dome, you have to take into account your current dome's final height in relation to the new slab+insulation+brick floor.

(metal donut would work as well, although you have to be able to take out the forms holding your poured concrete in place, so you need a gap there...)

I have never understood really where your inside flue is located, but you don't need an inside flue at all. It will probably be too low after the raise. Let the smoke go out the door - it does that in most of our oven designs as it is....

(BTW, you don't really need draw when your smoke goes out into open air. It's just to keep let it fly a little higher, and aesthetically nicer IMO) You could do yours sort of like this... (you have a metal hood to coax the smoke where you want it to go)

[peterthewolf]

Re: Wrong dimensions - Help!!

Tenorio- I'll comment back within your text. Now we're getting somewhere!

When you think about lowering the dome, you have to take into account your current dome's final height in relation to the new slab+insulation+brick floor.

---P: Yes, I have registered that. If our existing floor remained where it is (that will change if we alter it of course), right now we'd just count the inches downward from dome peak for door at 63% when it's all done...Right? I think I've got that. The new floor determines how many inches to ultimately bring the dome peak down...which should happen AFTER the floor is done. OK.

(metal donut would work as well, although you have to be able to take out the forms holding your poured concrete in place, so you need a gap there...)
---P: If the forms are not combustible, why not leave them in? Isn't that exactly the thing that would keep support beneath the slab forever as in your drawing? For just those inches right against the joint of floor meets wall, and a center support as in your drawing, it wouldn't be air, but it would be a non-combustible, non-water absorbing medium of either fiberboard or metal - which ought to heat as part of the floor-wall mass anyway; isn't that ok? I mean, it's not much mass really.

I have never understood really where your inside flue is located, but you don't need an inside flue at all. It will probably be too low after the raise. Let the smoke go out the door - it does that in most of our oven designs as it is....

How about in the morning, I'll take one more photo or two to show you the existing flue. Very spiffy oven you have there! Meanwhile, imagine you can move through walls...just take the flue that is now sitting directly over your door, and make a mirror image- right there through that wall - but on the *inside*. That's exactly where our flue is now. It is located in the ceiling of the tunnel, eight inches around, just about 5 inches in from the door itself. Since your smoke travels out your door, then (being hot) immediately wants to rise, it goes right up that flue. Ok. If this flue (other than indoor ventilation issues) weren't there at all, yes it would suffice to just let the door do the exchange. But like I said last entry, wouldn't it also not matter (if we brought down the flue inside 3 inches to the same height at 15 inches) as the door is, wouldn't it be ok to let that smoke rise *before* it went out the door? Or is there something about air pressures at the in-out exchange of air vs. hot exhaust that needs to happen exactly *through* the door opening itself? We of course could find this out by making it the last step in the process, because again, we don't even have to mess with that flue in there at all - if we simply stop it's flow anywhere in or on top of that pipe so nothing will escape through it. It's just that if it (can) work still, hey, we have a nice flue pipe up there already. If you or someone says no, go ahead and waste it, then ok I would.

(BTW, you don't really need draw when your smoke goes out into open air. It's just to keep let it fly a little higher, and aesthetically nicer IMO) You could do yours sort of like this... (you have a metal hood to coax the smoke where you want it to go)
--Good, like I just said; at the end with fewer words, yes it's nice to have that just in case aesthetics can be there. If not, hey we'll let the smoke just come out the door like they did back before the afternoon Vesuvius burped.

So are we arriving at a sensible solution here or what? What you are laying out lwood is getting the closest to what I was hoping for - a solution that we might be able to handle, that we could direct our guy - or anyone else for that matter - to do, that I can understand as a concept with specific steps, that should both isolate the heat sink, make the right air flow, and bring in some effective and efficient burn so we don't have to deforest half the planet...and at the same time not have to tear this thing down. (Looking up close at the oven from the outside, it wouldn't be just dome that tears down; we really would have to nuc it all and start over).

If any of you who have contributed, or are simply reading through this research and discussion think we are being unrealistic, please tell us. Between all of you, you have all built, consulted, repaired or torn down others' mistakes and rebuilt ovens, or at least have contributed engineering knowledge. I value and thank you all for your generous time and attention on this. It's been quite a learning experience.

Next Saturday (a week from tomorrow) we will see if the mason will cooperate with our very direct and specific directions - with the materials that I will buy (deduct) this week out of the remaining balance on this oven, and have waiting here on site. Please write any last ideas, concerns or corrections if you have them everyone as soon as you can before then. I will report back in as we go, with the corrections.

(And Tenorio, stay tuned for the last couple of flue pictures tomorrow to tie it all up).

Thank you so much!
Peter

[brickie in oz]

Re: Wrong dimensions - Help!!

I hope you have a great final outcome from your oven experience Peter.

Youll have to invite us all for a virtual pizza once up and running..

[peterthewolf]

Re: Wrong dimensions - Help!!

Brickie-
Thanks, and for all your input and photo posting (tomorrow's too). When it is done, (guess that will mean curing again), you'll get the first (photo) slice!!
-Peter

[lwood]

Re: Wrong dimensions - Help!!

We really need to see the flue(s) in closer detail. Post pictures. I really don't understand why the need to lower the dome. Raising the floor should get you out of the water and without pictures, we cant really see what you can do to modify the entry to get your proper proportions. I think trying to keep a refractory donut in the top of the dome would be a nightmare trying to keep it there in a 700F environment and having some sort of scaffolding in to hold it up would be a nuisance.

Let's look at your door/flue opening(s) and see what we can do as far as modifying that to get your 63% with the existing dome height.

Have you determined how your going to do the new hearth floor? what will the new dome height be? It was 30" now it will be ??? with the new floor and a 2" gap underneath. Let's say it ends up to be 24". That means you need a 15.2" door....There you go....your finished....assuming we are all measuring from the same place. Send pictures and we'll talk about it.

[peterthewolf]

Re: Wrong dimensions - Help!!

lwood-

I'll go out within the next 2 hours and get the pics. But because I think context will be *much* better, I'll also take a 15 second video that can go into an email. lwood *and anyone else too*- if you'll send your email address to me at

pwolf1@wolfskills.com

then I'll send the video over to you. That way I can walk up to the door, move in and aim up so you can really see it. I'll put a light on, slide in and look up into the dome, so you can see it's height and shape at the same time. That way instead of the limit in pictures you can have immediate whole context.

Dome height: I was thinking this in reverse sequence of yours. The dome is (now) a constant up there at 30". I'm thinking, leave the dome up there until the all unknowns about the finished floor are gone (the floor is finished). Things can happen (Mr. Murphy showing up to change exact expected outcomes for final estimate finished floor height).

For the dome, *simple*. After the floor is finished, measure the projected final dome height. Cut the shelf to fit up there in the cone. Drill several holes into the brick and then same spots through the shelf. Stainless bolt it it up through several SS angle brackets (nice and thick-strong). Or just bolt into the dome brick and let bent angles of the brackets hold the shelf without drilling the shelf at all. Done. The only contingency is how big around to cut the shelf so that it's position fits up there as high as we want it. And before bolting - stuff some non toxic insulation up into the point of the dome behind it. Then as hot as the shelf gets and stays, great. If instead it mostly reflects heat, well it's doing that onto the floor and the surrounding walls are the generator for that. Once the shelf is bolted up there it is solid and strong. We could simply drill a hole down to it *then*, and pour either insulating castable kiln refractory into the void, cement and rock cap it off and forget about it. If instead of it being refractory, anyone thinks it's really better to have *even more* heat mass up behind the shelf, that's about a 5 gallon bucket's worth of space and it certainly could be heated - and hold heat. But that's more wood and heating time to attain which contradicts our purpose in the first place of making the oven more efficient.

Back to floor now: Follow me please - I am not an engineer. Blowing out the front of the oven is a mess. Too extensive and the expensive metal work goes with it. It also supports the arch area above. I wouldn't mess with that front at all. If we leave that alone, it means the new floor has to be the same height as the old one was. We have a 2 inch rebar-slab down there under the dome - on top of soggy ground. That stays. If we dig out vermiculite for the supporting donut circle down to the slab, we'll need four inches of support donut to replace the missing 4" vermiculite and be on solid slab for support. So it's a 4 inch support donut, not 2".

Dig out the 4 inch vermiculite all over, exposing the whole slab. Leave 2 inches of air. Suspend the two inches of fiberboard over the edge donut, (now 4 inches vermicuite is replaced exactly) and middle "X" supports like you drew, replace the half to one inch of mortar bed onto the top of the and replace the brick. Done. **Right???**

Then: Whatever level the floor really did finish at, it should be at least reasonably close to the original, so the door is ok and it is 15 inches.

Then if we bolt the shelf so it is 24 inches above the floor on it's underside, that's 62.5%.

How's that, have I done it?????

[Tenorio74]

Re: Wrong dimensions - Help!!

Peter,

If you take out 2.5" firebrick + 4" vermiculite = 6.5"

You would need to end at the same height:

2" metal support ring and metal forms (for airspace)
+ 2" ceramic fiber board
+ 2.5" firebrick
= 6.5"

Fiber board is not very rigid and can't be like a slab in itself, especially if (as I had to do) you put it through the door in door-size pieces.

After that you can figure out your lowering of the dome - but do bear in mind what I just realized - that your dome bricks WILL STILL suck up heat, through the wall. I don't know how much though. This could be a problem for slow roasts, because the heat will wander away to the colder bricks above the new lowered dome. Butit could be negligible... Just throwing out the thought.

[peterthewolf]

Re: Wrong dimensions - Help!!

Tenorio & lwood-

It's been raining like crazy since I first took (not so good) pictures. I'm hoping to get some for you guys tomorrow during a lull in the rains. I will take stills, but in sequence going in the door, flue, then looking up at the dome. Brickie, at risk of bending you out of shape, I'll send them over, ok?

This all has given time for reflecting. First, I will be receiving the name from a good source tomorrow of a mason who can quote a demo and replace job on the floor (option 1). While we are at it, would it be of advantage to sit the new floor bricks narrow side up on their 2.5 inch sides, so the 2.5" long faces were up and down (or 5" height of floor brick) instead of flat? As in more floor to heat and hold heat than flat. Let me know, and of course that makes the floor 2.5 inches thicker therefore higher to put into the calculations. Just thought I'd ask. For those of you who suggested just demo'ing the whole oven and starting over, we believe that the ethical thing to do is give the mason the opportunity to do (our) research based orders: That is to give him the option of fixing (floor replacement, minimum), which no longer includes drilling a roof hole; only fixing the floor, possibly the dome, or doing the oven over. Know that considering the amount of money we have retained is the same amount at least, reasonably what he quoted it should take to build one in the first place, we have not ruled out demo. There is however, a LOT of material on the outside of this (very beautiful) structure, not just something like a coat of stucco. He'd likely balk and walk at the suggestion to demo, but that is his choice. As an old monk once said, "regardless of what is going on elsewhere, just keep sweeping your side of the street clean". We'll hold the option, without eagerness for the month it would take to demo, clean and start over; talk about a real mess.

So Tenorio back to your drawing just to make sure I've got it. Sorry, let me ask again: It looks like your carved slot for new floor anchoring is the anchor point to prevent the floor from sagging down and breaking. But wouldn't the metal ring snuggled against the inside surface of the wall provide exactly that support? It would have to be 2 inches high, sitting on the original slab for the airspace. This is redundant, sorry, just want to make sure. Think like a wagon wheel's metal rim sitting in there. Wouldn't *that* support rim suffice for edge support of the fiberboard, instead of having to notch into the brick wall in a circle? This is the remaining part I don't understand - it would provide vertical support, but against the (not notched) brick walls, there would be nowhere the new floor could slide or move to, to break off or fall in.

[Lburou]

Re: Wrong dimensions - Help!!

You have a private message containing my phone number....I'll try to talk you through the process to upload pictures. Download a picture resizer first, then call me tonight and we'll get past that obstacle at least.