Wrong dimensions - Help!!

[dmun]

Re: Wrong dimensions - Help!!

Can I stuff fiberglass blanket into that space before putting the metal floor down?

Domestic fiberglass has organic binders that burn and stink with much more than attic heat. I'd go with refractory board or vermiculite concrete.

[Laurentius]

Re: Wrong dimensions - Help!!

I for one prefer Ceramic Fiber board for my floor and Ceramic fiber Blanket for my dome, and if you enclose your dome add the vermiculite mixture.
As I write we are have another earthquake after shock.

[peterthewolf]

Re: Wrong dimensions - Help!!

Laurentius-
Uh, none but an air space so far. Ok, now I get it. I was taking this literally, and of course, will be following fornobravo plans (except that this is not an "elevated tabletop level" oven) as has also just been suggested again to read fine detail of plans for sure (thanks UK). I don't know why I didn't see this before but I thought I was being advised to leave an air space. Now it is coming to me that yes I should, however, I should then *fill* that air space with insulating material - not just a chamber of open air.

Ok then. For this reason of adding insulation - it is the bituthane layer that will serve to keep water from coming up into the insulation - and the insulation will keep heat from damaging or out-gassing the bituthane. Since the slab is 2 inches above weepy ground (directly on it), and will then be covered with the bituthane moisture barrier, the new insulation will stay dry. Right?

Now. That leaves one more thing. Once we are finished blasting, we'll be finding out whether the dome walls and the insulation inside them were sitting *outside* and *below* that slab directly on weepy ground. In that case, we will need to build slab upward from the ground in a large donut around the existing slab to elevate above weepy ground. Then we can do the same bituthane application on it before rebuilding the dome.

Right??

As for insulation, we already know about vermiculite. But do you folks want to make a better suggestion? Can I stuff fiberglass blanket into that space before putting the metal floor down? And finally, I had 4 inches of space to excavate old wet vermiculite and replace. Minus 3/8 inch steel under floor support to bring brick floor back to where it was. So almost 4 inches of space to re-insulate. What's better (and equal/easier) than vermiculite?

[peterthewolf]

Re: Wrong dimensions - Help!!

Laurentius-
Uh, none but an air space so far. Ok, now I get it. I was taking this literally, and of course, will be following fornobravo plans, as has also just been suggested again to read fine detail of plans for sure (thanks UK). I don't know why I didn't see this before but I thought I was being advised to leave an air space. Now it is coming to me that yes I should, however, I should then *fill* that air space with insulating material - not just a chamber of open air.

Ok then. For this reason of adding insulation - it is the bituthane layer that will serve to keep water from coming up into the insulation - and the insulation will keep heat from damaging or out-gassing the bituthane. Since the slab is 2 inches above weepy ground (directly on it), and will then be covered with the bituthane moisture barrier, the new insulation will stay dry. Right?

Now. That leaves one more thing. Once we are finished blasting, we'll be finding out whether the dome walls and the insulation inside them were sitting *outside* and *below* that slab directly on weepy ground. In that case, we will need to build slab upward from the ground in a large donut around the existing slab to elevate above weepy ground. Then we can do the same bituthane application on it before rebuilding the dome.

Right??

As for insulation, we already know about vermiculite. But do you folks want to make a better suggestion? Can I stuff fiberglass blanket into that space before putting the metal floor down? And finally, I had 4 inches of space to excavate old wet vermiculite and replace. Minus 3/8 inch steel under floor support to bring brick floor back to where it was. So almost 4 inches of space to re-insulate. What's better than vermiculite?

[Laurentius]

Re: Wrong dimensions - Help!!

What type of insulation is under your fire brick to prevent your heat drain?

[peterthewolf]

Re: Wrong dimensions - Help!!

So far it has been suggested that we use penetrating sealer, and also this option of the bituthane type. Sealer may not last over time; certainly the bituthane would in normal conditions. But what about when the oven burns hot? We realize because of the brick floor layer over it and an airspace (not to mention the metal plate beneath brick) that heat coming down won't be at it's extreme, but certainly there is going to be heat. We already know this because the floor rapidly and continuously drained heat out of the oven. That means that some significant heat will hit the bituthane below across the airspace. Any chance we'd end up with a slight signature pizza flavor from vapors?

Pros and cons: That was con. Here's pro. Since we are demo-ing all the way down, the metal floor support is solid, not in pieces. So the only place for vapors to go is sideways, into the walls. Heat does push out, but gasses expand to fill the size of their container which means if there are any vapors from this material, I want to be totally sure our food doesn't taste like someone is tarring the roof next door. This kind of puts me back to favoring a penetrating sealer that is dry cured once it is dry. Last question on this: Metal fabricator said as long as we are using the firebrick (of course, that's the floor) over his metal, 3/8 inch is plenty without worry of warping it. Steel is a hell of a vapor barrier, except for condensation from cold wet underneath. Ah, did I just reinforce the need for sealing that slab... Or does it really matter what happens below the steel as long as there *is* an air space beneath it, wet, dry, whatever?

[stonylake]

Re: Wrong dimensions - Help!!

that's the stuff! might want to use a primer on the block before you apply it.

[peterthewolf]

Re: Wrong dimensions - Help!!

Stonylake-
You mean like bituthane?

[stonylake]

Re: Wrong dimensions - Help!!

EPDM is the most widely used roofing product available today... and was adapted from the pond liner business in the late 1970's. Think of the temperature on a black roof in 110 degree weather. EPDM does shrink, but 3% per year is pretty extreme. As far as flammability is concerned, go to your local roofing distributor and get a 4" square sample and put a lighter to it... it goes fast, and the carbon black in it makes for a big mess. If you backfill around your base, you may be better off using a peel and stick asphaltic foundation waterproofing like those produced by Tamko Corp. or WR Grace.

[lwood]

Re: Wrong dimensions - Help!!

Pond Liner?????? EPDM rubber originally formulated as rocket motor case insulation. Has great erosion rates at 3200C especially near the nozzle opening. Don't know about in a WFO however.

[Nic The Landscaper]

Re: Wrong dimensions - Help!!

How much money do you have left? I'll take a quick vacation down I-5 and build you a real wood fired oven

Seriously though, things like this make me sick. There is nothing I hate more than shady people doing less than marginal work and absolutely hosing people for money

With the moisture situation, if raising the base above soil is not an option, look into a product called multicoat to install between the concrete and vermiculite layers. Pond Liner is not a good option for wood fired ovens, as it does not perform well in warm situations and it shrinks at a rate of 3% per year (thats not published anywhere, just something that we've learned the hard way over time and gotten a few producers to "off the record" admit to.)

Anyway sounds like your on the right track with the tear down, and if it were in the budget I would come down and help.

[OscarA]

Re: Wrong dimensions - Help!!

I have nothing of value to add only good luck and keep us informed of your progress. I would love to see how this all ends.

[peterthewolf]

Re: Wrong dimensions - Help!!

Thanks dmun. Yes, we ran out of options.

It was only an hour ago when the metal fabricator was here to discuss the job, that we noticed a seep line indicating how water does in fact seep through the base layer and upward. Just noticed it, after all of this production and questions on whether the base and walls are actually wet without taking them apart to find out. There at floor level in the cement and rock work on the exterior of the oven structure where we can see both sides and front, is a moisture line where absorbed water disburses up and evaporates, which confirms what we were guessing about there being a perpetual heat sink. Off we go to play terminator...

[dmun]

Re: Wrong dimensions - Help!!

Yes! I gave up on advising you early on, when I concluded that there were no good options on your existing dome. I think you've made the right decision.

Penetrating sealer into the slab.

A pond liner may be a better/more permanent option. While you have it apart, you may as well really seal the thing.

we will put a plate of stainless on the back reflecting wall of the fireplace

They make handsome cast iron firebacks for just this application.

Good luck with the rebuild. Keep us posted.

[peterthewolf]

Re: Wrong dimensions - Help!!

Thanks everyone for your hard working input. That "favorable" phone call was the last we ever heard from the mason. He now has a letter acknowledging his abandonment of the job and we've got it from here.

Here's what we are doing:
1. Dome demo, rebuild with 24 inch interior height for 63%.
2. Then floor demo (and the room to do it). Keeping door but making it seal with metal work sill.
3. Fireplace correction in situ.
What we are leaving: -Beautiful face and arch - Chimneys -Basic structure of fireplace.

Dome demo: Your suggestions got me researching. No calcium aluminate or lime were added to the mortar. Double what he actually included in clay could have helped only marginally for high heat. Goodbye dome and all guessing about moisture wicking in it's base.

Floor demo: Down to the slab. Penetrating sealer into the slab. 3.5 inch airspace above it, then a 40 inch disc of .5 inch steel plate. It is suggested to cut it into 4 and use same intended supports ("x" shape) under the middle seams - then hi-temp caulk them shut for moisture. On that not mortar, but sand and clay bed, then firebrick. The local woodstove folks I've known say that woodstoves are lined with firebrick specifically to reduce heat to the metal surface that (would have) warped it with direct fire. Back to original floor height.

Keep door but fix it. Use sheet metal to drop interior tunnel chimney 3.5 inches to match existing 15 inch door. Have the sheet of metal up against tunnel arch to protect cement/cement dropping out to keep that part of structure with it's non high heart cement.

We figure to leave the chimney and beautiful face, and the fireplace. But we will put a plate of stainless on the back reflecting wall of the fireplace with an air space behind it, about .5 inch. Those wall bricks are against earth, but the metal will take care of that and become a heat reflector. The fireplace floor is a bridge over air, but it will take the most concentrated heat and was built with that same non-fire cement between the bricks. So we may redo just the floor surface in solid brick, or add a protecting 1/2 brick layer on top of it. We may also do the sides with an additional layer of 1/2 bricks to protect so we don't have to tear that out.

So there we are, in progress and hopefully just in time for improving weather. As we are moving through demo into rebuild, please let me know what you think.

Finally, you guys who said 'hate to say it, give it up, do it again'...thanks for banging collective heads on the wall until we woke up. The cement conclusion was the final straw. We did not ask for a temporary oven. Now we are looking forward to a great finished product that works.

--Uh, I bet you'll hear from me soon asking for advice (much more pleasant) for you... Thanks all. Now, onward!