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WaWaZat 07-03-2009 07:56 AM

Weatherproof Stucco Dome that can be Moved Later??
I have my molded refractory dome up on a stand and am ready to insulate & finish. One thing about this project is I have assembled everything so that I can take it down and take it with me when I move in a couple years. I am planning use two layers of 1 1/2" insulating blanket and NO vermiculite. I would like to build a stucco dome over the oven in a way that I can remove it when I break everything down to move it. I'm hoping that I can do this without tearing up the insulating blanket so I can reuse that upon reassembly.

I've never worked with stucco before. When a dome is built over metal lathe, is it possible to later remove the dome without having it crack or crumble? Will it be rigid enough to move it as a whole? Or maybe I'll have to build some sort of framework over the insulated oven dome, then cover this w/lathe. Any ideas for doing this simply & inexpensively?

When the typical stucco dome is built, is the insulation layer underneath what supports it? From what I've read about applying stucco, the metal lathe is used for reinforcement within the stucco layer. So if this is the case, stucco must be falling through the lathe. So in the interest of keeping the blanket in tact & constructing a dome that will be self supported, would I have to use some sort of finer backing & then a reinforcement layer over that?

I live in Chicago. What steps will I have to take to make sure rain & snow cannot penetrate the stucco dome? I plan on the finishing color being a burnt orange. From what I understand, I can add this color when mixing the finishing coat. Is there a weatherproof stucco or is there some clear weatherproofing that can be applied over the finished color layer?

Finally, what would be the best type of stucco to use for my intended application... and where do I get it? I have to imagine picking up bags of stucco in person would be a lot less expensive that having them shipped. Again, I'm in the Chicago area.

Wiley 07-03-2009 10:44 AM

Re: Weatherproof Stucco Dome that can be Moved Later??

I would suggest checking out my thread "Steel Dome Oven". My birdcage/armature I suspect is strong enough to be able to separated and removed from my completed WFO. I used window screen sewed to the inner surface of the hardware cloth which was wired to the rebar armature. This screening served several purposes: it kept the loose vermiculite insulation in place; it allowed the insulation to be inspected so I could make sure it was filling all the voids between the insulating blanket and the outer shell; and finally it gave me something to push against when applying the stucco. By having something to resist the stucco I believe it made the stucco a solid unit, and by using hardware cloth I think I have more strength than by using chicken wire.

I'm certain my finished domes shell is heavy and it would be awkward to remove and transport. Perhaps instead of using standard stucco like I did, if one used the acrylic stucco it would be lighter. Also since you know you want to be able to transport a second layer of hardware cloth or chicken wire might be warranted. This would make the shell more akin to a ferrocement structure like a boat and so it could withstand handling better.

Hope this helps,

dmun 07-03-2009 04:00 PM

Re: Weatherproof Stucco Dome that can be Moved Later??
I don't usually recommend a foil layer, as it breaks down in contact with the caustic portland cement, but you may want a foil layer over your insulation as a parting agent. You may want to think of your outer shell as sacrificial: it may not lift off as a unit, and you want it sealed at the bottom anyway to prevent water seepage into your insulation layer.

Have you ever worked with expandable metal lath? it's not nice stuff. It doesn't form into shapes like chicken wire. I'm thinking a house style enclosure would be more transportable, you could even secure handles to the steel stud structure for the planned relocation.

WaWaZat 07-03-2009 05:15 PM

Re: Weatherproof Stucco Dome that can be Moved Later??
Wow Wiley... I've just finished reading your entire thread. I like your style!! I like the armature idea, I'm just not a welder. Anyone with ideas on how to make a skeleton for a stucco shell without having to weld? The other thing is, it seems that your vermiculite may still have provided some support to your wet cement. Not sure window screen over insulating blanket would do it. I could possibly substitute a more firm, very fine metal lathe or something. I'll look into the acrylic stucco.

How did you keep water from entering around the chimney?... before the rain cover.

dmun; I'm partial to even the sacrificial dome idea over the house style. In fact, unless I can find an easy way to build a structurally independent armature to make my idea work and the materials add up economically for something more disposable, this is the route I may take.

Is there a certain type of foil that should be used?

Are there any suggestions for building the framework for a throwaway stucco shell which will support the stucco without compressing the blanket?

dmun 07-03-2009 08:05 PM

Re: Weatherproof Stucco Dome that can be Moved Later??
I'm thinking quarter inch hardware cloth might be a nice middle ground between chicken wire and expanded metal lath. It's soft enough to form to a shape. You can slit it and wire it together with any sort of wire.

And any kind of aluminum foil will do as a parting agent: you just don't want your stucco scratch coat to ooze through and seep into your expensive blanket.

Wiley 07-03-2009 09:30 PM

Re: Weatherproof Stucco Dome that can be Moved Later??

Originally Posted by WaWaZat (Post 59004)
How did you keep water from entering around the chimney?... before the rain cover.

There's a stainless steel tube section welded to the armature which also rests upon/contacts the ceramic blanket. This acts as a barrier against loose vermiculite migration. It also acts as a vent for the insulation. The outer stucco shell is sealed to this s.s. section by means of a gap created when the stucco was laid up and later filled with high temperature silicone sealant.

If that's not clear I'll try again. Oh, and don't be too intimitated by welding. Most of this is covered with stucco and welding 3/8 rebar isn't very difficult.

Thank you for the kind words.

WaWaZat 07-04-2009 11:22 AM

Re: Weatherproof Stucco Dome that can be Moved Later??
I opened the box of insulating blanket to have another look and this stuff is pretty dense & firm. So I think I will just lay my shell over it.

So just to be clear; I should use the foil as the backing for the wet stucco and a single layer of 1/4" hardware blanket as the reinforcement... allowing the stucco to penetrate it?

Are we talking standard issue kitchen aluminum foil here (Wiley what did you use?)?? From all the reading I've been doing, I have stuck in my noggin that some sort of industrial foil should be used.

Now if my above understanding is in fact correct, will simply laying & shaping the hardware cloth over the dome shape keep the cloth off the foil layer enough to become imbedded in the center of my stucco layer? Or what should I use to keep a consistent spacing? dmun, you mention slitting & tying together... are you talking about cutting around the dome opening, for instance, and tying together 2 parallel strips or is there some techniques with working with this that I should know?

Also, is there a certain gauge 1/4" hardware blanket that should be used? In a conversation with a stucco contractor, he mentioned that the stuff that can be found at the Home Centers is "cheap" and too thin a gauge.

Wiley 07-04-2009 02:40 PM

Re: Weatherproof Stucco Dome that can be Moved Later??
2 Attachment(s)

The foil I used was wide heavy duty foil like one uses in the kitchen.

In keeping with the idea that a picture is worth a thousand words I have attached two photos that you might want to spend some time looking at.

The first is my birdcage in position on top of the placed blanket. Two things to point out:
1) the darting of the hardware cloth in order to create the dome shape. One starts with a cylinder of hardware cloth wrapped around the base of the dome. The cylinder is tha same diameter as the diameter of the dome you wish to create. Now if you zoom in on the photo (I uploaded a fairly big file so you should be able to zoom in and see some detail) and follow the vertical wires of the cloth you will notice that they all head up. This is because the cloth was cut over each of the ribs of the birdcage and "darted". Darting is the term used for cutting fabric and giving it shape, darting is why your sportcoat fits and doesn't look like a potato sack. You will notice nearer the top the extra material was not removed but rather lapped one over the other. Each of these cuts was tied and the sharp wire ends bent inward before applying stucco to keep the trowel from getting hung up when applying.
The second thing I thing you might be interested in is the shadow formed by the layers of the ceramic insulation. This is showing that if you were to simply place foil over the insulation and stucco you will have areas of very thick and very thin stucco. Differences in thickness of most things will promote cracking. And so that brings us to the second photo:

This is what the dome looked like after the looose vermiculite was placed. See how the surface looks smooth and uniform? That will (and has so far at least) lessen cracking as the stucco is of uniform thickness, expanding and contracting uniformly and not focusing stresses where the thick and thin layers join.

Now for a personal thought: I think you will have a hard time creating a uniform dome shape without some sort of armature to help you hold the shape. Maybe you have some trick for doing so that I'm not aware of, if so I hope you will share. Also I think you will find working with 1/2 inch hardware cloth much more forgiving and easier than 1/4 inch cloth. Lots of reasons the biggest being you can bend the individual wires with needle nose plyers shortening the distance between rows thus taking up excess material. This isn't like working with fabric in that there is very little "bias stretch" in hardware cloth. When making a dart there will be hard spots formed which one can soften using this technique.


WaWaZat 07-05-2009 07:35 AM

Re: Weatherproof Stucco Dome that can be Moved Later??
Thx for the pix, technique details & suggestions Wiley! No, I do not have any magic planned for shaping the dome. I really appreciate the tailor lesson. Now what was your technique for forming the blanket? I know that the less cuts & seams on the blanket the better.

Also, would you explain this more?; " can bend the individual wires with needle nose plyers shortening the distance between rows thus taking up excess material."

In working with the window screen as you did, do you think I might be able to solve the uniformity issue by using screen over the blanket? I know it probably wouldn't be as ideal as using an armature, but maybe the result might be close enough???

Wiley 07-05-2009 09:30 AM

Re: Weatherproof Stucco Dome that can be Moved Later??
2 Attachment(s)
I'm not sure there is any one right way for forming the insulating blanket. If you check out the photos on my thread you will see that I made a cylinder like I spoke of before for the hardware cloth. I made vertical cuts and carefully folded the left edge of one side of the cut in and the right side of the cut over the folded in right side. The blanket is more forgiving and is to an extent moldable. I've attached a photo I don't think I included in my thread "Steel Dome Oven" to show the insulation as a cylinder standing upright before cutting and shaping for the final layer and the one in the thread showing it folded.

Regarding the screening: I used fiberglass screening as I had concerns about plastic screening melding or doing something wierd. I sewed the screening to the inside of the armature before setting the armature on top of the dome. Check the photos you will see there are areas where the distance between the inside of the aramature and the outside of the insulating blanket is maybe a 1 1/2 inches. If that were all stucco it would be significantly heavier, less insulated and more prone to cracking.

Regarding the technique I mentioned. If one takes a piece of hardware cloth and makes a cut in it and then folds the edges of the cut one over the other one is forming a cone shape. That is what happens at the end of each dart. Now on any given square of the hardware cloth if one inserts the tip of a needle nose pliers so as to grip the middle third of the length of wire on a side and gives a slight twist the straight wire forms a zig zag shape. This shortens the distance between the intersections of the ajoining wires. by doing this over an area one changes the spacing of the wires from a nominal 1/2 inch to something smaller decreasing the excess material. Basically shrinking the material. By doing this one can take the cone shape created and make is a smooth rounded curve. I would suggest you obtain a small piece (say 18 inches by 18 inches) of hardware cloth and playing with it.

Hope this helps,

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