Covering lumps with stucco?

[rsandler]

I had originally envisioned finishing my oven with an enclosure, but now, in part for aesthetic reasons and partly for space and view-preservation reasons, I'm thinking of doing an igloo style as well. So I'm trying to figure out how to go about stucco.

My biggest puzzle is how to deal with the fact that the insulated dome is pretty lumpy. In particular I added an extra inch of blanket on the top because I had a scrap that was the right size and that seemed like the place that needed the most insulation. Can I fix this with stucco, by just adding more render to the low spots and less to the high spots?

I know one way of fixing lumps is to have a layer of vermicrete, but a) I don't feel like I need the insulation with 4-5" of blanket in most places, b) vermicrete sounds like a pain and most importantly c) I don't think I have enough room between the oven and my deck to apply vermicrete and stucco. How thin can you do vermicrete?

Related question: I tied down my blanket with rebar wire. If I were to add a bunch more rebar wire, would that be a substitute for chicken wire as a base for the render? Or rather, since I'm pretty sure that in theory the answer to that is yes, would the amount of wire required be insane and way too much work?

-Ryan

[deejayoh]

Re: Covering lumps with stucco?

I don't think you want to use chicken wire for your stucco. Get lath. Chicken wire will rust and it will eventually bleed thru your stucco. For the same reason, rebar wire is not going to work either.

As for the vermicrete - I don't think you need a coat of render, but there may be other opinions. AFAIK, you can apply your scratch coat right over your lath/insulation.

[Les]

Re: Covering lumps with stucco?

I don't think you want to use chicken wire for your stucco. Get lath. Chicken wire will rust and it will eventually bleed thru your stucco. .

You sure about that? I've seen a LOT of houses with wire nailed to the paper that get a stucco finish. I know from experience that forming the lath into a dome is like playing with a box of razor blades.

[Gulf]

Re: Covering lumps with stucco?

I'm not a fan of forming chicken wire in to a dome shape either. I do agree that forming lathe into a sphere is tough. I used 1/2" galvanized mesh, cut in isoscles trapezoid shapes. But, I wouldn't recomend that either. I think it was David S. who recomended fiber reinforcement for complex curves on stucco.

[rsandler]

Re: Covering lumps with stucco?

Leaving aside the question of how to provide a base for stucco (although I appreciate the input on that as well), my real question hear is how to get stucco to make a smooth dome shape on top of very lumpy insulation. Assuming that either my stucco was full of fibers or my wire/mesh/lathe base was in the shape of the final surface, can I just pile extra render into the low places without issue, or would that cause problems?

[Gulf]

Re: Covering lumps with stucco?

I woud use vcrete/pcrete to even out the lumps and valleys. (Not necesarily for insulation, just as a means of getting back to round) I used a rotating form to get back to a true sphere. Others have used just their eye to true it back up. From what I've seen of others builds who just used their eye, that technique works great

[Tscarborough]

Re: Covering lumps with stucco?

Assuming blanket insulation, what you DON'T want to do is compress it. If I used blanket insulation and wanted to smooth it, I would would mix an 8 or 10 to 1 perlite/portland mix and use that to get the dome smoothed to an acceptable degree for final stuccoing.

[Les]

Re: Covering lumps with stucco?

my real question hear is how to get stucco to make a smooth dome shape on top of very lumpy insulation.

I went this route - http://www.fornobravo.com/forum/8/le...d-4207-21.html #95

I then rendered it with standard mortar and covered it with an acrylic stucco that had my color.

[rsandler]

Re: Covering lumps with stucco?

Sounds like vermiculite/perlite concrete is the way to go then. How thin can I make it in the "hill"areas without worrying about cracking, assuming an 8 or 10:1 mix like Tscarborough suggests?

[Les]

Re: Covering lumps with stucco?

I don't think the vermiculite will crack since it's pretty much separated by nature. I went the rebar / wire route because I didn't trust putting anything on the blanket.

[Tscarborough]

Re: Covering lumps with stucco?

It doesn't crack, and even if it does, it doesn't matter since it is in reality a temporary structure to allow a thin even coating of stucco over the dome.

Note that I am not recommending this as the best way, simply the easiest way.

Best practice is a layer of expanded lath over the blanket which is then filled with the perlcrete and then stuccoed.

[cobblerdave]

Re: Covering lumps with stucco?

Gudday
Why all the bother about lumps and bumps. Mine I recon has got a few wrinkles as well....a coat of matt earth coloured paint a bit of wheathering you get a very natural rock like appearance.
The 10 yr old down the road calls it the" fred fintstone house"....but I recon his dad put him up to that so I still feed him pizza anyway

Regards Dave

[david s]

Re: Covering lumps with stucco?

you can just keep stringing your wire around and over the dome like a spider web. Every now and again you can give a loose wire two 90 degree bends with the nose of a pair of pliers to keep them reasonably firm. I gave up using chicken wire, or lathe as reinforcing years ago because of the problem of fitting it to a compound curve. Throw in some reinforcing fibres into your stucco mix as well.

[rsandler]

Re: Covering lumps with stucco?

Why all the bother about lumps and bumps.

Principally because my wife doesn't like the look of the lumpy stucco'd ovens she's seen. Also because I was hoping to cover the stucco with a tile mosaic. In any case, I'm less concerned about the lumps from bunched up blanket, as the ridges from overlapping layers.

@david s: I actually just picked up some reinforcing fibers this morning when I went to the brick yard for a flue tile. Do you think I could cover the "valleys" with extra stucco, particularly if I've got a spiderweb of wire over them?

[Tscarborough]

Re: Covering lumps with stucco?

The problem with having thin and thick areas on stucco (especially large differences) is that they tend to cause cracking right at the edge of the thick portion. However, this type cracking is cured almost 100% by the addition of fibers.