Help me understand stucco. On all the jobs I have seen, there have been two coats, the brown coat and the finish coat (with color). Most of these were over expanded metal, and a couple were over Cempo (ICFs made with recycled polystyrene and a cement slurry).
However, I always hear that ‘true’ stucco includes a scratch coat. Does expanded metal take the place of this step?
Where does chicken wire fit in? I have seen it on houses in progress, but no project that I have ever worked on. How inferior is this to expanded metal?
Replies
It depends on what your backing material is. If it is regular cement block, you can put your wire over it and do a two coat. Some do this process right onto brick & block without wire lath but the joints will show if it is is done that way. When your plastering directly onto masonry it's called parging.
In some cases, I have done 3 coats onto brick in order to float an even, flat surface in prep for the final color coat. This usually happens with older brick or stone that needs pointing and is uneven.
If your backing is nothing more than #30 felt or poly insulation, it's best to do a 3 coat where the wire has been firred out 1/4" from the backer so the scratch mud can form keys through the back of the wire mesh. Then you can do a brown & final coat.
Any time the mud doesn't bond to the backer like it would with brick or block, you should do a 3 coat as it makes it thick and strong enough for the wall you want.
All the two coat I've seen on expanded metal has been in the Minneapolis area by union lathers/plasterers, on residential construction with 2x6 walls with with plywood sheathing.You are saying this is wrong?
<Some do this process right onto brick & block without wire lath but the joints will show if it is is done that way.>That's interesting. Down here, most plain block foundations get parged. It's called stucco, but I think of that more with wire lathe. One coat on block does show the joints every time, but two coats (grey scratch plus finish) rarely show anything...especially if the masons are any good<G> Outside of the gates the trucks were unloadin',
The weather was hot, a-nearly 90 degrees.
The man standin' next to me, his head was exploding,
Well, I was prayin' the pieces wouldn't fall on me.
Off topic, way off, but I am dying to see your pics of that glass door arrangement.
I put the track in this morning, glass hasn't shown up. I'm dying to see this thing done, too<G> Outside of the gates the trucks were unloadin',
The weather was hot, a-nearly 90 degrees.
The man standin' next to me, his head was exploding,
Well, I was prayin' the pieces wouldn't fall on me.
"Where does chicken wire fit in?"
It doesn't, even though some use it because it's cheaper than expanded wire.
How inferior is it?
Inferior inferior...
Jer, I grew up in Southern Cal in the 50's when those zillions of post war stucco homes covered up the orange groves.
Every damn one of them was stuccoed with chicken wire over felt and wire. Wire between the studs about 12" apart top to bottom, then felt, then chicken wire held on with nails with little pink cardboard squares to space it out.
Chicken wire was much heavier, guess the chickens were more energetic then, this stuff that is now called poultry netting ain't the same stuff.
Joe h
is now called poultry netting. Its called poultry netting because its the politcal correctness thing to do, they dont want to hurt the chicken feeling by letting them know that they are a fricken chicken.
I know, I've seen a lot of the chicken wire stucco. I'm not saying it doesn't work, it's just that the expanded lath was really developed for plastering and is much better in my opinion. And you're right, the stuff they have now is about half the guage that old real chicke wire was.
Around here, "chicken wire" is the trade term for stucco lath. The wire is nailed over black felt paper (it actually comes in sheets or rolls, with the wire glued to the paper), and serves to reinforce the stucco.
First coat is the scratch coat, so called because it is scratched horizontally to accept the 2nd, or brown coat, with minimum waste. Final coat is the color coat, about 3/16" thick, for a total stucco thickness of about 7/8"
I have never heard of 2-coat stucco around here, although there is a one-coat stucco-like elastomeric product that is applied about 1/4" thick, over foam, one trade name being Dryvit. I have mimimun experience with such EIFS products (Exterior Insulation and Finish Systems), but I do know they are not stucco, and the application and properties are very different from traditional 3-coat stucco. Some of these EIFS products may be applied in a two-coat process.
I'm sure someone more knowledgeable than me will come along with a more in-depth explanation.
"I needed a drink, I needed a lot of life insurance, I needed a vacation, I needed a home in the country. What I had was a coat, a hat and a gun."
Raymond Chandler's Philip Marlowe
something solid like cement block, concrete, or the ICFs will function as a scratch coat, but when doing stuco over a wood frame, the base scratch coat is needed first.
Wire lathe is necessary to re=-inforce and hold things together with a wood frame behind. It also helps give a structure for the first coat to hange from for instance with the ICF which are not easyto stick to.
Chicken wire is for chickens. It used to be used by cheapos in place of wire lathe ( diamond expanded metal)
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I've been hanging around here long enough now to know that the problem in one part of the country is the solution in another part, and that there are a lot of "right" ways to do anything.
But the advice you've gotten on this one still has me puzzled.
OK, first off, stucco lathe (or stucco netting) and chicken wire are two completely different products. They are not interchangable.
Stucco netting is a real building material that conforms to certain standards, and heavier (a lot heavier) than chicken wire, and it is self-furring. That means you nail it up and it takes a shape on the wall that puts it in the middle of the stucco, rather than up tight against the wall. This is critically important, especially at corners.
As for diamond lathe vs. stucco netting, to say one is stronger than the other, you need to first decide what your objective is. Diamond lathe is great for edge details, terminations (like windows or beams), odd shapes (like bullnoses) and anywhere else you don't want a crack to propogate from.
I've trowelled on more than my share of stucco and removed that much many times over. A properly installed two- or three-coat job over stucco netting is incredibly strong in terms of impact resistance, and however you want to characterize its resistance to shear or withdrawal failure.
Not so for diamond lathe. If you cut out a section of stucco over wire (netting) you will see a 5/8" to 7/8" thick section of portland cement and sand with the wire embedded about 3/16" to 5/16" into the first coat. With diamond lathe, you see a thin coat of stucco with a little bit smushed through the diamonds, but not enough to make what would otherwise approximate ferrocement.
The impact resistance, shear, buckling resistance, and overall resistance to deflection of diamond lathe is not that good.
As an aside, someone mentioned plaster, I think. Gypsum plaster over rib lathe is a different story altogether.
Anyway, back to stucco.
All things being equal, a three-coat job will be harder, more impact resistant, and stronger in most regards than a two-coat job. But that may not be more desirable. If there is any indication that the structure will experience movement of any type, like seasonal changes from temperature or humidity, you might be better served by the two-coat. Because of its formulation it is quite a bit more flexible (strange word to use with cement) and forgiving.
So one is not better than the other without saying "better for what".
No doubt about it, the two-coat job goes on faster. And that may not be a bad thing at all.
Remember, we're talking relative terms. Just yesterday someone commented to me on how hard the two-coat job was where he was retrofitting a window. He'd cut the stucco with an angle grinder and walloped it with a hammer as hard as he could (he's a fairly strong person) two dozen times before he got significant breakage.
That's about proper mixing proportions, proper application techniques, good quality materials, and proper curing.
A good job is a good job, and you can get that with either approach.
and then you got stucco vs dryvit, dryvit is in no way stucco.
That's for sure. The synthetics and the Portland cement types should not be confused.
"and then you got stucco vs dryvit, dryvit is in no way stucco."Completely different product.
Here in San Diego area, hexagonal stucco lath goes back way into the early 20th century, and works well with good practices being followed. Stucco guys use rib lath on soffits, for obvious reasons of no sag and smaller holes.More recently, a lot of contractors have switched to stucco lath that is square gridded, about 1-1/2" apart both ways. I'm not sure why. Anyone know?Cempo acts as its own scratch coat, and holds stucco beautifully.Billedited for spelling typo
Edited 5/20/2007 11:41 pm by BillBrennen
I don't know anything about the square grid.I have seen some materials as you've described, and yes they do work really well. Some of those ICFs that use recycled cement content seem to work just fine without lathe.
But the advice you've gotten on this one still has me puzzled. OK, first off, stucco lathe (or stucco netting) and chicken wire are two completely different products. They are not interchangable.
Part of the confusion to the non-pro's is that there is a construction slang that is understood within the industry, and a lot of it is regional. Here where I live "chicken wire" is a slang term for stucco lath. It is shaped similar to chicken coop wire, and usually comes mounted to a black paper backing (although you can buy it without the paper, also). But ask any professional plasterer in my town what chicken wire is, and I would wager that to a man they would give you the definition of stucco wire lath.
Concrete workers here often refer to a fresh batch of concrete as "mud", although concrete is not mud. They also call it cement, but cement and concrete are not synonymous. Cement is an ingredient in concrete.
Similarly, drywall hangers here call gypsum board "rock", drywall finishers call their joint compound "mud" (and setting-type compound "hot mud", although it is neither), painters call ceilings "lids", electricians call romex "rope", HVAC workers call duct tape "duck tape", and so on. None of which is confusing to those of us who work with this stuff every day, but can be puzzling to the unitiated.
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edited to add: Oh yeah, and then you have Dryvit and similar elastomeric products being referred to as "synthetic stucco", when it is not in fact stucco.
"I needed a drink, I needed a lot of life insurance, I needed a vacation, I needed a home in the country. What I had was a coat, a hat and a gun."
Raymond Chandler's Philip Marlowe
Edited 5/21/2007 1:15 am by Huck
That all makes sense.While I understand the slang (we call it chicken wire, too) we had some posters here who seemed to take those terms literally -- perhaps in jest, I can't tell sometimes. I would not want this guy going out and buying chicken wire for his house, or using diamond lathe all over the outside of his house thinking he was doing a better job.As it happens, I've seen real chicken wire used for stucco, and it does not work very well at all.[side note to OP]The hexagonal weave of wire lathe is directional, and is there for a reason. It needs to be installed horizontally, minimum overlap at ends about 6" to 8", overlap between courses 2".
3 coat stucco conform to the current code IRC & IBC. 2 coat stucco has a ER report from one of the manufactures, Omega, La Habra, etc. 3 coat stucco can be put up over 17 ga woven wire ( the hex. wire you see) or welded wire ( most with the square pattern), 2 coat stucco uses a lighter gage(20) wire. 3 coat stucco is 7/8" thick and 2 coat is 3/8".
Milburn