Expert: David Coil/C. R. Construction - 9/11/2005

Question
Thanks David,

I guess I'm not done with the questions (sorry)...

If I use a sheathing underneath the stucco can it be OSB or must it be plywood?  Also I noticed in some instructions that if the stucco will be placed over plywood (or OSB) that two layers of weather resistant barrier are required, however, it goes on to say that one layer of Tyvek (type) barrier is equal to two layers of felt.  If that's the case then I would assume one layer of Tyvek is all that is necessary.  Also do you have a preference between the two products?  I see less use of felt these days in leu of house wrap which I would think would provide a better moisture barrier.

Thanks again for all your help!

Erik
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Followup To
Question -
David,

One other question - is it necessary (or even recommended) to put plywood sheathing under stucco?  I've seen this done here in California on new construction (assuming it's for earthquake protection) and was just wondering what the thoughts were on that.  I see that the original stucco on the house was installed directly over the 2x4's with felt underneath.

Also wondering if you have any good leads on installing stucco.  I found a pdf file for installing it but it's not REAL specific on applying it.

Thanks,

Erik

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Followup To
Question -
Thanks David,

My only concern with the Diamond wheel was the metal chicken wire underneath the stucco.  Won't that damage the diamond blade?

Thanks,

Erik
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Followup To
Question -
Hi David,

I'm in the process of helping my brother install two new french doors on the back wall of his home.   Currently he has two windows of greater width then the new doors will be but since the stucco surrounding the windows is in bad shape I plan to rip out a fair portion of the back wall. His house is clad in stucco and I'm wondering what the best tool for removing that stucco would be.  In my mind, since the stucco consists of the stucco/plaster and the wire mesh I would assume that a grinder with a masonry cut-off wheel would do the trick.

Thanks,

Erik
Answer -
You are 80% correct.   Use a diamond wheel instead of the masonry.  Much easier.
Answer -
Amazingly the diamond wheel wont even notice the wire.  An occasional spark may appear, but you wont notice the ease of which it cuts thru....untill you hit multi layers of wire.
Answer -
You are pretty close to reality.  The plywood is mostly for wind and seismic activity, but it does make the stucco job go easier.  Stucco does not need the plywood, in some cases it is better without.  When you have just the paper and wire, you tend to put on a thicker coat.  A good thing.
Applying stucco is an art. I have done many small jobs...and still learning.  The basic principal, first  coat is to cover the wire.  Just as it starts to "set" it needs to be scratched.  Called the scratch coat.  This adds area for the second coat to bond to.  The second coat, the "brown" coat is the leveling coat to get as near smooth as possible, but rough enough for the finish coat to bond to.  The finish coat is the part that shows.  It can be fairly smooth or extremely rough.  It can have color added or painted later.  Goal is a "concrete" layer of 7/8" or greater.  

Answer
Well let me see.....OSB is rated for structural values, plywood is a better but more expensive product.  If you are using it strictly for a stucco backing...stay cheap.  As for the stucco wire.....paperbacked stucco wire is a one step process.  If you wrap the house with kraft paper, which is 36" wide...much easier than the 7' wide roll of TYVEk....and the layering of the paper aids in the water repulsion under the stucco, then install the paperbacked stucco wire, it becomes a layered, double wrapped house with 1/2 the inconvenience and nearly 1/2 the cost.  TYVEK is NOT cheap.