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I have a house that I gutted and rebuilt with new "exterior" walls within the existing exterior walls. These walls are sheathed in the inside with 3/8 exterior plywood, and I would like to use stucco or similar to give them the feel of a south-Mediterranean white-washed wall (smooth but uneven).

I keep being told that I will not need house wrap to cover the substrate (the ply) since I am stuccoing only the interior. Somebody has mentioned there are products that I could use to apply directly to the ply without the need for lath, but most agree I should lath the walls first, any thoughts?.

What I am wondering is: since these walls are not exposed to the elements what kind/product/system you would recommend. I have spent countless hours on the net and everybody talks about exterior walls, but haven't found any references to interior walls..

Good question.

YES, you want to put on house wrap or building paper over the plywood, but for a different reason than for working outside.

Even though the wall isn't exposed to rain and the elements, plywood can absorb water from the wet mortar and warp and expand. This warping can crack the stucco.

I had this happen to me a few years back. I put plywood and interior plaster over metal lath and bare OSB. The OSB was put on for bracing in an 1870's house we were working on. A couple days later, the area over the OSB spider web cracked badly.

Fortunately. on inside plaster that got painted, I just filled in the cracks. With stucco or a rough texture, you would need to coat the whole wall over again if this cracking happened.

As far as a material that can be applied directly over plywood without metal lath, I would never trust anything like that.

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