Sheathe an exterior wall from the inside?


Old 04-26-09, 01:38 PM
Thread Starter
Join Date: Feb 2008
Location: US
Posts: 166
Sheathe an exterior wall from the inside?

Is it possible / advisable to sheathe an exterior wall from the inside?

I am remodeling a couple of rooms, removing wallboard, exposing studs. I would like to add some plywood or OSB sheathing on the inside of the walls (as opposed to the outside as it is normally done on new construction). Is there any reason not to do so?

P.S. The reason I want to add sheathing is that my 1958 house here in California has no sheathing, so all shear strength is provided by the wallboard, exterior stucco and a few diagonal 1xs on corner walls. Apart from the fact that this may be inadequate in earthquake country, I also have a strong suspicion that it is at least a contributing factor to the many wallboard cracks I have inside the house and the exterior stucco (there does not seem to be anything wrong with the perimeter concrete foundation, many people have checked it). So I thought that adding some plywood or OSB sheathing to the exterior walls every time I remodel a room, may actually be a good idea.

Any advice greatly appreciated.
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Old 04-26-09, 02:24 PM
Join Date: Oct 2008
Location: New England
Posts: 9,996
Well,,,, I'm not sure if it will help with your problem, but adding a layer of sheathing on the inside is not a problem. It would function in the same manner as the sheetrock, an air barrier.

Old 05-01-09, 04:31 PM
Thread Starter
Join Date: Feb 2008
Location: US
Posts: 166
Thanks for the advice. I will also be laying wallboard over the plywood sheathing. I did not mean for the plywood to be the final finished surface.

Iím primarily adding the plywood to eliminate cracks that develop over time in the wallboard. Since the foundation is ok, I assume that the next most likely reason for the cracks is underframing and/or insufficient bracing against lateral forces and seasonal expansion/contraction of the houseís wood frame.
Old 05-03-09, 06:42 PM
Join Date: Mar 2009
Location: WA
Posts: 1,167
If the wall is bare, install a few of these, instead.

WB/WBC/TWB/RCWB Wall Bracing

In Ca, you could have a problem with plywood inside, and stucco outside. Two vapor barriers.

Maybe not yours, but in a hot, humid State, the vapor barrier wants to be outside, to stop moisture.

The plywood has a permeance of .65 or so, enough to practically stop moisture vapor. If the stucco leaked, normally any moisture would dry to the inside (warm), but with two vapor stops, it would be trapped inside, on the face of the ply, wetting your insulation. Here is some reading for you, notice the different locations:

BSD-012: Moisture Control for New Residential Buildings —

Panhandle Insulation

Why risk it, if a metal wall brace will do? Maybe I'm nit-picking...... Be safe, G

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