Adding insulation to exterior wall; remove stucco cladding, or add on top of it


I have an exterior stucco wall that's not in super great condition. The outermost-layer was applied very badly and is flaking off, so doing a patch job or yet another layer seems like a bad idea because the layer it would be adhering to is itself not adhering well. As part of this project, I will be adding rigid foam insulation to the exterior side of the wall. My question is this: can I reasonably screw-and-glue the rigid panels right over the existing stucco cladding, or should I really remove all the prior layers of stucco first and attach the foam directly to the wall sheathing? Advantages and disadvantages to each?

Best Answer

Fastening rigid board by screwing through the stucco into the cladding (or framing) will hold the stucco in place, so its poor condition matters little. Remove any mold or rotted stucco, and remove any organic debris. I wouldn't bother trying to glue to flaking stucco.

Additionally, the stucco left in place will continue to provide a moisture, thermal, critter, and sound barrier that is desirable.

Advantages: cheaper, cleaner work, and easier to do.

Disadvantages: the exterior will be slightly (1/2 inch?) larger.

The only advantage I can think of to removing the stucco is the idea that you'll remember it as getting rid of the mess.