AAC products may be used for both interior and exterior construction, and they can be painted or coated with a stucco or plaster compound to protect them from the weather, or they can be covered with siding materials like veneer brick or vinyl siding. The key thing is that these materials should be flat, smooth, and lie flat against the wall. As long as you follow the manufacturer's instructions and apply the product according to direction, you should have no problem using it on a compound wall. Most manufacturers recommend testing a small area first, but if you are confident that the product will be used properly, you can apply it to the entire surface. Of course, if you have any doubts, you should always contact your local representative before you start working with any product. You should also know that some states require additional permits for painting or other finishing treatments be applied to exterior surfaces of buildings. Check with your local building department to make sure you have the required permits before you begin work.