Even water can cause paint to come up off of porches if the paint is cracked or there are any openings in it. It gets under it and causes it to bubble and expand. You also never know if the correct paint was even used.
Many ready made products have sh in them or other chems so I don’t think that’s the answer to painted houses. They’re usually diluted down garbage too. I wash most painted houses I come across and I treat each one differently. Granted, I mainly wash vinyl though. You don’t always need sh so just use soap and water. If you come across some organics use as little sh as possible.
As far as the porch you just have to look things over real good and make the homeowner aware of the risks. If they agree to move forward I would get something in writing. If you decide to wash it be sure to rinse the porch down with clean water, apply mix to house, and instantly rinse the porch with clean water. It still might not prevent paint from bubbling up though. You never know what you’re going to run into. Some people don’t know what they’re doing and put interior paint outside. Sometimes you’re better off turning the job down. Always take before pictures just in case you don’t catch any troubled areas at first glance. If anything goes south you want them for documentation.
As far as stucco it usually requires a stronger mix. You’ll need an x jet or 12v for that.
