Patching and Plastering - Plaster over old paint layers

Greetings and Happy New Year.

I own a 60 year old house with stucco walls inside/ out. I live in a tropical region with an average humidity of 80%. I would like to resureface the interior walls (3/4 inch stucco/ metal reinforced + multiple layers of latex paint) and my question is can I apply cement plaster over mulitple layers of latex paint or is is essential to remove it. What is the recommended preparation?

I assume that because of the relatively high humidity cement is prefered over plaster. Am I correct?

Thanks!

Hello & welcome to the forums.

The old paint should be stripped off prior to attempting to resurface the wall with stucco? or plaster. Reason I question stucco is that it's a cement product as you know & it's generally used as an exterior finish, in my experience anyway. Anyway as I said the old paint needs to go as it will impede the bond between the mew material & the existing wall.

Thanks for the response! Indeed the interior is flat concrete.

So I am in for a wall stripping job. What would be the most efficient way? Mechanical, chemical, combination?

Thanks!

Don't be too hasty to strip. If indeed it is Portland cement plaster it is probabaly hard enough to use a combination of chemical and mechanical stripping

BUT

There are bonding agents available. These are intended to bond new plaster or concrete to existing surfaces including painted surfaces. The problem with these is that the bond is only as good as the bond of the existing paint. If the paint is loose or loosens the new plaster or stucco will come loose. It might not fall off immediately but if it is not bonded it will come off sooner or later.
The easiest way to remove the paint is sand blasting. Not likely a viable option on the interior. You might also try scarifying the surface in some way to get some raw stucco revealed and get some mechanical bond. This is also not too good because to get enough paint off will make a lot of dust and be a slow tedious job.

Once, a log time ago I was able to scrape every bit of several layers of paint off of smooth troweled interior Portland cement plaster. It took a long time but the smooth concrete was so hard that when I got the paint off the wall was as good as a new wall. Maybe you could be so lucky. Also the wall may not be smooth. If it was originally a sand finish covered with lots of paint it could look smooth now but not underneath.

Why do you want to get the paint off? There are some coatings that will bond to the paint. But remember the caveat above about bonding to paint.

This is a long way to say you have work ahead of you not matter how you do it.