I am in need of some help! I live in an older home that was poorly renovated…I would like to paint my walls. To do so I started to prep them (clean/sand/scrape flaking paint/spackle small cracks). While scraping some of the flaking areas I noticed I could not identify the wall material. It appears to be very smooth (as in marble smooth) and is a light brown color. One of the tiny areas I scraped turned into a huge section of “naked” wall. What should I do at this point? Do I dare keep scraping? And is the paint peeling because of the extra smooth surface? How do I find out what type of walls they are and what is on their surface? When trying to screw into them, I learned they are very hard and tend to divot where the screw was inserted. Behind this the walls appear to be like cement.