Our house is 35 years old and the garage is drywalled with a sand finish sprayed on at the time of installation. I painted the walls and ceiling a number of years ago and decided it was time to freshen it up. When I started to roll the paint onto the ceiling, the original spray on finish started coming off as I was rolling the paint across it. I tried a few areas with the same problem. I also noticed that, if the finish did not come off right away, I could see it bubbling up as it was losing adhesion to the drywall. Yikes, what a mess. I stopped painting and scraped a bit with a wide putty knife. The spray coating came off rather easily except where the drywall had been taped and mudded over the seams and the screw heads. I never had any problems before and the roof never leaked either.
Does anyone have any ideas as to why this happened and/or a solution to the problem. Will I have to scrape the whole ceiling? Is there a better way. Also, would kilz be a good paint to use as a primer since I am down to bare drywall except for seams and screw heads?
Thanks for any guidance.