We have just moved into a 1930s semi. Started redecoration project with stripping wallpaper in rear bedroom facing garden. We notice the walls underneath have been skimmed. But we also noticed small black marks spread across the walls, images attached, what are these? Are they serious? Do we need to treat the wall somehow? What should we do? Any comment and help would be much appreciated. Thanks.
//www.diynot.com/network/Ncall001/albums/
//www.diynot.com/network/Ncall001/albums/