If your timber framing is shrinking you may find that some of the nails that were used to fasten your plasterboard onto the framing have popped out. To fix this: 1. Drive a plasterboard screw into the stud 20 mm below the popped nail, sinking the head just below the surface. 2. Scrape away the loose paint and filler and drive the popped nail back into place. 3. Finish by covering the screw head and the nail head with premixed cellulose filler (e.g. Spakfilla), sand smooth and then paint.