Mud cracking is the deep, irregular cracks resembling dried mud in dry paint film.
Paint is applied too thickly, usually over a porous surface
Paint is applied too thickly, to improve inherent poor hiding (coverage) of lower quality paint
Paint build up in corners during application
Remove coating by scraping and sanding. Prime and repaint, with a premium water-based paint, and a roller with appropriate nap length. Sanding the surface smooth before repainting with a premium water-based paint can also repair mud-cracked areas.
Premium quality paints have a higher solids content, which reduces the tendency to mud crack. They also have very good application and hiding properties, which minimises the tendency to apply the paint too thickly. Dulux recommends Dulux Wash&Wear®.