Looking for some advice sorry if I’ve posted in wrong section . I’ve been asked to go look tonight at a job . Basically open plan downstairs with a wood burner in middle with a door to access from both sides . Looks like the plaster has peeled away and underneath is blue grit . I’ve always used render close to heat . I’ve got no idea what they’ve done Any solutions to stop this happening again ? If attached some photos . There is 2 different sides shown