Hi can anyone suggest a method and product to repair a crack in ceilings, Ive just recently decorated a room with a crack on the ceiling that runs along the joint of the plaster board, its the length of the room. The customer has explained there was some minor subsidance which was quickly rectified, I raked out the crack to approx 3mm in width and filled it several times with gyproc easy fill ensuring there was plenty filler pressed into the crack however after one day after decorating there is the presence of a hairline crack. Ive thought about putting a fibre glass scrim on top of the crack to add strength but that would leave the appearance of a lump on the surface of a flat ceiling or alternatively i thought about channeling the plaster along the length of the crack then insert the scrim to conceal it but this would be very labourious and time consuming. Is there a better, quicker and more effective way and if there is i would be very grateful for any advice, thank you.