If the roof is otherwise sound, cracked or failing grouting can be repaired by recoating the roof with a wet mix of cement or lime mortar.
Os yw'r to mewn cyflwr da ym mhob ffordd arall, gellir atgyweirio gwaith growtio â chraciau ynddo neu waith growtio sy'n dirywio drwy ailgotio'r to â chymysgedd gwlyb o sment neu forter calch.