Tuck-pointing is needed when the mortar holding brick or stone has deteriorated and cracked allowing water penetration into the chimney. When you have your chimney tuck-pointed it is important that all mortar joints (space between the brick/stone) are first ground out one inch and loose mortar is removed. This will allow the new mortar to properly bond to the old brick and mortar. If the bond of the brick or stone has completely separated, tuck-pointing repairs will not last. If this is the case the chimney must be rebuilt.