Old, cracked, or damaged grout can cause structural damage to a home. It can also make your nice looking tile look ugly. Once your old grout can not be restored its best to do a regrout for the best restoration results and aesthetic benefit. A regrout is when all the old grout is removed and new grout is allied. If you see damage to your grout its best to do a regrout now. A regrout should be done at first sign of damage to prevent further water damage, it can also save you time and money over potential water damage repairs.