This is a spot where cracks often develop. After cleaning with a a mildewcide, check carefully for a crack. If the grout is cracked, open the crack up a little wider with a grout saw (inexpensive at a ... read more
I highly recommend getting the opinion of a local arborist. If you have trouble finding one check with your local tree nursery or Botanical Garden for a referral. We have used one before and it was ... read more