My husband tiled and grounted the stairs. He installed a subfloor and did all the proper steps to install tile. He did not use a liped tile on the horizontal step, but put the horizontal and riser tile at a 90 degree angle with grout in between. Now that portion of the grout is cracked all across the step, no place else. Did he do something wrong (preping the floor) or do we have to go with a liped tile and start all over agian?