Good Morning! I have a customer who's husband had a bad experience with a pressure washing company years ago. This particular company blew mortar out of brick and did damage to concrete driveway (just used way too much pressure). Anyway, the mold is taking over this house so badly that one of the kids slipped down by pool and the wife slipped down in the driveway; all because everything is covered with mold! And this is a beautiful home! brick retaining walls all over, gunite pool, long circular driveway...and everything is literally green! So, the customer tells me I can clean it, but I have to be prepared to seal it immediately after cleaning. I've never sealed concrete after cleaning it. I talked to a homebuilder friend of mine, and he said that he flat out refuses to do that. He said that it makes concrete even more slippery. I was just wondering if anyone out there has ever run into anything like this. Customer was going to buy the sealant, and it costs $209.00 for every 1000 sq. ft. That seems very expensive! I'd appreciate any words of wisdom!