Rottweiler potty problem

Question
I have a 9-month old Rott/Shepherd mix.  We got him at 8 weeks old last December.  We also have a 13-year old Rott/Lab mix, very well-behaved and gentle.  We have a dog door that leads to a large two-tiered deck, with a hot tub, a stairway that goes to a good-sized lawn area.  Had a very challenging housetraining period with the pup.  Finally he goes outside, but now it's always on the deck, pee and poop. Several times on the hot tub cover (which he has torn up anyway).  They both stay out during the day while we are at work, but have lots of toys.  Have had pup in training a few months ago, and was doing all right, but can't break the poop on the deck cycle.  Don't know how to catch him at it and this a.m. when we got up, he had done it on the rug in the house!  At our wit's end.  Any suggestions would be much appreciated.  Thank you.

Answer
Your problem is that you never taught the dog where to go, it seems you just assumed he would know enough to go off the deck.  Really, the only way to teach a dog to go in a particular spot is to take him there, praise him (and occasionally reward him with food or a toy) when he does his business there, and not allow him access to other locations until he is trained.  People use dog doors out of convenience, but they are not a training tool.  Also, dogs that use dog doors may not truly be house trained, and yours may not be if he decided to use the rug as a commode. He should not be scolded (lest he learn to fear pottying in front of humans, in which case it's hard to train and praise him while he's on leash).  And, frankly, if he urinates or defecates in the house, he should be crated or confined when you can't supervise him, so that he doesn't get any opportunities to soil indoors.  Sorry to give you such bad news, but I think it's back to housetraining 101.  If you need some additional help, there's a great little booklet, "Way to Go - How to House Train a Dog of Any Age" by Patricia McConnell.  Should be available on Amazon.