I am a foster mom for rescue dogs, and I have seen an awful lot of accidents in my house! Here are some tips I give to people who adopt adult dogs about housetraining. It also applies to your puppy as he should know better by now.

If you know the dog can hold it (sound like this is true for your dog) and you have ruled out any medical cause (urinary tract infection, worms, etc), then you have to get back to basics.

1) Confine the dog (crate, small room, etc) when you cannot actively watch the dog. I mean really, really watch him. If he is in the same room but you are cooking dinner, you can't watch him enough. The goal is to never give him a chance to make a mistake that you can't catch.

2) Take him outside on a schedule (as often as needed to avoid accidents - start with maybe every 1/2 hour or as often as he can go). But take him out - don't let him out if you have a yard. If you just let him out it's playtime. Take him out on a leash, wait till he is done and praise him like crazy. If he does not go, increase the time between trips outside.

3) When you catch him about to go (and you will catch him because of your precautions in step 1) calmly say, "No" (don't scold!) and take him outside immediately. Again, take him outside and wait for results. Don't let him outside. Don't overreact - to a dog (especially one alone during the day) even negative attention is attention.

You should only need to do this rigid practice for a few weeks. I f you don't see improvement, you need to consider talking to a behaviorist that can give you individual attention or re-checking for medical issues.

You might also increase the amount of time with you the dogs gets in case he is looking for attention.

Good luck!