When I took Axel from the foster home, I was told he was fully potty trained during the day, but night time he just had no concept of. He would wake up dry on occasion, but he wasn't consistant enough for his foster mother to consider leaving him without a diaper at night.
The first four nights that I had him he woke up SOAKED every morning. S.O.A.K.E.D. I was really glad I'd brought pull-ups along. But the fifth morning he woke up dry! And again the 6th...and 7th...and every night after that. I was hopeful about what would happen when we got home, because I could see what the problem was. Axel still has one main left over institutional behavior: he will not leave his bed until he's given permission to do so. That means if he woke up to go to the bathroom he couldn't/wouldn't. The first four nights with me I'd let him play in his bed for awhile before forcing myself to get up. After that I started getting up with him as SOON as he appeared awake so that I could get him to the bathroom right away. That's when he started staying dry.
When we got home I bought a month's worth of pull ups, figuring I'd let him get used to the routine of the household before trying to ditch the nigh time diaper. But three days before Christmas Axel showed us he was ready, and confirmed the problem of him not coming out of his room without permission. So that night I told him, "No diapers tonight." and I mimed being asleep, then needing to wake up to use the bathroom, then OPENING the bedroom door to go to the bathroom. (we sleep with bedroom doors closed here.)
The next morning he woke up with a soaked bed, which I knew he would. But there was more...there was a puddle in the carpet NEXT to the bed. Hmmm...that means he got up, pulled down his pants, and peed! I took his hand and touched his wet pajamas. "Wet" I signed, making an icky face. He looked at me like, "What did you pour in my bed????" I showed him the puddle next to the bed, and signed "pee", and also pointed to his wet pajamas. Then I took him into the bathroom, and told him "pee in the toilet." as we got the wet pajamas off of him.
The next morning he woke up dry.
And the next up at my parents, although I did put a pull up on him while sleeping, he still woke up dry.
Tonight he went to bed diaper free again.
We're still having to get him to the bathroom as soon as we hear him wake up. Although we like the fact he will stay in his room until being told he can come out, it would be really nice if we could get him to get himself to the bathroom in the morning.