House training is all about surfaces. The pup learns to eliminate on a given surface as opposed to inside our outside the house. When he goes to the door it's to get to the grass he's accustomed to crapping on, that's all. Used to take dogs from hay fields to the desert and they all had a heck of a time initially finding a place to poo! Watch closely and you'll see that they usually avoid sidewalks and stone if they're used to grass. Emergencies and accidents occur but if you watch, you can tell they're looking for a different spot if there's no grass around.
Standard regimen will work fine over about a month. In crate while in the house unless 100% supervised. Regular feeding/airing times. Restrict food and water after a set time in the evening.
I have an 18 mo old that was in a kennel her first 6 months and has learned to use the grass now after crate training. I don't know that she's 100% housebroken because she's still a kennel dog but she no longer messes in the kennel after I retrained her.