We know that most dogs wouldn't give up their indoor digs to live in a doghouse, unless perhaps it was made of liver snaps. But if you are building a doghouse for your buddy to use as shelter, there are a number of things to take into consideration.
A doghouse needs to be big enough inside for the occupant to stand up, turn around, and lie down comfortably. Measure your dog's seated height from the top of its head to the ground. Ceiling height should be 1 to 2 inches above the dog's head. Unlike some human homes, bigger isn't necessarily better, because it won't hold in the dog's body heat.
The house should sit on a platform raised an inch or two above the ground. That will not only keep the floor from getting too cold, it will also keep the structure away from pooling water, since your doghouse probably won't have flood insurance. The roof should be pitched to shed rain and be protected with several coats of exterior porch paint.
Include some kind of nesting material—straw, hay, shredded paper, pine shavings, anything that will keep your pooch warm but won't freeze, like blankets or carpet. In the chilly months, a doggy door in the form of a burlap or canvas flap will work. Just make sure it doesn't seal too tightly for air to get in.