There are several methods of building a model of a house or building. When I designed modular homes in the early nineties, they had to be built quickly so that the client could get a better feel for their proposed home. The method I used was to take a one quarter inch scale plan view of the house and paste it to a piece of plywood.
Then I would use the same scale elevation drawings, (exterior views of the home) and paste them to cardboard. Once pasted, I would use felt tip pens and color the different elements of the home. Afterwards, I would cut out the individual views and paste them together using glue over the plan pasted to the plywood. This way the model stays square and accurate.
The roof would be a thicker cardboard. The edges would be taped over with masking tape to simulate the fascia of the roof. I would thence draw a shingle pattern and glue it to the body of the house.
The following step would be to paint the tan colored concrete driveway and walkways, and then paint the green grass on the plan. To do the landscaping, I would use lichen for the shrubs and model trees bought from a hobby shop to finish up the model. The entire process would take less than four or five hours depending on the complexity of the home.
Interior walls are built using the same method if the interior was to be part of the model. In this case the roof would not be glued to the exterior walls. If I wanted to get real fancy, I would take a surgical knife and cut out the window panes so you would be able to see inside the model.
Another method I have used was balsa wood. Of course this method takes a bit more work than the cardboard but the detail would be much greater. Not to mention more time consuming.
How to Build an Architectural Model