Building a house (even a small house) is a big project! It's best to start something that you can finish without too much stress. You can always add a room on later. If you become a cob addict you can add on each year.
Smaller buildings usually require wood of smaller dimensions to support the roof. This reduces the need to cut trees and spend money.
A well-designed small building is all a person needs. It's cozy and easier to maintain. Measure the rooms where you live now so you can quantify the sizes of spaces.
A small home encourages more time spent outside in Mother Nature. Design outdoor living spaces around your home. Patios, covered porches and doorways that invite you outside add a lot to a home.
Design your home around what you intend to do in it. Write down your daily activities and think about what time of day you're likely to do each thing. Take advantage of natural light and heat when the sun shines into different parts of the house. Make a rough sketch using circular shapes to represent your daily activities. This will give you a basic layout for your design. Try arranging the layout in a variety of ways. How can one place be used for more than one purpose? Plan the flow of people-traffic carefully.
Remember to include lots of storage space (at least 15% of the floor area). A small house feels bigger when it's tidy and not cluttered. Design in lots of closets, shelves, niches, and hooks. Plan a shed off the house for wood and tool storage.
People almost never stand right next to a wall. This means the walls don't need to be as tall as you are, if the ceiling is slanted/ sloped. Be willing to let go of what you're used to while you are imagining your home. The lower the walls, the less work you'll have to do to make them, and the less energy it will take to heat your home. Make sure you won't bump your head on the eaves while walking outside.
Think about efficient use of kitchen space. An old wive's tale says to put your sink, refrigerator and stove in a triangular relationship to each other. Old wives probably know what they're talking about. Notice kitchens. Which ones are comfortable and efficient? What makes them that way? Copy them. Arrange a visit to see the inside of a yacht or houseboat to get some good ideas for kitchens designed to take up a minimum amount of space.
It's easy to make beautiful furniture out of cob. Furniture that's built against the walls takes up a lot less room than movable furniture and leaves the floor space more open.