Think about a number of rooms and their deployment, rooms' layout and lightening both natural and artificial, size and placement of windows.
You need to consider all details - location according to the four directions of the world, placement of the front door. The precise and detailed floor plan makes clear a task assigned before builders, allows avoiding ambiguity and mistakes during construction. Planning is the most important part of the construction process. All your ideas of an ideal cozy house will be implemented when you begin construction from the planning stage. It is a time-consuming process but it is extremely effective to design a home fully responding to your desires and taste. Building a house from the ground is an incredibly rewarding experience.
