Sketch a room design layout. Use graph paper and a pencil. Draw a rough layout of how you want the addition to look, using shapes like squares and rectangles (you can use more detail if you are used to drawing layouts). Start with the door to the room. Include windows, other doors, closets, and room features you want to include, like a fireplace or a wood stove.
Choose the size and placement of the room addition. Check with the local zoning laws in your area to see how much you can build off of your home. According to Bank Rate's Home Improvement guide, when adding a master bedroom to a home, you can add 500 to 600 square feet to the home's foundation.
Pick a style. If you are designing a bedroom, look at bedroom styles, such as a loft, cottage or cozy-nook motif. Write a list of features you would like to add to the room, such as interior brick or large skylights.
Design the room around the amount of sunlight you want in the addition. If you are planning to add a sunroom, or sunporch, orient the room addition toward "true south," typically a few degrees different than "magnetic" south. This allows the sun to fill the room even in winter, when the sun is at its lowest angle.
Plan on windows and ventillation. Choose how many windows you want in the room and the type of ventillation. In a bedroom, living room or kitchen, for example, add a solar window, which cuts down heating, cooling, and lighting needs in a house. Situate a solar window 20 degrees off true south, which reduces solar gain (the increase in temperature caused by sunlight filtering into a space) by 4 to 5 percent.
Develop a color scheme. Choose colors that accentuate the furnishings in the room and promote a sophisticated tone. Taupe, beige, off-whites and cream and light grays are sophisticated colors. Use accent colors in bright greens, blues, red, pinks or orange to enhance the more subdued base colors. An accent wall in a brighter shade heightens the contrast and sets a clean, smart tone
Decide on a uniform flooring option. Select one type of flooring--such as bamboo hardwood flooring or linoleum--to unify the room. For kitchen enclaves or other smaller spaces, consider using alternative flooring materials for that separate space, such as tiles.
Create a design with blanace in mind. Make a list of features you want to include in the room. Note that the room should bring comfort, style and indulgence. Most guests want to stay in a room that is, more than anything else, a comfortable place to sleep with enough light and style that makes them feel welcomed and taken care of in this space.
Plan for furniture. Choose furniture pieces that borrow colors that already exist in the floor or carpeting. Add interesting focal points--like a fireplace or antique armoir--that welcome a person into the room.