If you are going to install windows or doors in the walls of your roombox, measure the center line of the window or door back from the front wall. I eventually want my roomboxes to join together to form a house, so I want two doors in the smaller hallway boxes and a window on side of the roombox, which is centered on the door. I have set my doors and windows so that the edge of the doorframe is two inches in from the front of the box, leaving space for a piece of furniture. Using the door, I measure the opening needed for the door , and mark the door's center.
To make the window center on the door on the opposite wall I use the door center measurement, and mark the same distance back from the front of the side, on the window side of the box. Now the window opening can be lined up with the same center as the door on the opposite side.
Check the height, remembering that the base of the box will be up against the side, so your door opening needs to be at least 1/4 inch taller than you expect, when measured from the base of the side piece. Take care to mark the openings for the windows and door at the correct height for the floor. To get the door height, you will need to know what thickness of flooring you are likely to use, and mark the door opening so that it will allow for that thickness of floor. Some doors already allow for that height by the thickness of the frame. If you will need your door adjusted higher or lower, make sure you mark the correct opening size. Windows are often set so the top of the window is level with the door, or so that the window is the equivalent of 30 inches from the floor. Mark only the size of opening you need to set the door or window in place. Do not mark the door or window openings to include the surrounding trim. Any uneven edges will be covered by the trim after the door or window is in place.
