Design the stairway without the landing and form your elevation plan. Make sure the drawing is to scale.
Decide where you want to place the landing. To place a landing in the center, calculate the center of the stairway. Builders often place a landing at the bottom of the stairs or at points where the stairway needs to change directions.
Use the tread height to form the sub-floor for the landing. The tread you use depends on the location for the landing. For a midway landing, use the middle tread.
Allow enough space for a 3-foot by 3-foot landing, which most builders use as a minimum. You can make a larger landing if you need one. If you want the stringer for the next group of stairs to attach to the landing, increase the length by 12 inches.
Frame the landing with 2- by 4-foot floor joists and attach plywood or another sub-floor material. You can place boards that match the wood you use for the stairs to form the landing.
Adjust your calculations for the stairs leading to and from the landing and continue with the steps according to your plan. Most builders allow at least three steps before and after the landing to create a uniform look.