How to Build Steps with Landscape Timbers | This Old House.Divide by 5? inches—the height of a 6x6 timber—to find the number of steps in the staircase. 4. Excavate the staircase area with a shovel and dig an 8- to 10-inch-wide x 3-foot-long trench along each edge of the staircase. Space the trenches at least 3 feet apart, as measured from outer edge to outer edge. 5. Use a circular.