Outdoor steps are commonly made from wood, poured concrete or stacked brick or stones. Building outdoor steps from wood is more complex than using stone or concrete, although it is easier to get accurately sized steps with wood because precut stringers eliminate inaccuracies. When building outdoor wooden steps, you will need to consider the frequency of use and exposure to the elements, as this will assist you in choosing a type of wood and weatherproofing the steps.
Calculate the step measurements. You will need to know how far the steps will extend from the structure or door they will lead from to where they will intersect with the ground, as well as how many steps will be necessary to complete the project. To do this, use a tape measure to determine the height of the object or distance from the ground to the structure (such as a deck) or doorway where the top of the steps will be located.
Divide the measurement by 17.5, because each wooden step should rise by 17.5 cm (7 inches). The height measurement in centimetres divided by 17.5 will give you the number of steps. Because each step will have a run of 30 cm (12 inches), you then multiply the number of steps by 30 to get the measurement from the back of the steps to the steps' intersection with the ground.
Shovel out a level area where the outdoor wooden steps will set; use a level tool to ensure the ground is even. Clear just a few centimetres of the ground surface. The area should be the intended width of the steps and the distance from the structure or door from which the steps will extend.
Take the measurements with you to purchase the stringers, as you will need to get the precut stringers in a length that will fit your needs. Be sure to remind the sales representative that your steps should have a 17.5 cm (7 inch) rise and 30 cm (12 inch) run. You will need at least three stringers for your steps -- one for each end and one for the middle. The rule of thumb: Try to use one stringer for every 60 to 90 cm (2 to 3 feet) of step width.
Cut and attach an anchor board for the wooden steps. Cut a 5 by 10 cm (2 inch by 4 inch) board in a length that is 7.5 cm (3 inches) shorter than the intended width of the steps. Attach the board underneath the door or onto the end of the structure where the steps will attach.
Screw stringers into place at the ends of the anchor board using a power screwdriver and 10 cm (4 inch) wood screws. The cuts on the stringer should face upward, and the bottom of the stringer should angle between the door or structure and the ground.
Cut 3.7 cm (1 1/2 inch) thick, 30 cm (12 inch) wide pieces of wood into the length of the steps' width. These are your steps. Then drive the 10 cm (4 inch) wood screws down through the pieces and into the precut stringers.
Coat the outdoor wooden steps with sealant to protect the steps from weather damage. Allow the sealant to dry overnight before using the steps.