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Easiest Way to Build Exterior House Stairs

Dave Jennings

Stair building doesn't have to be a daunting task. It's possible to build a set of simple exterior stairs in a few hours if you have the right tools. It also helps to have a helper or two around, but it's not really necessary, as long as you can lift a couple heavy pieces of lumber by yourself.

You can build simple exterior stairs in a few hours.

Use the right materials, and your stairs can remain strong and solid for years to come.

  1. Measure the vertical distance from the second floor to the ground, directly beneath where the top of the stair will be attached. Use your plumb bob to determine the exact spot, and make a mark there. This is measurement A. Measure from that mark to the point on the ground where the new stair will land. This is measurement B. Your marks represent two legs of a triangle.

  2. Calculate the length of the third leg, measurement C, using the Pythagorean theorem: A squared plus B squared equals C squared. This calculation is the length of your stair stringers -- the pieces of lumber which run from the ground to the second floor at an angle and to which your stair steps will be attached.

  3. Calculate the materials you will need to build the stairs. Plan a step every 7 1/2 inches or so. Use an increment between 7 and 8 inches that will give you a whole number of steps. Otherwise, one of your steps might end up being much shorter than the others. Purchase enough material for the header where the steps will attach, as well as for the number of steps, stringers and railing you will need.

  4. Build your header out of two 2-by-12 boards nailed together side by side. Attach it to the second-floor framing where the stairs will be attached. Determine where the stringers will land on the ground, and ensure that they will be supported there. A concrete pad is ideal, but any hard surface that will not allow the stairs to sink will work fine.

  5. Cut the stringers to length and lay them out against the header board. Using a straightedge, make a mark on the bottom end of the stringer, even with the ground. Use a level to make a plumb line at the top end of the stringer against the header. Cut these triangles off. Set the stringers into position and nail them to the header. Use the steel angles to strengthen that connection, nailing the steel to the header and the stringer. Cut a length of pressure-treated 2-by-4, and nail it between the stringers at the bottom.

  6. Lay out the steps using your 7- to 8-inch calculation from earlier. Cut pressure-treated 2-by-4 cleats, and screw them to the stringers at each mark, making sure they are level. Next, cut 2-by-12 steps and screw these down on top of the 2-by-4s. Use plenty of screws to ensure that the stairs are strong, and add steel angle-braces if desired.

  7. Cut 2-by-4 posts for the railings and screw them to the stringers at the top and bottom of the stairs, making sure they are plumb. Add posts along the staircase as necessary. Screw the posts to the stringers and the top of a step to add strength. Then cut 2-by-4 railings and nail them to the posts. Add steel angle braces, screws and nails wherever needed to increase the stability and strength of your new stairs.

  8. Tip

    When purchasing lumber, check the pieces for straightness by eying them. Crooked or cracked 2-by-12s do not make good stair stringers.


    Always work safely. Keep work areas well-lighted and free of debris. Use all necessary safety equipment. Use power tools only with grounded outlets. Do not leave tools unattended where children may find them.