Building a set of stairs for your deck can be a fun and challenging project. But don’t let stairs fool you into thinking that they are impossible to build or that you need extensive carpentry skills. In fact, stairs can easily be built with just a few hand tools, basic carpentry skills and a little math.
Stairs can be easily built just about anywhere. But first, a ledger board must be attached. This will allow the stairs to attach to the structure. Whether it is a concrete slab or wood frame, a 2×8 ledger board needs to be attached to the structure. The 2×8 can be attached with nails for now, but don’t forget to properly lag bolt, ship anchor or expansion bolt the board before you attach the stringers.
This is where the math comes in. You need to measure from the top of where the first step will be, straight down to the slab below. If there is no slab below, the ground should be properly graded and level. A measurement to this area can also be done with a level extending out to the end of the proposed staircase, back to the structure.
For sake of ease, I’ll create an example. Let’s say our deck measures 56″ from the top of our deck, to the slab below. But first there are two terms that you must understand the meaning. Rise and run. Rise is the height of each individual step, while the run is the depth or length of the step. The ideal rise and run measurements are 7 5/8″ give or take a ¼” or so. This can be translated to the number 7.625. Now we take our height (56″) and divide it by the nominal rise height (7.625) to get the number 7.3442623. Round it down to seven for a total of seven steps at 7 5/8″ rise needed for our stringer.
The run is typically 10″ but can be adjusted as needed to fit whatever material you may be using for treads. Two 2×6 boards when placed side by side equal 11″ allowing a 1″ lip to extend over each run.
Now using a framing square find the run and rise measurements on each side. Once they have been marked, you can lay the framing square on each mark flush with the edge of a 2×12. From one end to the other, trace the square seven times, butting each measurement on the square into the other down the length of the 2×12. Take a 1/ ½” off of the bottom of the stringer to adjust for the treads thickness.
Cut out the marks with a circular saw, stopping at the intersecting line and finish cutting using a handsaw of jigsaw. You now have one stringer that can be duplicated for the remaining stringers.