Building Wood Stairs

For material you’ll need three 2”x12” treated boards for constructing the actual stringers. The length of them will depend upon the height of the required wooden staircase, however most likely you’ll need 10 footers. These boards should be free of all knots and cracks otherwise you’ll end up scrapping the lumber. You’ll also need a couple of 2x4s and the actual stair tread lumber. Also, you’ll need a piece of plywood and 3-1/2” framing nails and screws to assemble the wood stairs.

The first step in building wood stairs is finding the overall rise. To do this you’ll need to measure the distance between the top of the deck and the ground. It’s highly recommended to install a concrete pad for the deck stairs to rest on, however the placement is contingent upon the length of the staircase run. If you do install a concrete pad, measure the height from the top of the deck to the top of the concrete pad to get the overall rise.

Next you need to determine the overall run of the staircase. To do this, however, you first need to determine how many steps will be required. To calculate the number of steps required, divide the overall rise by 7-1/4”. This is the common step height of a step. Round up your calculation to determine the amount of steps (risers) required. Note that there is always 1 less tread than step (riser). The standard step depth (width) is 10 inches. Multiply 10 inches by the number of steps required (remember one less than the number of risers). What you calculate is the overall run of the wood stairs. You can also use this measurement to locate the center point of your concrete pad.

Now go back and calculate the exact rise for each step. To do this divide the overall rise by the number of risers calculated. Round up to the nearest 1/8th of an inch to determine the riser height for each riser.

Next it’s time to mark up the long 2×12 boards to effectively layout your stringers. This is where your framing square comes into use. The long leg of the framing square is used for the step leg and the short leg of the square is used for the riser leg. Also, when tracing out your stringers use only the outside numbers on your framing square. Apply masking tape to the framing square at the locations for the width of your riser and tread. This will make the actual tracing out of the stringer go more quickly.

With one of the 2x12s placed on a workbench, place the long leg of your square towards the end of the board and line up your masking tape marks with the edge of the board facing you. Once the square is in position, mark the outer edge with your pencil. Continue to mark the board for the required number of steps, moving the square up the board as you go. With the first stringer marked, cut it out using your circular saw and hand saw. Make sure to cut on the waste side of the line. When you near the corners, between the riser and tread lines, use your hand saw to make clean cuts. After cutting out the first stringer, use it as a template to mark and make the additional stringers required.

To strengthen the stringers attach to the bottom edge of each stringer a length of 2×4 using the 3-1/2” framing nails.

Now begins the task of actually building the wood stairs. First attach a piece of plywood to the top end of the stringers using a few framing nails with each stringer. The plywood helps to create a nailing plate for the stringers on the deck edge, versus toe nailing in the stringers and possibly splitting or damaging them. Two stringers should be located at the far edges of the plywood sheet and the third stringer centered between them. Note that the stringers should be located on 16 inch centers.

Next attach a 2×6 bottom plate to the two outside stringers. Then align up the third (center) stringer on a16 inch center spacing and attach it. The 2×6 will provide the fastening surface to the cement pad.

Attach the wood staircase stringer assembly to the deck. Make sure it is level and plumb prior to nailing it into place. When the stair stringer assembly is in proper location, nail through the plywood plate into the side of the deck. Fasten the 2×6 spacer to the concrete pad using concrete nails.

Now you can install the stair treads. Cut the stair tread depth ¾ inch longer than the stair tread width on the stringers so each stair tread has a slight overhang over the stringers. Also cut the length of the stair tread 1inch longer than the width of the two outside stingers so there is a ½ inch overlap on each side of the staircase. Fasten the stair treads to the stringers using either deck screws or nails. With any deck construction always make sure to use non-corrosive fasteners.

Once the stair treads have been installed your wood stairs are complete. Make sure, however, to add a railing to the deck stairs for safety.