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DIY - How To Build Stairs - Part 2a

Free Downloadable Staircase Calculator (requires Excel) - works in conjunction with this information.

Letters in Orange signify that the formula is on the free automatic staircase calculator.

Now that you have all the basic dimensions for your staircase you can layout the stringers.

The staircase stringers are the pieces of lumber that provide the support for the stair treads and risers.

For staircases 40" or less in width you will need to make 3 stringers. For staircases from 40" to 60" you will need to make 4 stringers.

Staircase Stringer Layout:

The first thing you will need to calculate is how long the staircase stringers will be so that you can purchase the correct length of lumber. The formula to calculate the length of the staircase stringer is (all numbers are in inches):

G Total Rise2 + Total Run2 = Length of Stringer2

106.752 + 1402 = 30,995

Length of stringer = 176.054 inches or 14' 8"

carpenters (framing) square

Figure 1a - Framing Square

stair gauges

Figure 1b - Stair Gauges

Additional, detailed information on performing the stair stringer calculation

Therefore you would need to purchase 2 x 12 lumber 16' long (I always go up on size and would purchase 18' lumber so that there is plenty of room for laying out the staircase stringers and being able to trim any damaged ends).

Lay the staircase stringer material on a couple of saw horses and determine the crown. The crown edge should be facing you when standing in front of the material. Using a framing (carpenters) square, as shown in Figure 1a and a couple of stair gauges, as shown in Figure 2b, (stair gauges make the task of competitive marking go much quicker) mark the outside edges of the square on the stringer.

Additional information on determing the crown of a board.

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Number the treads as you mark out the stringer as shown in Figure 2.

Marking layout and saw lines for stairs on stringer

Figure 2 - Marking layout and saw lines for stairs on stringer

When we calculated the staircase riser height we basically ignored the thickness of the tread. As all the treads should be the same thickness all the steps will increase equally, except for the landing. As there is no tread on the landing we must lower the height of the first riser to allow for the difference.

Cut the bottom off the first riser the same thickness as one of the stair treads as shown in Figure 3.

Removing tread thickness from bottom of stringer

Figure 3 - Removing tread thickness from bottom of stringer

Cut the rest of the stair treads and risers on the stringer using a circular saw to cut to the line and finish with a handsaw. Do not cut past the lines as this will dramatically weaken the stringer.

Place the staircase stringer in the stairwell and ensure that it is a correct fit. The staircase stringer must lie flat on the floor and rest true against the upper floor's framing. Use a level to ensure that the step risers and treads are level.

Use this staircase stringer as the template for the other stringers, ensuring that the crown side is on the edge to be cut.


Straight Staircase "L" Staircase" Winder Staircase
Part 1a Part 1b Part 2b Part 3 Part 4 Part 5 Part 6a Part 6b


Staircase Terminology Repairing Stairs Stair Tread Repair Or Replacement