How to Make Stringers
Stringers, also known as the stair carriage, are the wooden framing pieces that support the treads of a set of steps. Most stairs use two or three stringers, but the number necessary for support depends ultimately on the spacing of the stringers, the stair width, and the thickness or strength of each tread. On-line carpentry calculators can help to calculate the parts needed to build a stair. Does this Spark an idea?
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Things You'll Need
- Drawing of the stair with rise and run calculations
- Scientific or carpentry calculator
- 2-inch by 12-inch units of wood lumber (one per each stringer)
- Measuring tape
- Pencil
- Framing square
- Saw
Instructions
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1
Determine the degree of incline for the stair using the information from your drawing and a geometry-capable calculator. The tangent inverse of the angle you are looking for here will equal one step rise divided by one step run. For example, a stair with a 7 5/8-inch-high step and a 10 3/8-inch-deep step results in a 36.24 degree of incline.
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2
Find the top edges of the stringer on the 2-inch by 12-inch plank. On the broad side of the plank, draw a line at your angle of incline, starting a top corner and rising away from the 12-inch edge. An easy way to calculate this angle is to measure the corner a distance equal to one step run down the 12-inch edge of the plank, and then measure a distance equal to one step rise perpendicular to that. Mark your end point there and draw the line back to the starting corner. This line will be the vertical plumb line and basis for the rest of the stringer layout, from which you will find the geometry to draw perpendicular tread lines and parallel riser lines along the board.
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3
Use a framing square to find the top tread line on the plank. The line's length should equal one step run, and it should be drawn perpendicular to your vertical plumb line. Locate this line at the point on the board where the measurement will hit, but not overshoot, the top edge of the plank. This line will be the top of your stringer and run parallel to the floor.
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4
Returning to your vertical plumb line, draw a parallel line at the distance of one tread thickness into the stringer, or away from the short edge. This eventual trim of the stringer will prevent the top tread from being a different size than those below it.
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5
Lay out the rest of the risers and treads along the plank. Each riser line should be measured perpendicular to the tread line above it and have a length equal to one step rise. Maintain consistent dimensions of riser and tread lines until you reach the last rise of the stair.
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6
Double check the number of treads drawn on your plank before laying out what will be the bottom of the stringer.
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7
Plumb the bottom of the stringer. Using the last riser line, draw a perpendicular line across the plank. This line is the horizontal plumb line for finding the underside of the stringer
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8
Measure the depth of one tread above the horizontal plumb line and draw a parallel line. This line will be the bottom of your stringer. The trimming is necessary to ensure that the bottom step is the same size as the others in the stair.
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9
Double check your layout and final measurements against your stair drawings and then use a saw to begin cutting along the lines you have laid out. It is helpful to cut the top and bottom plumb lines first, to check that the stringer will fit properly in place before finishing it.
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10
Repeat Steps 2 through 9 on all of the stringers in the stair, being sure to keep the measurements consistent. Once the stringers are finished, the rest of the stair assembly can begin.
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Tips & Warnings
The lumber planks used for stringers should not have large knots or cupping.
Use saws and power tools with care. Check local building codes before modifying or building a new stair because finished dimensions are often strictly regulated.
References
Resources
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