How to lay out a stair stringer
A cut stringer is a sequence of identical notches marked with a framing square. Get the rise right, set the square once, and the rest is repetition. Every drawing on this page is the real layout for a 36 in deck with 48 in of run.
Want your own numbers? Open the stair stringer layout tool; it walks the square across your board notch by notch and prints a 1:1 template.
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Free: Open this 36″ layout & download the 1:1 printable template. Build Pack ($4.99 · 7-Day Pass): Multi-stringer cut list, tread rip widths, lumber shopping list & 1-page job sheet PDF.
What you need
- Framing square
- Stair gauges (a pair)
- Tape measure and pencil
- Circular saw and handsaw
- Level (4 ft)
- Clamps and sawhorses
Steps
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Measure the total rise where the stairs will land
Set the landing pad or footing first. Then measure plumb from the top of the pad to the top of the finished deck. In this example it is 36 in. Measure at the spot the bottom step lands: on sloping ground the rise can change by an inch across a few feet.
The stair we will lay out: 5 risers of 7 3/16 in climbing 36 in. -
Work out risers and treads
Divide the rise by 7 1/2 and round up: 36 in ÷ 7 1/2 = 4.80, so 5 risers of 7 3/16 in. The deck is the top step, so there are 4 treads. (If you want the top tread flush with the deck instead, there is one tread per riser and the stringer tops out one tread thickness below the deck; the tool's "Top of the stair" option handles it.) With 48 in of run available, each tread is 12 in.
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Set the framing square with stair gauges
Clamp stair gauges at 7 3/16 in on the tongue (the short arm) and 12 in on the body (the long arm). Use the outside edge of both arms. Lay a 6 ft 2x12 on sawhorses with the crown up.
Square on the first notch: the gauges ride the top edge, the outside of the arms traces the run and the rise. -
Mark the first notch
Put mark 0 on the top edge at least 4 1/4 in from the end of the board. The bottom plumb line leans back toward the end by the drop times the sine of the pitch (6 3/16 in × sin 31.0° ≈ 3 3/16 in), and the toe still needs about 1 in of wood beyond it. Set the end of the body on mark 0, push both gauges tight to the top edge and trace along the outside of the body (the run) and the tongue (the rise). That triangle is the first notch.
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Draw the bottom plumb line
Flip the square over and lay its body along the first run line with the corner exactly on mark 0, so the tongue runs down into the board. Trace along the tongue. This bottom plumb line is the face of the first riser, and it is where you measure the drop from.
Mark 0 is the top of the bottom plumb line, 4 1/4 in from the end of the board. -
Walk the square up the board
Slide the square up the board until the outside of the body starts exactly where the last rise line meets the top edge, gauges tight, and mark again. Repeat for all 4 notches. Number them as you go.
Notch 2: the square has moved one run along the board, so every notch is identical. -
Drop the bottom and mark the top cut
The first riser is cut short by one tread thickness, otherwise the bottom step ends up taller than the rest. From mark 0, measure 6 3/16 in down the bottom plumb line and mark it. From that mark, square a level cut to the lower edge of the board, parallel to the run lines: that cut sits on the pad, and it meets the lower edge at the 31.0° pitch. At the top, extend the last rise line down across the board: that plumb cut sits against the deck rim.
End cuts in red. The throat under each notch is 5 1/16 in, above the 5 in DCA 6 asks for. -
Cut, test-fit, then copy
Cut the notches with a circular saw, stopping at the lines, and finish each inside corner with a handsaw so you do not weaken the stringer with overcuts. Hold the first stringer in place, check each tread with a level, then trace it onto the other boards.
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Fasten and add treads
Hang the stringers on the rim with connectors rated for stair stringers and their listed screws. Rest the bottom on the pad, not on soil. Space stringers as your tread material requires: commonly 16 in or less for 5/4 decking and 18 in or less for 2x treads (composite decking often needs 12 in; check the maker’s stair span). Fasten treads with two screws per board at every stringer.
Common mistakes
- Forgetting the drop.
- The bottom step comes out 1 in taller than the rest. Cut the first riser short by one tread thickness.
- Measuring rise before the pad is set.
- The pad changes the rise. Set it, then measure.
- Overcutting the inside corners.
- A saw kerf past the line weakens the stringer right where it is thinnest. Stop short and finish by hand.
- Marking from the inside of the square.
- Use the outside edges of both arms, the same side for every notch.
- Using the angle of rise ÷ run for the whole flight.
- The stringer pitch is one riser over one tread; the flight line from pad to deck edge is steeper.
Check your layout before you cut
- All risers equal within 3/16 in, except the dropped first one.
- Each tread line level when the stringer is held in place.
- At least 5 in of wood left under every notch (the throat).
- The top plumb cut sits flat against the rim, with the last tread one riser below the deck surface (or level with it if you chose a flush top).
Keep going: the formulas behind each number · worked examples for common heights · rise and run table.