A stringer is marked with a framing square set to the riser on one leg and the tread on the other. Stair gauges (small clamps) lock those two numbers so every step is identical as you step the square down the board. Uniformity matters: the IRC allows no more than 3/8 inch variation between the tallest and shortest riser in a flight.
Mark each step by sliding the square along the board edge, aligning the locked riser and tread points, and tracing the corner. Repeat for every step. The number of full notches equals the number of treads, which is one fewer than the riser count.
Before you mark anything, you need a board long enough to hold the whole diagonal. The structural stringer length is the hypotenuse of the rise-run triangle — the straight-line distance from the top of the flight to the bottom.
For a 108-inch total rise over a 130-inch run, that is √(108² + 130²) = about 169 inches, or roughly 14 feet. Always buy longer than the bare diagonal: add 12 to 16 inches of extra length to cover the triangular offcuts lost at the top plumb cut (where the stringer meets the header or ledger) and the bottom level cut (where it lands on the pad). Running short on a stringer board is a common and avoidable waste of an expensive 2x12.
Every stringer has two repeating cut angles. The plumb cut (vertical, where the stringer seats against the header and where each riser face sits) matches the stair pitch. The level cut (horizontal, where each tread sits and where the bottom foot lands) is the complement.
These are the angles your framing square reproduces automatically when you set it to the riser and tread — you rarely cut to a protractor reading, but knowing the pitch helps when you set a saw bevel for the top and bottom cuts.
The first riser must be shortened by the thickness of one tread, otherwise the bottom step ends up taller than the rest once treads are installed. This "dropping the stringer" step is a classic first-timer mistake that produces an uneven bottom step.
After notching, at least 3.5 inches of sound wood must remain behind each notch on a cut stringer. If the layout leaves less, the board is too small for the step geometry — move up from a 2x10 to a 2x12.
A 1:1 printable template removes most of this marking risk by letting you trace the actual notch layout directly onto the board. Size the stringer first in the straight stair calculator.
The throat is the band of solid wood left behind each notch, measured perpendicular to the board's back edge. Cut too deep and the stringer becomes a row of weak triangles that can split under load. The IRC-backed rule of thumb is at least 3.5 inches of throat, which for normal step geometry rules out a 2x10 and pushes you to a 2x12. Always check the throat your geometry leaves before buying lumber — it's the difference between a stiff stair and a springy, unsafe one.
A cut (open) stringer has the steps notched out of the top edge, with treads sitting on the cut. A housed (closed) stringer keeps the board solid and routs shallow tapered pockets into its inside face, into which the treads and risers are wedged and glued. Housed stringers are stronger and quieter (no throat to weaken them) but require a router and template; cut stringers are faster and the standard for deck and basement stairs.
Small errors compound across a flight. Trace each notch with a sharp pencil against the square, not a thick carpenter's marker, and check your locked riser/tread against a tape every few steps in case a gauge slipped. Cut just inside the line and finish the corners by hand. A test fit of the first stringer against the actual rise before cutting the rest saves a wasted board.
Get the exact riser, tread, throat, and board recommendation from the stringer calculator.
A cut stringer fails at the inside corners of the notches, where the grain is weakest. Two habits prevent it. First, never overcut: stopping the circular saw at the layout lines and finishing the corner with a handsaw keeps the throat intact — an overcut kerf that runs past the corner is a built-in crack waiting to open under load. Second, keep enough throat (at least 3.5 inches of solid wood behind the deepest notch), which a 2x12 provides for normal step geometry but a 2x10 often does not.
If a stringer does split, the safe fix is to replace it rather than glue or screw it back — a repaired stringer can't be trusted with live load. For wide stairs, adding an extra mid-span stringer reduces the load each one carries and the chance of a future split.
Dropping the Stringer: Why the Bottom Step Is Shorter · How to Build Deck Stairs (Step by Step) · Rise and Run Explained · How Many Steps for a Given Ceiling Height?