What's inside
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What the framing square does
A framing square lets you mark each stair tread and riser in one setup. Its long blade rests along the edge of the stringer stock; its shorter tongue lines up with the rise and run measurements. Clamped in place, the square becomes a repeatable guide for drawing the stair notches.
A standard steel framing square is usually 24 inches by 16 inches. It is inexpensive and well suited to ordinary stair work. Before laying out a stringer, check that the square is straight and that its inside corner is not damaged. A bent square or a loose stair gauge can repeat the same error across every step.
Measure the finished stair first
Measure the total vertical distance from the finished lower floor to the finished upper floor. Do not measure to the subfloor if flooring or a deck surface will change either landing height. Divide that height by the number of risers you plan to use. For example, a 98-inch rise divided into 14 risers gives a 7-inch rise per step.
Next, choose a tread run that fits the available horizontal space and suits the stair. A 10-inch run is a common starting point, but check local code for permitted rise, run, and uniformity limits before cutting. The run is the horizontal distance from one riser face to the next; the tread board’s actual depth may be greater because it can overhang the riser below.
Use a calculator rather than rounding each step separately. If the total rise does not divide evenly, use the exact result in your layout, then verify the finished stair against applicable code. Small differences between risers can become a trip hazard.
Set up the framing square
Mark the rise measurement on the tongue and the run measurement on the blade. For a 7-inch rise and 10-inch run, align one stair gauge at 7 inches and the other at 10 inches. Stair gauges are small clamps that attach to the square’s edges and hold those measurements in place.
They make repeated marking faster and reduce the chance of a gauge creeping while you trace. A pair of basic stair gauges for a framing square is usually enough. You can mark the dimensions directly on the square and use a pencil carefully, but that is slower and easier to misalign.
Set the stringer stock on a stable surface, with its straight factory edge facing up. Place the square so the tongue and blade match the rise and run, with the gauges bearing against the stock edge. Trace both legs of the square to make one step profile. Slide the square along the edge until the next position begins where the previous profile ends, then trace again.
Check the layout before cutting
Count the risers and tread notches as you go. For 14 risers, a typical stringer layout has 13 tread notches, because the upper floor serves as the final walking surface. The exact top and bottom cuts depend on how the stringer bears on the landings, so draw those cuts from the actual framing details rather than assuming every stair has the same end treatment.
Use a long level or straightedge to check that the repeated marks remain aligned. Then measure the overall run on the stock and compare it with the stair opening. A layout that is one inch too long may put the bottom step past a landing; one that is too short can leave an awkward gap at the top.
Before cutting, account for tread thickness at the bottom. If the tread sits on top of the lowest notch, the bottom riser can end up taller than the others unless you reduce the stringer’s bottom cut by the tread thickness. For a 1-inch tread, that usually means removing 1 inch from the bottom riser height. Confirm the detail against the way the stair will actually be assembled.
Cut and fit the first stringer
Use a circular saw for most of each notch, but stop short of the inside corner. Finish the corner with a handsaw or jigsaw. Cutting past the corner weakens the stringer by creating a deeper kerf than the layout calls for. That overcut is difficult to repair and can start a crack under load.
Test-fit the first stringer in place before using it as a pattern for the others. Check that it bears firmly at both landings, that the top step meets the finished floor correctly, and that the bottom riser height accounts for the tread. If the fit is wrong, correct the layout before copying it. A small error repeated across three stringers becomes a much bigger problem when the treads are installed.
For a second or third stringer, use the first as a template only after it fits. Mark around it on stock with a straight edge, then check key rise and run dimensions before cutting. Matching stringers help keep the treads level across the stair.
Choosing tools for the layout
| Tool | Best use | Trade-off |
|---|---|---|
| Steel framing square with stair gauges | Repeated step marks on standard stringers | Low cost and simple; requires careful setup and checking |
| Framing square without gauges | One-off layout or occasional stair work | Cheaper, but easier to shift while tracing |
| Story pole | Checking repeated rise positions against the total height | Useful as a cross-check; does not replace the square for marking notches |
A basic steel 24-by-16-inch framing square is the sensible choice for most DIY stair projects. A more expensive square may offer clearer markings or better corrosion resistance, but it will not compensate for incorrect measurements or a poor fit. If the stair is unusual, heavily loaded, or governed by strict local requirements, confirm the design and code details before cutting; a framing square is a layout tool, not a substitute for a sound stair plan.