How to Cut Stair Stringers: Mastering the Backbone of Your Staircase

Walk into any carpenter's workshop on a Saturday morning, and you'll likely find someone hunched over a sawhorse, pencil behind ear, muttering calculations while staring at a length of lumber. Chances are, they're about to tackle one of woodworking's most intimidating tasks—cutting stair stringers. It's a rite of passage that separates weekend warriors from serious builders, and for good reason. These zigzagging boards carry the entire weight of a staircase, and one miscalculation can turn your grand entrance into a lawsuit waiting to happen.

I remember my first attempt at cutting stringers. Fresh out of trade school, cocky as they come, I figured I'd knock out a simple basement staircase before lunch. By 3 PM, I was surrounded by expensive kindling and nursing a bruised ego. That humbling experience taught me what no textbook could: respect the stringer.

Understanding the Beast Before You Cut

Stair stringers are essentially the sloped boards that support your stair treads and risers. Picture them as the diagonal backbone of your staircase—without them, you'd just have a pile of wooden steps with nowhere to go. Most staircases use either two stringers (one on each side) or three (adding a center support for wider stairs).

Now, before you even think about picking up that circular saw, you need to wrap your head around some basic stair mathematics. The relationship between rise (vertical height) and run (horizontal depth) determines whether your stairs feel comfortable or like you're scaling Everest. Building codes typically mandate a maximum rise of 7¾ inches and a minimum run of 10 inches, though I've always found that 7-inch rises with 11-inch runs create stairs that feel just right—like they were built for actual human legs, not regulatory checkboxes.

The Sacred Tools of Stringer Cutting

You could theoretically cut stringers with a handsaw and enough determination, but unless you're training for some bizarre carpentry marathon, you'll want proper tools. A circular saw is your workhorse here, though don't expect it to do all the heavy lifting. You'll need a good handsaw to finish those inside corners where the circular blade can't reach.

A framing square becomes your best friend during layout—get a quality one, not that bent piece of metal from the bargain bin. I've seen too many DIYers try to save twenty bucks on a square, only to build stairs that would make M.C. Escher dizzy. Stair gauges (those little brass clamps that attach to your square) are worth their weight in gold for maintaining consistent measurements.

One tool that often gets overlooked? A sharp pencil. Sounds trivial, but a fat, dull line can throw off your cuts by an eighth of an inch, and when you're dealing with multiple steps, those errors compound faster than credit card interest.

Layout: Where Precision Meets Reality

The layout process is where most people either succeed brilliantly or fail spectacularly. Start by calculating your total rise—measure from the finished floor at the bottom to the finished floor at the top. Don't forget to account for flooring materials that haven't been installed yet. I once cut a perfect set of stringers, only to realize I'd forgotten about the ¾-inch hardwood that was going on the upper floor. Those stringers made beautiful firewood.

Divide your total rise by 7 inches (or your preferred riser height) to get the number of risers. Round to the nearest whole number, then divide the total rise by that number to get your exact riser height. Yes, it involves math. No, there's no way around it. I've met old-timers who claim they can eyeball it, but they're the same guys missing fingers, so take that with a grain of salt.

Your total run calculation follows similar logic. Take your number of treads (always one less than your number of risers—this trips up rookies constantly) and multiply by your desired tread depth. This gives you the horizontal space your stairs will occupy. Make sure you've got room for it, or you'll be explaining to your spouse why the stairs now block the bathroom door.

The Art of Marking

With calculations done, it's time to transfer those numbers to wood. Lay your 2x12 (or whatever dimension you're using) across sawhorses and prepare for what I call "the meditation of marking." This isn't a rushed process. Put on some music, grab a coffee, and settle in.

Starting at one end of the board, position your framing square with the rise measurement on the tongue (the skinny part) and the run measurement on the blade (the wide part). Your stair gauges lock these measurements in place, turning your square into a specialized stair-marking machine.

Here's where technique matters: keep the square tight against the board's edge and mark clearly along both edges. After marking your first step, slide the square along until it aligns with your previous marks. Repeat this process for each step, working your way up the stringer. The repetitive nature can be oddly soothing—until you realize you've been using the wrong measurement for the last three steps. Ask me how I know.

Cutting: Where Theory Meets Sawdust

The actual cutting process separates those who understand stringers from those who think they do. Start with your circular saw set to maximum depth, but remember—it won't cut all the way through those inside corners. This is intentional. Overcutting weakens the stringer at its most critical points.

Cut along your marked lines, stopping just short of where the riser and tread cuts meet. The remaining wood in the corners gets removed with a handsaw. Yes, it's more work. No, there's no good shortcut. I've seen people try to finish these cuts with reciprocating saws, jigsaws, even chainsaws (seriously), but nothing beats the control of a sharp handsaw.

Pay attention to the top and bottom of your stringer. The top usually needs a level cut to attach to the upper floor structure, while the bottom requires special consideration. You'll need to cut away a portion equal to your tread thickness at the bottom—otherwise, your first step will be taller than the rest. It's these details that separate professional-looking stairs from the "good enough" variety.

The Moment of Truth

After cutting your first stringer, resist the urge to immediately cut the second one. Test fit the first one in place. Check that your rises are consistent, your treads are level, and the whole assembly sits properly against both the upper and lower floors. This is when you'll discover if your measurements were accurate or if you've just created modern art.

If everything checks out (and honestly, it rarely does on the first try), you can use your first stringer as a template for the others. Clamp them together and transfer your cuts. This ensures consistency across all stringers, which is crucial for stairs that don't wobble like a drunk sailor.

Common Pitfalls and How to Avoid Them

The biggest mistake I see? People forgetting that lumber has thickness. Your treads aren't two-dimensional; they're typically 1 to 1½ inches thick. If you don't account for this in your layout, your top or bottom step will be off. Building inspectors love catching this mistake—it's like Christmas morning for them.

Another classic error involves the stringer's bearing points. The bottom of your stringer needs solid support along its entire width. Notching it to fit around floor joists or other obstructions weakens the structure. I learned this lesson when a stringer I'd notched split under load, sending my brother-in-law tumbling. He was fine, but family dinners were awkward for months.

Wood selection matters more than most people realize. Sure, you can use standard framing lumber, but stringers take serious abuse. Spring for straight, dry lumber without major knots, especially near the cut areas. That extra twenty bucks per board is cheap insurance against catastrophic failure.

Beyond Basic Stringers

Once you've mastered straight stringers, a whole world opens up. Curved stringers, housed stringers (where treads fit into routed grooves), and open stringers (where the treads are visible from the side) each present unique challenges. But they all build on the fundamental skills of accurate layout and precise cutting.

I've cut stringers for everything from simple basement stairs to elaborate curved staircases in million-dollar homes. The principles remain the same, but the stakes get higher. There's something deeply satisfying about creating the bones of a staircase that will outlast you, carrying generations of feet between floors.

Final Thoughts from the Sawdust

Cutting stair stringers isn't just about following measurements and making cuts. It's about understanding how those cuts translate into a functional, safe structure that people will trust with their lives every single day. It requires patience, precision, and a healthy respect for both the tools and the task.

Every carpenter has their stringer stories—the ones that went perfectly, and more often, the ones that didn't. These experiences build not just stairs, but expertise. So when you're standing there with your saw, staring at those pencil lines, remember that you're joining a long tradition of builders who've faced this same challenge. Take your time, measure twice (or thrice), and cut with confidence.

The stairs you build today might still be carrying people a century from now. That's not pressure—that's legacy.

Authoritative Sources:

Burrows, Rob. Building Stairs: A Complete Guide to Design and Construction. Taunton Press, 2019.

International Code Council. 2021 International Residential Code. International Code Council, 2020.

Love, Tom. Stairbuilding and the Steel Square. Sterling Publishing, 2018.

National Association of Home Builders. "Stair Construction Guidelines." nahb.org/education-and-events/education/designations/certified-graduate-builder-cgb/stair-construction

Schuttner, Scott. Basic Stairbuilding. Fine Homebuilding, Taunton Press, 2015.

U.S. Department of Housing and Urban Development. "Stairways Design Requirements." hud.gov/program_offices/healthy_homes/healthyhomes/stairways