How to Cut Stair Stringers: The Art of Creating Perfect Staircases from Scratch

I still remember the first time I attempted to cut stair stringers. Standing there with my circular saw in hand, staring at a pristine 2x12 board, I felt like a sculptor about to chisel away at marble – except I had absolutely no idea what I was doing. That disaster of a staircase taught me more about precision carpentry than any textbook ever could.

Cutting stair stringers is one of those skills that separates weekend warriors from genuine craftspeople. It's mathematical, it's physical, and when done right, it's deeply satisfying. But here's the thing nobody tells you upfront: once you understand the underlying geometry, it becomes almost meditative.

The Mathematics Behind Every Step

Before you even think about picking up a saw, you need to wrap your head around the numbers. The building code in most areas dictates that risers (the vertical part) should be between 7 and 7¾ inches, while treads (where you step) need to be at least 10 inches deep. These aren't arbitrary numbers – they're based on decades of research into how humans naturally climb stairs.

I learned this the hard way when I built a set of stairs with 8½-inch risers for my workshop. Every single person who used them complained they felt "off." That quarter-inch difference? It matters more than you'd think. Your body develops a rhythm when climbing stairs, and inconsistent measurements throw off that rhythm like a drummer missing a beat.

To calculate your layout, divide the total rise (floor to floor height) by 7.5 inches to get your number of risers. Round to the nearest whole number, then divide the total rise by that number to get your exact riser height. For the run, multiply your tread depth by one less than the number of risers (since the top step is usually the upper floor itself).

Tools That Make or Break the Job

You could theoretically cut stringers with just a handsaw and a prayer, but why torture yourself? A quality circular saw is your primary weapon here. I prefer a 7¼-inch model – anything smaller struggles with the depth of cut you need. Some folks swear by worm-drive saws for this work, and I get it. The extra torque is nice when you're cutting through dense lumber.

Your framing square becomes your best friend during layout. Get a good one – those cheap aluminum squares from the big box store will drive you crazy with their inaccuracy. I splurged on a steel Empire square fifteen years ago, and it's still dead-on accurate. Attach stair gauges to it (those little brass clamps), and you've got a foolproof way to mark consistent rises and runs.

Don't forget a sharp handsaw for finishing the cuts. Circular saws can't complete the inside corners without overcutting, which weakens the stringer. A Japanese pull saw works beautifully for this, though any sharp crosscut saw will do the job.

Selecting and Preparing Your Lumber

Here's where I'm going to ruffle some feathers: forget what you've heard about using only clear, knot-free lumber for stringers. Yes, structural integrity matters, but I've seen plenty of stringers cut from #2 grade lumber last for decades. The key is knowing how to read the wood.

Look for straight grain that runs the length of the board. Small, tight knots aren't deal-breakers if they're not located at the critical points where you'll be cutting. Avoid boards with large knots at the edges or any signs of twist or bow. Southern yellow pine makes excellent stringers – it's strong, relatively inexpensive, and machines well. Douglas fir is another solid choice, though pricier.

Before marking anything, sight down the edge of each board. Even slight warping will compound into major problems over the length of a staircase. I once tried to "make do" with a slightly twisted board, figuring I could force it straight during installation. The resulting staircase looked like it was designed by M.C. Escher.

The Layout Process: Where Precision Meets Reality

This is where the rubber meets the road. Start by determining which edge of your board will be the top (where the treads and risers will be cut). Generally, you want any crown in the board facing up – stairs naturally want to sag over time, and starting with a slight upward bow helps counteract this.

Set your stair gauges on the framing square to your rise and run measurements. Place the square on your board with the rise measurement on the tongue (the shorter arm) and the run on the blade (the longer arm). The gauges should rest firmly against the edge of the board.

Here's a trick I picked up from an old-timer in Vermont: always start your layout from the bottom of the stringer. Mark your first rise and run, then slide the square along and mark the next. This method naturally accounts for the thickness of the treads as you go. Continue until you've marked all your steps.

The top and bottom of the stringer require special attention. At the bottom, you'll need to subtract the thickness of your tread material from the first riser – otherwise, your first step will be taller than the rest. This is called "dropping the stringer," and forgetting to do it is probably the most common rookie mistake.

Making the Cuts: The Moment of Truth

Set your circular saw to its maximum depth. You want to cut as much as possible in each pass. Start with the horizontal (tread) cuts, keeping the saw base flat against the board. Cut up to where the rise and run lines meet, but don't go past. This is crucial – overcutting weakens the stringer significantly.

Next, make the vertical (riser) cuts, again stopping at the intersection. You'll be left with triangular pieces still attached at the inside corners. This is where your handsaw comes in. Carefully complete each cut, keeping your saw perpendicular to the board face. Take your time here – rushed handsaw work looks sloppy and can split the wood.

Some carpenters use a jigsaw to complete these cuts, but I find it harder to maintain accuracy. Plus, there's something satisfying about the rhythm of hand-sawing. It gives you time to think about the next steps, literally and figuratively.

The Critical Details Everyone Overlooks

After cutting your first stringer, don't immediately use it as a template for the others. First, do a test fit. Place it in position and check that your rises are consistent and your treads are level. I keep a small level and tape measure handy for this. It's much easier to fine-tune one stringer than to discover problems after cutting three.

The bottom of your stringers needs proper bearing. Code typically requires at least 3½ inches of solid bearing (the width of a 2x4). Some builders notch the bottom of the stringer to sit on a 2x4 plate, while others use metal brackets. I prefer the notch method – it's cleaner and doesn't rely on fasteners that could work loose over time.

Speaking of code requirements, most jurisdictions require a middle stringer for stairs wider than 36 inches. Don't skip this – I've seen too many bouncy, creaky staircases that could have been rock-solid with proper support.

Advanced Techniques and Personal Preferences

Once you've mastered basic stringer cutting, you might want to explore housed stringers, where the treads and risers fit into routed grooves rather than sitting on cut notches. It's more work but creates an incredibly strong, furniture-quality staircase. I built a set for my own house using this method, and ten years later, they still don't have a single squeak.

For outdoor stairs, consider using pressure-treated lumber and leaving a small gap between treads for drainage. Water pooling on wooden stairs is a recipe for rot and dangerous, slippery conditions. I learned this after rebuilding the same set of deck stairs three times in eight years.

Here's something controversial: I often cut my stringers slightly different from what the calculations suggest. If my math calls for 7.375-inch risers, I might make them 7⅜ inches (7.375 rounds to 7⅜). That tiny bit of rounding makes layout much easier and doesn't affect the feel of the stairs. Purists will howl, but in twenty years of building, no one has ever noticed.

When Things Go Wrong (And They Will)

Even experienced carpenters occasionally mess up a stringer. If you overcut slightly, you can usually reinforce the area with construction adhesive and a gusset plate on the back side. For major mistakes, though, just start over. Trying to patch a badly cut stringer is like putting lipstick on a pig – it might look okay from a distance, but it'll never be right.

I once tried to "save" a stringer where I'd misread my measurements and cut the rises at 6½ inches instead of 7½ inches. The mental gymnastics required to fix it took longer than cutting a new stringer would have. Learn from my stubbornness – sometimes the fastest way forward is to start fresh.

The Satisfaction of Getting It Right

There's a moment when you're installing a well-cut set of stringers that everything just clicks into place. The stringers sit perfectly level, the rises are consistent, and you can already envision the finished staircase. It's one of those experiences that reminds you why working with your hands is so rewarding.

My daughter recently bought her first house, and I helped her build a set of basement stairs. Watching her carefully lay out her first stringer, double-checking every measurement, reminded me of my own journey with this craft. When we set those stringers in place and they fit perfectly, her smile was worth more than any paycheck I've ever earned.

Cutting stair stringers isn't just about following measurements and making cuts. It's about understanding how people move through space, respecting the materials you're working with, and taking pride in creating something that will serve its purpose for decades. Every time someone uses stairs you've built, they're trusting your craftsmanship with their safety. That's not a responsibility to take lightly.

The next time you walk up a flight of stairs, pay attention to the rhythm of your steps. If the stairs are built correctly, you won't notice anything – your body will naturally find its pace. That invisibility of good design? That's what we're aiming for when we pick up our saws and squares. It's not glamorous work, but it's essential, and when done right, it's a thing of beauty.

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, T.W. Stair Building and the Steel Square. Drake Publishers, 1970.

Schuttner, Scott. Basic Stairbuilding. Taunton Press, 1990.

U.S. Department of Housing and Urban Development. "Stairways." HUD User, www.huduser.gov/portal/publications/destech/stairs.html.

Wagner, John. Professional Stairbuilding and the Steel Square. Craftsman Book Company, 2018.