How to Build a Staircase: Layout, Stringers, and Framing

A staircase is one of the most heavily used parts of a house and one of the most intimidating for a first-time builder. The math looks unforgiving and the cuts look precise, but the process is mostly measurement, layout, and repetition. Stairs are a common way to open up attic, basement, or garage space, and every one of those projects means cutting an opening through the floor plane. That opening changes the building envelope, so the same care that goes into building wrap selection and installation on the exterior belongs in the framing details around the stair. A garage stair built to reach an attic workshop shows the full sequence: measure the space, calculate rise and run, lay out stringers, cut them, and assemble the treads and risers.

Stair Anatomy, Terminology, and Code Basics

Every stair is built from the same vocabulary. Treads are the horizontal surfaces you step on, risers are the vertical faces between them, and stringers are the angled boards that support both. The nosing is the front edge of the tread that overhangs the riser, and the landing is a platform that breaks up a long run. Handrails and balusters guard the open side, and headroom is the vertical clearance measured from the nosing line to the ceiling above.

How the pieces fit together

Rise and run

Rise is the vertical distance from one tread to the next, and run is the horizontal depth of the tread. Code limits both: risers typically cannot exceed 7.75 inches and treads must be at least 10 inches deep, with the variation between steps held to about 3/16 of an inch so no one trips on an unexpected step.

Stringers

Stringers carry the load. A typical stair uses three stringers for a 36-inch-wide stair, and wider stairs need more. The stringers transfer the weight of people and materials into the floor framing at the top and the landing or floor at the bottom.

Stairs are structural, not just finish work. When one is added to existing construction, the floor joists or trusses around the opening have to carry new loads, and cutting a truss without knowing its design is a fast way to create a sagging floor. The same structural strengthening methods used in building retrofits apply to stair openings, and an engineer should review the framing before any joist or truss gets cut.

Measuring the Space and Calculating Rise and Run

The calculation starts with one measurement: the total rise from the finished floor below to the finished floor above. In the garage stair example, that distance was 129.625 inches. Dividing by a target riser height between 7.5 and 7.75 inches gives the number of risers: 129.625 divided by 7.625 equals 17 risers, which works out to a consistent 7.625 inches per step. The run then gets set to 10 inches per tread, and the horizontal distance checks out against the available floor space.

1. Measure the total rise from finished floor to finished floor
2. Divide by your target riser height and round to a whole number of risers
3. Divide the total rise by that number to get the exact riser height
4. Set the tread run to meet code, typically 10 inches
5. Multiply the run by the number of treads to get the horizontal distance
6. Check that distance against the room, and add a landing if it will not fit

Space constraints drive the configuration. A straight run is the simplest and needs the most length, an L-shaped stair with a landing and a 90 degree turn fits into a corner, and a spiral stair works where floor area is tight. For challenging layouts, builders have long studied designs like a cantilevered tread spiral staircase, where each tread anchors into a wall or column with no visible support underneath.

Working out the landing

When a stair turns, the landing splits the run into two shorter flights. In the garage example, the first flight climbs from the floor to the landing and the second continues to the workshop above. Each flight gets its own set of stringers, so the landing must be framed square and level before the upper stringers go in.

Framing the Stair: Stringers, Risers, and Treads

With the numbers set, layout begins on the stringers. A framing square with a pair of stair gauge clamps marks the same rise and run repeatedly: set the gauge on the tongue for the rise and on the body for the run, then slide the square along the board marking one step at a time. The garage stair used 1.25 by 11.875 inch laminated strand lumber (LSL) for the stringers, chosen because the strand structure resists cracking at the sharp inside corner where the riser and tread cuts meet.

Cutting stringers cleanly

Cut along the marked lines with a circular saw, stopping short of the intersections, then finish the corners with a hand saw so the cut never runs past the line and weakens the board. After the first stringer is cut, use it as a template to trace the rest so every stringer matches exactly. Two sets were needed for the turning stair: one for the flight up to the landing and a second for the flight from the landing to the upper floor.

Riser and tread installation

Risers go in first. The example used half-inch MDO plywood for the risers, nailed to the stringers with finish nails, and 5/4 southern yellow pine treads with a pre-milled bullnose for the steps. The treads are screwed down to the stringers, and an extra screw driven through the back of each riser into the tread behind it locks the assembly together. The result is a stair that does not squeak under load.

Not every stair uses stringers. Cantilevered tread spiral staircases carry each step independently, which changes the structural logic entirely and puts more pressure on the wall or column connection.

Sealing and Insulating Around the Stair Opening

The stair opening is a hole in the floor plane, and in an attic or basement application it is also a hole in the building envelope. Warm, humid air from the living space rises into the attic through gaps around the stair, carrying moisture that condenses on cold surfaces in winter. Air sealing the rough opening matters as much as the stair’s framing. Foam or caulk seals the gaps between the stringers and the floor framing, and weatherstripping on any access door or hatch at the top of the stair stops the stack effect.

Those details show up in building envelope best practices and weatherstripping guidance that experienced builders rely on. A stair that leaks air performs worse than the insulation around it, because moving air carries far more heat than still air.

Air sealing checklist

• Caulk or foam every gap between stringers and floor framing
• Seal the opening around pipes, wires, and ducts that pass the stair
• Weatherstrip the attic hatch or door at the top of the stair
• Insulate above the top-floor ceiling to the full depth of the joists
• Vent the attic space so moisture has a way out

Building Science Lessons for Stair Projects

High-performance buildings treat every component, including circulation, as part of one system. The Kendeda Building at Georgia Tech, a Living Building Challenge project, demonstrates what happens when a team coordinates structure, envelope, and indoor air quality from the start, and its case study is a useful reference for any builder who wants to see the Kendeda Building’s Living Building Challenge case study. The lesson for a stair project is that decisions about openings, air sealing, and materials compound across the whole house.

Conference sessions on building science make the same point with field data. The key takeaways from the 2021 Midwest Building Science Symposium centered on air leakage testing, moisture management, and the details that separate a durable assembly from a failing one. Stair openings are exactly the kind of detail that shows up in a blower door test.

Why the details compound

One unsealed gap around a stair is a small leak. Twenty gaps across a floor plane are a measurable problem that raises heating bills and invites condensation. The builders who pass blower door tests are the ones who seal every opening, including the ones hidden behind finished walls.

Planning the Build and Working with Specialists

A stair build goes faster when the sequence is planned in advance. Confirm the floor opening and framing support before ordering material, order stringers and treads together so the stock matches, and set aside a full day for layout and cutting. Pull the permit and have the framing inspected before the treads go on, because inspection happens at the rough stage.

1. Verify the opening size and have an engineer review any joist or truss cuts
2. Order stringer material, riser stock, treads, and fasteners in one trip
3. Mark and cut all stringers before assembly starts
4. Install the landing and lower flight, then the upper flight
5. Add risers, treads, and railings in that order
6. Schedule the inspection before closing in the stair

Complex stairs justify specialist help, and finding the right person starts with a disciplined search. A structured interview process for home building hires asks candidates to walk through real jobs, name the codes they build to, and explain how they would handle a tricky landing, which quickly separates an experienced stair builder from a generalist. The same care that goes into selecting lumber goes into selecting the crew, and a stair built by the right team lasts as long as the house around it.