How to Build Deck Stairs: Complete Stringer Guide

Building deck stairs is one of the most common — and most intimidating — DIY deck projects. The math matters: wrong rise or run means stairs that feel awkward, fail inspection, or are outright dangerous. This guide walks through the complete process from measurement to installation.

Measuring total rise

Total rise is the single most critical measurement in stair building. Get it wrong and every step will be off.

Use a straight board and a level extending from the deck surface out over the landing area. Measure the vertical distance from the bottom of the board down to the ground. That's your total rise.

• Measure at the stair location, not somewhere else along the deck. Ground is rarely level.
• Account for the landing pad. If you're pouring a concrete pad at the bottom, subtract its thickness from your total rise. A typical pad is 4 inches thick.
• Measure from the deck surface, not the framing. The finished surface is where your feet land.

Calculating your stairs

The target rise per step is 7.5 inches. The IBC maximum is 7.75 inches. Anything over that fails code; anything under about 6 inches feels uncomfortably shallow.

Worked example: 36-inch deck height.

Number of steps: 36 ÷ 7.5 = 4.8 — round to 5 steps.

Actual rise per step: 36 ÷ 5 = 7.2 inches. That's within code and comfortable.

For the run, use a minimum tread depth of 10 inches. Most builders use 10.5 inches (which fits a standard 2×12 minus the nosing).

Total run: (5 − 1) × 10.5 = 42 inches. That's the horizontal distance from the deck face to the front of the bottom tread. You need 4 tread surfaces because the deck itself serves as the top step.

Marking and cutting stringers

You'll need a framing square and a set of stair gauges (small brass clamps that attach to the square). Set one gauge at the rise (7.2") on the tongue and the other at the run (10.5") on the blade.

Step-off method

Place the square on the stringer board (a straight 2×12) with both gauges touching the edge. Mark the rise and run lines. Slide the square along the board, aligning the previous run mark with the new rise position. Repeat for each step.

Cutting

• Circular saw first: Cut along each line, but stop short of where the rise and run lines intersect. Overcutting past the corner weakens the stringer significantly.
• Finish corners: Use a hand saw or jigsaw to complete the cuts at each inside corner.
• Drop the stringer: Subtract one tread thickness from the bottom riser. If your treads are 1.5 inches thick (standard 2× lumber), cut 1.5 inches off the bottom of the stringer. This ensures the first step height equals all the others after the tread is installed.

Installation

• Top attachment: Use joist hangers or a ledger board to attach the stringers to the deck frame. The top of the stringer should sit flush with the deck surface.
• Bottom landing: Set the stringers on a concrete pad, not bare ground. Attach with angle brackets or a treated bottom plate.
• Stringer spacing: 16 inches on center maximum. For stairs wider than 36 inches, use a minimum of 3 stringers.
• Use the first stringer as a template to trace the remaining ones. This ensures all stringers match exactly.

Common mistakes

• Not accounting for ground slope. If the ground slopes away from the deck, your total rise is greater than you'd expect from measuring at the deck edge. Always measure at the actual landing location.
• Overcutting notch corners. Letting the circular saw blade run past the intersection removes wood beyond the cut line, weakening the stringer's structural integrity. Always finish corners with a hand saw.
• Forgetting to drop the first riser. Without this adjustment, the bottom step will be taller than the rest by one tread thickness — a code violation and a trip hazard.
• Not checking local code amendments. IBC is the baseline, but your jurisdiction may have stricter requirements. Pull your local code before cutting anything.