How to Build Stairs: Step-by-Step Guide
A comprehensive guide to building residential stairs from measurement to finish. Whether you're building interior stairs or deck steps, these fundamentals apply.
1. Measure the Total Rise
Measure from the finished floor at the bottom to the finished floor at the top. This is your total rise. Be precise — even 1/4" error compounds across all steps. If the upper floor isn't finished yet, add the expected flooring thickness.
2. Calculate Rise and Run
Divide total rise by your target rise per step (aim for 7" to 7.5"). Round to the nearest whole number — that's your step count. Divide total rise by step count for exact rise per step. Standard run per step is 10" to 11". Use our Rise & Run Calculator for instant results.
3. Determine Stringer Length
Stringer length = √(total rise² + total run²). Total run = (number of steps - 1) × run per step. You need one fewer tread than risers because the top floor acts as the final tread. Buy 2×12 boards long enough for this measurement plus 12-18" extra.
4. Lay Out the Stringer
Use a framing square with stair gauges set to your rise and run measurements. Starting from one end of the 2×12, mark each step by aligning the rise on the tongue and run on the blade. Mark all steps, then add the top and bottom cuts.
5. Adjust for Tread Thickness
At the bottom of the stringer, remove the thickness of one tread from the first riser. This is critical — without this adjustment, the first step will be too tall (by one tread thickness) and the last step too short. This is the most common mistake in stair building.
6. Cut the Stringers
Cut along the marked lines using a circular saw. Stop 1/2" before the inside corner and finish with a handsaw or jigsaw to avoid over-cutting. Check that the throat (narrowest point) is at least 3.5" for structural integrity.
7. Test Fit and Install Stringers
Test fit the first stringer before cutting the rest. Check that the rise is consistent top to bottom. Install stringers using stringer hangers at the top (attached to header or rim joist) and anchor them at the bottom to the landing or floor.
8. Install Risers (Optional)
If using closed risers, install riser boards before treads. Use 3/4" plywood or 1× lumber. Attach with construction adhesive and screws from behind the riser into the stringer notch.
9. Install Treads
Attach treads to stringers using construction adhesive and 2.5-3" screws (2 per stringer). Treads should overhang risers by 3/4" to 1-1/4" (nosing). Check that each tread is level side-to-side and the nosing overhangs are consistent.
10. Install Handrails and Balusters
Install newel posts at top and bottom. Attach handrail at 34-38" above the nosing line. Install balusters to maintain the 4" sphere rule. Extend the handrail 12" past the top riser horizontally.
Pro Tip: Always build a mock-up of one or two steps before cutting all your stringers. Test the rise and run by walking on the mock-up — it should feel natural and comfortable.