Last Updated on September 3, 2026 by Sam Wood Worker
Deck stairs look simple, but small errors can make them uncomfortable or unsafe. One riser that is taller than the others can create a trip hazard. Weak stringer connections can allow movement. A poor landing can change the height of the bottom step after winter.
The safest approach is to plan the complete staircase before cutting any lumber. This means confirming the finished deck height, landing height, stair dimensions, tread material, stringer spacing, handrails, guards and support details.
This guide explains the basic process. Use approved plans and check your local building requirements before construction. Stair rules differ by location, and decking or railing manufacturers may require their own framing and fastening methods.
Quick answer: How do you lay out deck stairs?
Measure the total rise from the finished deck surface to the finished landing. Divide that height by a suitable riser height that meets local code. Round the result to a whole number of risers. Then divide the total rise by that number to find the exact height of every riser.
Next, confirm the required tread depth or horizontal run. Mark the rise and run repeatedly on suitable stringer lumber with a framing square or accurate template. Cut only to the inside corners, test the first stringer in place, and use it as the pattern for the remaining stringers.
Do not use one online stair dimension without checking local rules. The 2021 IRC commonly used for residential guidance allows a maximum riser height of 7¾ inches and a minimum tread depth of 10 inches, but adopted codes and deck guides can differ.
Important stair terms
| Term | Simple meaning |
|---|---|
| Total rise | Vertical distance from the finished landing to the finished deck surface |
| Riser | Vertical height from one tread to the next |
| Tread | Horizontal surface where you step |
| Run | Horizontal layout distance for each step |
| Nosing | Front edge of a tread that projects beyond the riser below |
| Stringer | Sloped structural member supporting the treads |
| Landing | Level surface at the top or bottom of the stairs |
| Handrail | Graspable rail used while walking on the stairs |
| Guard | Barrier that helps prevent a fall from an open side |
Step 1: Check permits and available space
Start with the approved deck plan. Confirm where the stairs may leave the deck and where the bottom landing will sit.
A staircase uses more yard space than many homeowners expect. Total horizontal travel is based on the number of treads and their run. The landing adds more space. Do not point the stairs toward a fence, steep slope, gate, window well or narrow path.
Check property setbacks and easements. A stairway can extend beyond the main deck footprint and create a zoning problem even when the deck itself fits.
Also check overhead clearance, lighting, drainage and underground utilities. Contact 811 before digging stair or landing footings.
Step 2: Measure the total rise correctly
Measure from the top of the finished deck surface to the top of the finished landing. Include the actual thickness of deck boards, stair treads, concrete, pavers or other finished materials.
Do not measure only to bare soil. The landing surface may raise the bottom elevation. Changing it later changes the first riser.
Place a straight board or long level out from the deck edge and measure vertically to the landing elevation. Check the measurement in more than one place when the ground slopes.
Step 3: Calculate the number of risers
Use this simple process:
- Measure the total rise.
- Divide it by a trial riser height allowed by local code.
- Round to a whole number of risers.
- Divide the total rise by that whole number.
- Confirm the final riser height meets local limits.
Example
Suppose the total finished rise is 35 inches.
Dividing 35 by 7 gives 5. That creates five equal risers, each 7 inches high.
The example only shows the calculation. Your total rise and local maximum may differ.
The number of treads is often one fewer than the number of risers when the deck surface acts as the top tread. The actual connection and finish detail decide this, so draw the full side view before cutting.
Step 4: Choose the tread run
The tread depth must satisfy local code. The stringer run also needs to work with the tread boards, riser boards and required nosing.
For example, two deck boards with a gap may create a certain finished tread depth. That does not always equal the run marked on the stringer because the nosing can project beyond the riser face.
Check the decking manufacturer’s stair instructions. Composite and PVC boards may need much closer stringer spacing than wood. Some products have special limits for stair treads.
Step 5: Plan stringer size and spacing
Cut stringers are commonly made from suitable pressure-treated 2×12 lumber, but the approved plan controls material, grade, span and number.
Every notch removes wood. The remaining throat—the narrow section below the cuts—must remain strong enough. Do not use a smaller board simply because the staircase is short.
Stringer spacing depends on the tread material and design. Thick wood treads may span farther than some composite boards. Follow the exact decking installation guide rather than assuming 16-inch spacing is always acceptable.
Long stair runs may need intermediate support. Do not extend a cut stringer beyond the span allowed by the accepted design.
Step 6: Mark the first stringer
Use a framing square with stair gauges or an accurate rise-and-run template.
Mark the first rise and run near one end of the stringer. Continue the same pattern for the required number of steps. Keep the square or template firmly against the same board edge.
Then mark the top connection cut and bottom seat cut according to the approved detail.
The bottom of a cut stringer often needs an adjustment for tread thickness so every finished riser remains equal. The exact adjustment depends on how the top and bottom surfaces are detailed. Draw the finished surfaces before making this cut.
Step 7: Cut carefully
Support the lumber on a stable work surface. Wear eye and hearing protection and follow the tool manufacturer’s safety instructions.
Use a circular saw for the main cuts, but stop at the inside corner where the rise and run lines meet. Cutting past the corner weakens the stringer and can start a split.
Finish the corner with a jigsaw or handsaw. Do not force the circular-saw blade beyond the line.
Apply the field-cut treatment required by the pressure-treated lumber supplier. This is especially important at notches and exposed end grain.
Step 8: Test the first stringer
Place the first stringer in its planned position before using it as a template.
Check that:
- The top connection fits the deck frame.
- The bottom sits fully on the landing support.
- The stringer is level across each tread cut.
- The top and bottom finished risers will match the middle risers.
- The staircase has the correct angle and horizontal position.
- Tread boards and risers will fit as planned.
If the first stringer is wrong, correct the layout on a new board. Do not copy the error onto every remaining stringer.
Once the test is correct, trace it onto the other stringers. Use straight, suitable lumber and keep every pattern aligned with the same edge.
Step 9: Frame the top connection
Stringers need a positive structural connection to the deck. Do not rely only on toenails or screws driven through a thin rim board.
The stair opening may need a header, dropped support, blocking or approved stringer connectors. The exact detail depends on the frame and stringer position.
Use the connector model and fasteners shown in the approved plan. Joist-hanger nails, connector screws and ordinary deck screws are not interchangeable.
Install solid blocking for stair guard posts before access becomes difficult. Guard connections experience strong leverage and need support inside the deck framing.
Step 10: Support the bottom of the stairs
Stringers need full bearing on an approved landing or support. Soil, loose gravel and an ordinary thin patio slab may not provide a reliable foundation.
Local requirements may call for frost-depth footings, posts or a designed landing. The American Wood Council’s DCA 6 includes a specific stair-footing detail for projects within its limits.
Slope the surrounding grade so water does not remain against the bottom of the stringers. Keep wood out of direct soil contact unless the approved detail and treatment rating allow it.
Step 11: Install stringers, risers and treads
Set the outside stringers first, then position the inner stringers at the required spacing. Check that they are plumb, parallel and aligned.
Fasten each stringer with the specified connector and fasteners. Temporary bracing can help hold everything steady until the complete staircase is connected.
Install riser boards and treads in the order required by the chosen system. Maintain board gaps and end clearances according to the decking manufacturer.
Predrill when required, especially near board ends or when using dense hardwood. Do not overdrive fasteners. A screw driven too deep can damage the surface and weaken holding around the head.
Step 12: Add handrails, guards and lighting
Stair guards may be required when the open side is high enough above the ground. A handrail may be required based on the number of risers or local rule. These are separate safety parts.
The handrail should be continuous, graspable and installed at the required height. Guard openings and the triangular area beside the treads must meet applicable limits.
Do not assume a deck-level railing kit automatically fits stairs. Stair angle changes rail length, post spacing, brackets and baluster cuts. Follow the exact railing instructions.
Outdoor stairs also need lighting where required. Plan wiring before treads and trim hide the route. Electrical work may need a separate permit.
Deck Building 101: A Homeowner’s Planning Guide
Common deck stair mistakes
Unequal riser heights
This often happens when tread or landing thickness is added after the calculation. Measure between finished surfaces and check the top and bottom steps carefully.
Overcut stringer corners
Running a circular saw past the inside corner removes important wood. Stop at the line and finish the cut with another saw.
Too few stringers
Treads can flex or fail when supports are too far apart. Use spacing required by the exact tread product.
Weak top attachment
Toenails or ordinary screws may not provide an approved connection. Use proper framing, connectors and listed fasteners.
Poor bottom support
Stringers resting on soil or a moving slab can settle and change the first riser.
Forgetting guard-post blocking
Adding posts after the stairs are finished can lead to weak attachments. Plan blocking and hardware with the stair frame.
Copying dimensions from another deck
Total rise, local code, tread material and landing height are project-specific. Recalculate every staircase.
A short installation checklist
Before final inspection, confirm that:
- Total rise was measured between finished surfaces.
- Every riser and tread meets the approved dimensions.
- Stringer lumber, spacing and span match the plan and tread instructions.
- Cuts stop at the marked corners.
- Field cuts received required treatment.
- Stringers have approved top connectors and solid bottom bearing.
- The landing is stable, level and properly drained.
- Treads and risers use approved fasteners and gaps.
- Handrails, guards, posts and openings meet local requirements.
- Lighting and electrical work are complete where required.
- Required inspections are approved.
Frequently asked questions
How many stringers do deck stairs need?
It depends on stair width, stringer span and the tread manufacturer’s maximum support spacing. Composite boards often require closer spacing than wood.
What lumber is used for deck stair stringers?
Cut stringers are commonly made from suitable pressure-treated 2×12 lumber. Confirm species, grade, treatment and dimensions with the approved design.
How do I keep every stair rise equal?
Measure from the finished deck to the finished landing, divide by a whole number of risers, and adjust the top and bottom cuts for the actual tread and landing details.
Can stringers rest on a concrete patio?
Only when the concrete is accepted as suitable support. A thin slab may move with frost or crack under load. Follow the approved landing and footing detail.
Should I cut all stringers together?
No. Cut and test one stringer first. Once it fits correctly, use it as the pattern for the others.
Do deck stairs need a handrail?
Often, yes, once the stair has the number of risers stated by local code. Confirm the trigger, height, grip shape and continuity with the building department.
Final thoughts
Good deck stairs begin with one accurate measurement: the distance between the finished deck and finished landing. From there, divide the rise evenly, match the tread layout, and test one stringer before cutting the rest.
Give special attention to the top connection, bottom support, stringer spacing, guards and handrails. Follow approved plans, local building requirements and the current instructions for lumber, decking, connectors, fasteners and railing.
Shortcuts are easy to see in stairs because every step repeats the same detail. Careful layout makes them safer, more comfortable and easier to finish.
Research sources
- International Code Council: Residential Stairway Requirements
- American Wood Council: Prescriptive Residential Wood Deck Construction Guide
- Simpson Strong-Tie: Deck Connection and Fastening Guide
- Trex: How to Build Deck Stairs
- 811: Before You Dig