How to Install Deck Stair Treads and Risers
With your stringers cut and installed, it's time to add the walking surface. Stair treads take more abuse than any other part of your deck—they endure foot traffic, weather exposure, and the stress of people stepping down. Proper installation ensures safe, solid footing for years to come.
Quick Summary
1-2 hours
Easy
$75-200 (materials)
Understanding Tread Anatomy
A stair tread has specific parts that affect both appearance and safety:
- Tread: The horizontal surface you step on. Usually two 2x6 boards or a single wide stair tread board.
- Nosing: The front edge of the tread that extends past the riser below. Provides a visual cue and solid footing when descending.
- Riser: The vertical board between treads (optional on deck stairs). Closes off the step for a finished look.
- Overhang: How far the tread extends past the outside stringers on each side. Usually about 1 inch.
Materials and Tools
Materials
- 2x6 or 5/4x6 deck boards – two per step for standard tread depth
- Pre-made stair treads (alternative) – single wide boards with bullnose edge
- 1x8 boards for risers (optional) – if installing closed risers
- 3-inch deck screws – coated or stainless for treated lumber
- Construction adhesive (optional) – for squeak-free treads
Tools
- Miter saw or circular saw – for cutting treads to length
- Drill/driver – for pre-drilling and driving screws
- Tape measure – for measuring tread lengths
- Speed square – for marking square cuts
- Spacers – for consistent gap between tread boards
- Router with roundover bit (optional) – for bullnose nosing edge
Tread Options
You have two main approaches for building stair treads:
| Option | Pros | Cons |
|---|---|---|
| Two 2x6 boards | Matches deck, drainage gap, affordable | Visible gap, requires nosing on front board |
| Pre-made stair treads | Solid surface, bullnose included, cleaner look | More expensive, may not match decking exactly |
| Composite stair treads | Matches composite deck, low maintenance | Highest cost, follows manufacturer specs |
Step-by-Step Installation
Step 1: Measure and Cut Treads
Calculate tread length based on stair width plus overhangs:
- Measure distance between outside faces of outer stringers
- Add 2 inches for 1-inch overhang on each side
- Cut all treads to this length for consistency
Step 2: Round Over Nosing Edge (Recommended)
The front board of each tread should have a rounded nosing for comfort and safety:
- Use router with 1/4" or 3/8" roundover bit on front edge
- Also round the top edges of the ends
- Alternative: buy pre-milled bullnose boards or stair treads
Step 3: Position Front Tread Board
Start with the bottom step and work up:
- 1.Place front board with rounded edge facing forward
- 2.Extend nosing 1 to 1.5 inches past stringer face (where riser would go)
- 3.Center board so overhangs on each side are equal
- 4.Check that board is square to stringers
Step 4: Secure Front Board
Fasten the front tread board to each stringer:
- 1.Apply construction adhesive to stringer tops (optional but reduces squeaks)
- 2.Pre-drill two holes at each stringer location (about 1" from edges)
- 3.Drive 3-inch deck screws, countersinking slightly
- 4.Don't overtighten—flush with surface is ideal
Pro Tip: Pre-drilling is essential for stair treads. The wood is usually pressure-treated and hard, and screws near board ends will split the wood without pilot holes. Use a countersink bit to recess screw heads slightly.
Step 5: Add Second Tread Board
If using two boards per tread (typical with 2x6):
- Position back board against the riser cut of the stringer
- Leave 1/8" to 1/4" gap between boards for drainage
- Use spacers for consistent gaps across all steps
- Pre-drill and secure with same screw pattern
Step 6: Repeat for All Steps
Work your way up the stairs:
- Maintain consistent nosing overhang on each step (1-1.5 inches)
- Keep board gaps consistent
- Check that treads are level side-to-side
- Sight down stairs to check alignment
Installing Risers (Optional)
Risers are optional on deck stairs but add a finished look and prevent debris from collecting underneath. If you choose to install risers:
- 1.Measure height: Measure from top of each tread to bottom of the one above
- 2.Cut 1x8 boards: Rip to measured height if needed
- 3.Position against stringer faces: Riser fits in the vertical notch
- 4.Secure with screws: Drive through stringer into riser edge, or through tread into riser top
Note: If leaving risers open, ensure the opening between tread and the step below doesn't allow a 4-inch sphere to pass through. This typically isn't an issue with standard tread depth but verify if you have shallow treads.
Common Mistakes to Avoid
Inconsistent Nosing Overhang
Varying nosing depths make stairs feel awkward and can be a trip hazard. Use a spacer or jig to maintain exactly the same overhang on every step.
Excessive Nosing Projection
Nosing that extends more than 1.5 inches past the riser catches heels when ascending. Building code limits nosing to 1.5 inches maximum. Stick to 1 to 1.25 inches for safety.
Skipping Pre-Drilling
Driving screws near board ends without pilot holes splits the wood, weakening the connection and looking unprofessional. Always pre-drill, especially in treated lumber.
Not Matching Decking Material
Using different wood species or composite brands on stairs vs. deck creates a mismatched appearance. Use the same material for a cohesive look throughout.
Quality Check
After installing all treads, verify your work:
- Walk the stairs: Each step should feel solid with no bounce or flex
- Check nosing: Consistent 1-1.5 inch projection on all treads
- Verify gaps: Consistent spacing between boards across all steps
- Check alignment: Sight down stairs—all treads should align
- Test for squeaks: Bounce on each step—no noise means good connection
FAQ
How much should stair treads overhang the stringers?
Stair treads should overhang the outside stringers by about 1 inch on each side for a finished look. The nosing (front edge) should extend 1 to 1.5 inches beyond the riser below. Total nosing projection should not exceed 1.5 inches.
Do deck stairs require risers?
Most building codes do not require risers on deck stairs. Open risers are allowed as long as the opening doesn't permit a 4-inch sphere to pass through. However, risers add a finished look and prevent debris from collecting under stairs.
What is the best material for stair treads?
For durability, use the same material as your decking—pressure-treated 2x6 or 5/4x6 boards for wood decks, or composite stair treads for composite decks. Matching materials provide a cohesive look.
How many screws per tread on each stringer?
Use two screws per board at each stringer location. For a typical 36-inch wide stair with three stringers, that's six screws per tread board. Pre-drill to prevent splitting, especially near board ends.