How to Install Deck Stair Railings and Handrails
Stair railings provide critical safety support when navigating stairs. Unlike flat deck railings, stair railings must follow the angle of the stairs and feature a graspable handrail that you can actually hold onto. This final railing step ensures your deck stairs are both safe and code-compliant.
Quick Summary
2-4 hours
Moderate
$100-300 (materials)
Stair Railings vs. Deck Railings: Key Differences
Stair railings have different requirements than the flat railings around your deck perimeter:
| Requirement | Deck Railing | Stair Railing |
|---|---|---|
| Height | 36-42" from deck surface | 34-38" from stair nose |
| Orientation | Horizontal (level) | Angled (follows stair slope) |
| Graspable handrail | Not required | Required (1.25-2" diameter) |
| Returns | Not required | Required at ends |
Understanding Graspable Handrails
Building codes require stair handrails to be graspable—meaning you can wrap your fingers around them for a secure grip. A flat 2x4 or 2x6 board does NOT meet this requirement, even though it's commonly used for deck top rails.
Graspable handrail requirements:
- Circular cross-section: 1.25 to 2 inches diameter
- Non-circular: Perimeter between 4 and 6.25 inches with max cross-section of 2.25 inches
- Continuous grip: No breaks or obstructions along the gripping surface
- Finger clearance: At least 1.5 inches between handrail and wall or post
Pro Tip: Buy purpose-made handrail stock from a building supply store. It comes pre-shaped with the right profile, often with a flat bottom for easy mounting. Trying to shape your own graspable rail is time-consuming and difficult to get right.
Materials and Tools
Materials
- Graspable handrail stock – wood or composite, 1.5" diameter or similar profile
- 4x4 posts – for top and bottom of stairs (if not already installed)
- Handrail brackets – metal or decorative mounting hardware
- Returns – curved pieces that terminate handrail into wall/post
- Rail bolts – for connecting handrail sections to returns
- Structural screws – 3-inch for mounting brackets
Tools
- Miter saw – essential for angle cuts on handrail
- Angle finder or bevel gauge – to determine stair angle
- Drill/driver – for mounting brackets and driving screws
- Level – for checking post plumb
- Tape measure – for measuring heights and lengths
- Pencil – for marking bracket positions
Step-by-Step Installation
Step 1: Install or Verify Stair Posts
Stair railings need sturdy posts at top and bottom of the stairs:
- Top post typically mounts to deck rim joist or last stair stringer
- Bottom post attaches to stringer base or landing
- Use same bolting method as deck railing posts (carriage bolts)
- Verify posts are plumb in both directions
Step 2: Determine Handrail Angle
The handrail must be parallel to the stair slope. Find the angle:
- 1.Place a straight board across several tread nosings
- 2.Use an angle finder to read the angle against horizontal
- 3.Note this angle—typically 32-38 degrees for residential stairs
- 4.Your miter cuts will use this angle (or its complement)
Step 3: Mark Handrail Height on Posts
Measure handrail height from the stair nose, NOT from the tread surface:
- Required height: 34-38 inches above stair nose
- 36 inches is a good middle-ground height
- Measure vertically from the nose of the nearest tread to each post
- Mark this height on both posts
Important: Stair handrail height is measured differently than deck railing height. Deck railings are measured from the deck surface. Stair handrails are measured from the front edge of each tread (the nose). This ensures consistent hand position as you climb.
Step 4: Measure and Cut Handrail
Measuring angled railings requires careful technique:
- 1.Stretch a string between your marked heights on each post
- 2.Measure the distance along the string (this is your rail length)
- 3.Set miter saw to your stair angle
- 4.Cut both ends at this angle, parallel to each other (not opposing)
- 5.Test fit before final installation
Step 5: Install Handrail Brackets
Handrail brackets mount to the posts and support the rail:
- Position brackets at your marked heights
- Ensure at least 1.5 inches clearance between rail and post
- Pre-drill and secure with appropriate screws
- For longer runs, add intermediate brackets every 4 feet
Step 6: Mount Handrail
Attach the handrail to the brackets:
- 1.Set handrail into brackets
- 2.Check that rail follows stair angle evenly
- 3.Secure with screws through bracket into underside of rail
- 4.Verify rail is at consistent height above treads along entire run
Step 7: Install Returns
Handrails must terminate safely—they cannot end in open space:
- Post-mounted returns: Curved piece turns handrail back to post
- Wall returns: Rail curves back to wall if stairs are against house
- Volutes or rosettes: Decorative terminations that satisfy code
Connect returns using rail bolts (specialized fasteners that pull pieces together) or construction adhesive and screws.
Adding Balusters to Stair Railings
If your stair railing includes infill balusters (not just a standalone handrail), the same 4-inch sphere rule applies:
- Maximum 4-inch gap between balusters
- The triangular space above each tread cannot allow 4-inch sphere
- Balusters are cut at angle matching stair slope
- Or balusters sit plumb with angled bottom cuts to match stair slope
Common Mistakes to Avoid
Using Non-Graspable Top Rail as Handrail
A flat 2x4 or 2x6 board is not graspable and doesn't meet code for stair handrails. You need purpose-made handrail stock with a round or shaped profile that allows a full grip.
Measuring Height from Tread Surface Instead of Nose
Stair handrail height is measured from the front edge of the tread (the nose), not the tread surface. Measuring from the surface results in a rail that's too high at the back of each step.
Leaving Handrail Ends Exposed
Handrails that end in open space catch clothing and can cause falls. Always terminate with returns to a wall, post, or with decorative volutes that satisfy code requirements.
Insufficient Finger Clearance
If the handrail is mounted too close to the post or wall, you can't get a proper grip. Maintain at least 1.5 inches of clearance between the rail and any adjacent surface.
FAQ
What is the required height for stair handrails?
Stair handrails must be between 34 and 38 inches high, measured vertically from the stair nose (front edge of tread) to the top of the handrail. This is different from deck railings which are measured from the deck surface.
What makes a handrail graspable?
A graspable handrail must be sized so you can wrap your fingers around it. Building code requires a circular diameter between 1.25 and 2 inches, or a non-circular shape with perimeter between 4 and 6.25 inches. Standard 2x4 lumber is NOT graspable.
Do stair railings need returns?
Yes, handrails must terminate in a way that won't snag clothing. This means returning to a wall, returning to a post, or terminating in a newel post or volute. The handrail cannot simply end in open space.
What angle should stair railings be installed at?
Stair railings should be installed parallel to the slope of the stairs—following the same angle as a line drawn across the tread nosings. Use an angle finder on the stringers or treads to determine the exact angle.