DeckMath
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Animated educational guide

How are deck stairs built?

Watch the 4-phase build sequence: stringers cut → risers stack → treads land → handrail assembles. Each phase has cost, tools, DIY difficulty, and the most common mistake pros make. IRC R311.7 specs labeled.

gradedeck
Phase 0/5Initial
StartStriRiseTreaHandSett

Phase-by-phase breakdown

Total cost for a typical 5-step stair: $410-1,290 material + labor. DIY-friendly for skill level 2+ on phases 2-3; phases 1 and 4 need experience.

1

Cut stringers

$50-95DIY 4/5

PT 2×12 lumber cut with rise/run notches. Most critical step — a wrong stringer ruins every step above it.

Tools:Framing square, circular saw, speed square, pencil
Common mistake: Cutting only 2 stringers for a wide stair (>36″). IRC requires 3 stringers when stair width is 36-48″.
2

Install risers

$30-65DIY 2/5

Vertical face boards between treads. Match decking material. Install bottom-to-top, level each.

Tools:Drill, deck screws, level
Common mistake: Forgetting that risers + tread thickness must equal exactly the unit rise (7-7.75″). Off by 1/4″ = trips waiting to happen.
3

Install treads

$110-450DIY 2/5

Horizontal boards you step on. Match decking material. 4-6″ overhang allowed; rounded nose preferred.

Tools:Drill, deck screws (or hidden fasteners for composite), miter saw
Common mistake: Not pre-drilling pilot holes on hardwood (IPE) treads. Splits the wood and ruins the look.
4

Build handrail

$220-680DIY 4/5

IRC R311.7.8 requires handrail 34-38″ above tread nosing, full stair run. Must extend to landing.

Tools:Drill, level, square, post-mount hardware
Common mistake: Skipping the handrail return (the 90° turn at the top/bottom). IRC R311.7.8.3 mandates returns to prevent clothing snag.
Size your stair
Get rise/run + stringer math →

Deck Stair Calculator returns exact riser height, tread depth, stringer length, and stringer count for IRC compliance.

Open Stair Calculator
Handrail design
Verify IRC R311.7.8 compliance →

Handrail Calculator validates Type 1 grip, 34-38″ height, returns, and full ADA 505 mode. 7 materials × 4 mount styles.

Open Handrail Calculator

What this tells you

  • ✓ What pieces a deck stair is built from (4 components)
  • ✓ What order pros assemble them in
  • ✓ How IRC R311.7 specs (rise/tread/handrail) apply at each step
  • ✓ The most common mistake at each phase

What it doesn't tell you

  • — Exact stair dimensions for your deck — use the Deck Stair Calc
  • — How many stringers needed for your stair width — use Stair Calc
  • — Total material cost — use Stair Calc + Handrail Calc combined
  • — Code variations in your jurisdiction (some require curved-nose treads)

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IRC code reference

  • • IRC 2021 R311.7.5.1 — Max riser 7.75″, min tread 10″ (consistent within ⅜″ across all steps)
  • • IRC 2021 R311.7.8 — Handrail 34-38″ above tread nosing, full stair run, returns at top + bottom
  • • IRC 2021 R311.7.3 — Landing required every 12 ft of vertical rise
  • • IRC 2021 R311.7.2 — Stair width minimum 36″ above handrail (with handrail: 31.5″ clear)