Do stairs need handrails on both sides?

IRC R311.7.8.2 — only if stair is WIDER than 44″. Below 44″ (which covers most residential 36-42″ stairs): one-side handrail is fine + code-compliant. Above 44″ (rare for residential): BOTH sides required. The calculator forces both-sides automatically when stair width exceeds 44″.

What's the IRC handrail height?

34-38″ measured vertically from the tread nose (R311.7.8.1). 36″ is most common — comfortable for adults. 34″ for shorter users or kid-friendly stairs. 38″ is the max — anything higher violates code. The handrail must be continuous along the stair flight (no breaks).

Is a guardrail different from a handrail?

Yes. Handrail = the gripping rail people hold (single horizontal rail, 34-38″ height). Guardrail = the full balustrade system (top rail + balusters + posts, 36-42″ height typically). On stairs over 30″ off grade, you typically need BOTH (R312.1 + R311.7.8). The Calculator separates the two cost lines.

How much does stair railing cost?

Wildly varies by material. For a 5-step stair (80″ run, 49″ rise, ~8 ft sloped length): PT pine handrail + guardrail = ~$320 ($40/LF combined). Cedar = $480. Composite (Trex matching) = $620. Aluminum = $930. Cable = $1,140. Cable is most expensive but gives unobstructed view.

When do I need a guardrail on stairs?

IRC R312.1 — required if the stair walking surface is more than 30″ above grade. Even one step might require it if that step is above 30″ off ground (rare but possible on hillside decks). Below 30″ off grade: handrail only is fine. Above 30″: full guardrail required to prevent falls off the side.

What material for stair railing?

Match the deck railing material. Trex deck = Trex handrail + Transcend balusters. Composite deck = matching composite. Cedar deck = cedar railing. Mismatched materials look DIY. Premium upgrade: cable rail anywhere because it gives unobstructed view — best aesthetic, highest cost ($48-95/LF).

Can I add a cable rail on stairs?

Yes — cable rail works on stairs but requires specific stair-rated brackets that allow the cable to angle along the stair slope. Premium choice — ~$48/LF handrail + $95/LF full cable railing system. The Cable Railing Calculator has stair-specific math (cable spacing tightens to ≤4″ at stair triangle per R311.7.8.2.2). For unobstructed views from stairs, nothing beats cable.

Does stair railing height differ from deck railing?

Yes. Deck guardrail = 36″ minimum (R312.2). Stair handrail = 34-38″ (R311.7.8.1). The two MUST transition smoothly where stairs meet deck — typically the deck guardrail steps down from 36″ to 38″ at the stair top, then the 34-38″ handrail follows the stair flight. Most installers run the handrail at 36″ from tread nose for consistency with deck height.

How do I attach handrails to a stair?

Two paths: (1) Newel posts at the bottom + top of stair — handrail runs between them. (2) Wall-mounted brackets (Simpson StairTek or similar) — handrail attaches to adjacent wall. Most residential decks use newel posts. The handrail must support 200 lb in any direction per IRC R311.7.8.4 — translates to 8-10 brackets/posts for a typical stair flight.

Stair · IRC R311.7.8 + R312 railings

Stair Railing Calculator

Stair handrail + guardrail sizing across 6 materials (PT pine, cedar, composite, aluminum, steel, cable). Pythagorean sloped length × auto-both-sides for stairs over 44″ wide (IRC R311.7.8.2). Handrail height check (R311.7.8.1, 34-38″). Optional guardrail (R312.1, required if walking surface > 30″ off grade).

IRC R311.7.8 + R3126 materialsAuto both-sides

34-38″·Handrail height

44″·Both-sides threshold

√·Pythagorean length

6·Materials

Inputs

Stair runft

Stair risein

Stair widthft (>44″ forces both sides)

Handrail height (IRC 34-38″)

Material

Both sides + guardrail

Stair railing · pt pine

$3207.82ft sloped × 1 side

Sloped length

Pythagorean from rise+run

Handrail LF

1 side

Handrail cost

$12/lf

Total + guard

+$224 guardrail

IRC R311.7.8 + R312 compliance

Handrail 34″ — IRC compliant

IRC R311.7.8.1

Within IRC R311.7.8.1 range. Measure vertically from tread nose at every step.

8 lf handrail × $12/lf = $96

2026-Q1 retail

Sloped length 7.82 ft × 1 side. pt pine pricing.

8 lf guardrail × $28/lf = $224

IRC R312.1

Full balustrade system (top rail + balusters + posts) follows handrail path. Required if walking surface > 30″ off grade per IRC R312.1.

IRC R311.7.8.1 handrail height 34-38″. R311.7.8.2 both sides if stair >44″. R312.1 guardrail required if >30″ off grade. Pair with Railing Cost + Cable Railing + Baluster Spacing Calculators.

How to use

How to use the deck calculator in 3 steps.

Enter stair run + rise

Total run in ft (horizontal stair length). Total rise in inches (grade to deck top). These feed Pythagoras for sloped length.

Set stair width

If > 44″ (3.67 ft), IRC R311.7.8.2 REQUIRES handrails on BOTH sides — the calculator forces both-sides automatically. Below 44″, one-side is allowed (toggle the both-sides option for design preference).

Pick handrail height

IRC R311.7.8.1: 34-38″ measured vertically from tread nose. 36″ is most common. 34″ for shorter users. 38″ for taller. Above 38″ = code violation.

Pick material

PT pine ($12/LF). Cedar ($18). Composite ($26 — matches deck). Aluminum ($38 — modern). Steel ($32 — industrial). Cable ($48 — minimalist, premium).

Include guardrail if needed

IRC R312.1 — guardrail (full balustrade) required if stair walking surface is >30″ off grade. The calculator adds guardrail cost ($28-95/LF depending on material) on top of handrail cost.

How we calculate

How DeckMath calculates the result — IRC 2021 sources.

The Stair Railing Calculator sizes handrails + guardrails for stairs per IRC R311.7.8 + R312. Pythagorean sloped length × handrail count (1 or 2 sides per IRC R311.7.8.2 — both sides if stair >44″ wide). 6 materials (PT pine, cedar, composite, aluminum, steel, cable) × handrail-only vs handrail+guardrail. Auto-enforces IRC handrail height 34-38″ + handrail-both-sides threshold. Guardrail required separately if stair walking surface >30″ off grade (R312.1).

IRC references

IRC R311.7.8.1 — Handrail height 34-38″
IRC R311.7.8.2 — Both sides if stair > 44″ wide
IRC R312.1 — Guardrail at > 30″ off grade
IRC R311.7.8.3 — Grip dimensions Type I or II

IRC 2021 R311.7.8 + R312. Material pricing 2026-Q1 big-box retail.

Sloped length

sloped = √(run² + rise²) / 12 (convert to ft)

Same Pythagorean math as stringer length. For 80″ run × 49″ rise: √(6400 + 2401) = 93.8″ = 7.82 ft sloped length per handrail.

Total handrail LF

total = sloped × handrail_count

1 side or 2 sides. For 7.82 ft × 2 sides = 15.6 ft total — round to 16 ft for ordering.

Handrail cost

cost = total_lf × $/LF

PT pine: 16 × $12 = $192. Aluminum: 16 × $38 = $608. Cable: 16 × $48 = $768 for handrail only.

Guardrail (R312.1)

guardrail_lf = sloped × handrail_count (matches handrail)

Full balustrade follows the same path as handrail. Cost: PT pine $28/LF, aluminum $78/LF, cable $95/LF. Required if stair walking surface > 30″ off grade.

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Deck calculator questions, answered.

Deck Railing Cost Calculator

Installed railing cost across 8 systems: PT, cedar, composite (Trex/TimberTech), PVC (AZEK), cable (Feeney), glass, aluminum (Westbury), steel. 3 styles each, brand-matched kits, DIY vs contractor.

Cable Railing Calculator

Stainless cable railing — 11 cables @ 36″ guard, tension load on end posts, post spacing 4-6′ by diameter. 5 brands (Feeney, Atlantis, Ultra-tec, Viewrail, generic) × 3 diameters × 4 substrates. IRC R312.

Deck Stair Calculator

Risers, treads, stringer hypotenuse, and BoM for any deck height — IRC 2021 R311.7 compliant with auto handrail + landing-pad sizing.