Stair stringers for a 2 ft (24 in) high deck
A 2 ft (24 in) high deck needs 4 risers of 6 inches and 3 treads — not three 8 inch steps. At 10½ inch treads the run is 31-1/2 inches (2 ft 7-1/2 in) and each stringer is about 39-5/8 inches (3 ft 3-5/8 in) long.
How to work it out
- 24 in ÷ 7.75 in max = 3.1 → round up to 4 risers, each 24 in ÷ 4 = 6 in
- 3 treads × 10-1/2 in = 31-1/2 in run · √(24² + 31.5²) = 39-5/8 in along the slope
- Comfort check: 2 × 6 in + 10-1/2 in = 22.5 in (24–26 in is comfortable) · stair angle 29.7 degrees
- Throat: 11-1/4 in board − 5.21 in notch depth = 6-1/16 in
- Tread board: 10-1/2 in tread + 3/4 in nosing + 0 in riser board = 11-1/4 in
- Top level cut: 6 in riser + 1 in tread = 7 in below the deck surface
Low decks catch people out: 24 ÷ 7¾ is 3.1, so three 8 in steps are over the limit and the flight goes to four gentle 6 in risers. That adds a tread and pushes the bottom step about 2½ ft out from the deck.
Six-inch risers feel best with a deeper tread. With 10½ in treads, 2 × riser + tread is only 22½ in; if you have the room, try 11–12 in treads and watch the comfort figure climb toward 24 in.
Adjust for your project
More options: Max riser · Spacing · Stringer board …
- Steps to cut
- 3 steps to cut in each stringer + the deck is the top step
- Total run (how far the stairs reach out)
- 31-1/2 in (2 ft 7-1/2 in)
- Stringer length (along the slope)
- 39-5/8 in (3 ft 3-5/8 in)
- Stringers needed
- 4 stringers
- Stringer stock to buy
- 4 × 2×12 × 8 ft
- Tread board depth to buy (tread + nosing + riser board)
- 11-1/4 in
- Drop the stringer (trim off the bottom)
- 1 in
- Top level cut, measured down from the top surface
- 7 in
- Wood left below the notches (throat)
- 6-1/16 in
| Item | What to buy | Notes |
|---|---|---|
| Stringers | 4 × 2×12 × 8 ft | Pressure-treated and rated for ground contact (check the end tag) — the bottoms sit near the ground. |
| Treads | 6 pieces 36 in long (2 per step) → buy 2 × 5/4×6 × 10 ft | 2 boards 5½ in wide with ¼ in gaps cover 11-1/4 in of the 11-1/4 in each step needs; 3 pieces per 10 ft board. |
| Hardware | Sloped joist hangers or a hanger board at the top (DCA 6 Fig. 31); screws or nails rated for treated lumber (hot-dip galvanized or stainless) | Plus a handrail on at least one side — four or more risers (2021 IRC R311.7.8). |
Where to mark each step (height above the bottom)
| Step | Height above the bottom | Guard on open sides? |
|---|---|---|
| Tread 1 | 6 in | — |
| Tread 2 | 12 in | — |
| Tread 3 | 18 in | — |
| Deck surface | 24 in | — |
One step fewer or more
| Risers | Each step | Treads | Tread depth | Total run | Check |
|---|---|---|---|---|---|
| 3 risers | 8 in | 2 | 10-1/2 in | 21 in | Risers too tall |
| 4 risers (shown) | 6 in | 3 | 10-1/2 in | 31-1/2 in | OK |
| 5 risers | 4-13/16 in | 4 | 10-1/2 in | 42 in | OK |
- 2 × riser + tread is 22.5 in, outside the 24–26 in most people find comfortable. Deeper treads help. (A comfort guide, not a code rule.)
- The 4 stringers come from the 16 in default spacing — the joist spacing 5/4 wood decking needs on a deck (2021 IRC Table R507.7). DCA 6 allows cut stringers up to 18 in apart — 3 for this width — if your tread boards are rated for that span (check the tread maker).
- What the bottom sits on: DCA 6 doesn’t let deck stringers bear on a pad or patio that isn’t founded below frost depth — set them on posts or footings. See what the bottom of the stringers sits on.
- Leave a landing at the bottom at least 36 in deep and as wide as the stair (IRC R311.7.6); the deck is the top landing.
- Trim 1 in off the bottom of each stringer (one tread thickness) so the first step comes out the same 6 in as the rest.
Risers for a 24 in rise, by maximum riser height
| Maximum riser | Step-ups (risers) | Riser height (decimal) | Total run (how far the stairs reach out) | Stringer length (along the slope) |
|---|---|---|---|---|
| 7 in | 4 risers | 6 in | 31-1/2 in (2 ft 7-1/2 in) | 39-5/8 in (3 ft 3-5/8 in) |
| 7.5 in | 4 risers | 6 in | 31-1/2 in (2 ft 7-1/2 in) | 39-5/8 in (3 ft 3-5/8 in) |
| 7.75 in | 4 risers | 6 in | 31-1/2 in (2 ft 7-1/2 in) | 39-5/8 in (3 ft 3-5/8 in) |
| 8 in | 3 risers | 8 in | 21 in | 31-7/8 in (2 ft 7-7/8 in) |
What to know about stairs for a 2 ft deck
Four risers is exactly the count at which IRC R311.7.8 starts requiring a handrail on at least one side, mounted 34–38 in above the nosings — so even this short flight needs one. A deck surface 24 in up is under the 30 in guard trigger in R312.1.1, as long as the ground within 36 in of the edge doesn’t drop lower, so code does not demand a guard at this height; you can still add one.
The 8 in trap: three risers of 8 in would save a tread and some yard, but 8 in is over the 7¾ in maximum in R311.7.5.1. The ⅜ in rule in the same section bites here as well. If the landing pad ends up lower than planned, only the bottom riser grows, and once it is more than ⅜ in taller than the other three the flight fails even though the average looks fine.
Stringers this short are forgiving. Each is only about 40 in long, and a 2×12 keeps a generous 6 in of throat below the notches. Two stringers often come out of one 8 ft board, so the four stringers for a 36 in wide stair can come from two boards rather than the four the stock line lists — lay both on the board before you cut.
To see how the count grows, compare How many steps for a 30 in deck, still four risers but 7½ in tall, How many steps for a 3 ft deck and How many steps for a 4 ft deck; indoors, Stair stringers for an 8 ft rise runs to thirteen risers.
Different size? Use the full Stair Stringer Calculator.
What you’ll need
- Framing squareBudget price
The tool for laying out stair stringers and rafters: rise on one leg, run on the other.
See options on Amazon (opens in a new tab) - Stair gaugesBudget price
Small brass or steel buttons that clamp to a framing square so every rise and run you mark is identical.
See options on Amazon (opens in a new tab) - Circular saw (7¼ in)Mid-range price
The most versatile first power saw: crosscuts framing lumber, rips boards and, with a straightedge, breaks down plywood sheets.
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Frequently asked questions
Can 24 in deck steps be three 8 in risers instead of four?
The arithmetic works — 3 risers of 8 inches and 2 treads with 21 inches of run — but 8 inches is over the IRC’s 7¾ inch maximum riser (R311.7.5.1), so it would fail inspection. Keep four risers.
How long are the stringers for 24 in steps with 12 in treads?
About 43-1/4 inches (3 ft 7-1/4 in) each, with 36 inches (3 ft) of run. Deeper treads suit 6 inch risers: 2 × riser + tread comes to 24 in, the bottom of the comfortable 24–26 in range.
Other common sizes
- How many steps for a 3 ft deck — 5 risers
- How many steps for a 30 in deck — 4 risers
- How many steps for a 4 ft deck — 7 risers
- Stair stringers for an 8 ft rise — 13 risers
- Stair stringers for a 2.7 m rise — 15 risers
Sources
- International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (opens in a new tab) — R311.7.1 width (36 in), R311.7.2 headroom (6 ft 8 in), R311.7.3 vertical rise of a flight (12 ft 7 in), R311.7.5.1 risers (7¾ in; open risers more than 30 in up must not pass a 4 in sphere), R311.7.5.2 treads (10 in), R311.7.5.3 nosings (¾–1¼ in unless the tread is 11 in or deeper), R311.7.6 landings (36 in deep), R311.7.8 handrails, R312.1 guards.
- American Wood Council, DCA 6 Prescriptive Residential Wood Deck Construction Guide (2015 IRC edition) (opens in a new tab) — Stair requirements, Figures 28, 29, 31 and 34: 2×12 minimum stringers; cut stringers span no more than 6 ft 0 in and keep at least 5 in below the notches; at least three cut stringers at no more than 18 in on center; sloped hangers or a hanger board at the top; an intermediate landing where the total rise exceeds 12 ft; stringers bear on footings below frost depth, not on pads or patios that aren’t founded that deep.