Published August 13, 2026 · Updated August 23, 2026 · By Tupep
Two elevations decide everything
A deck stair goes wrong in two places, and both are at the ends. At the bottom, people measure total rise to the dirt instead of to the finished landing that has not been poured yet. At the top, they forget that the stringer bears against the deck framing while the walking surface is the decking sitting on top of it. Both mistakes produce the same symptom: one riser different from all the others, which is the most common trip hazard and the most common inspection failure.
Get the total rise right first
Total rise = top of the finished deck surface minus top of the finished landing. Not grade, not the gravel.
Example: the deck surface is 48 in above existing grade. The landing will be a 4 in concrete pad over compacted gravel, set so its top sits 2 in above surrounding grade for drainage. Landing top is grade + 2, so total rise is 48 minus 2 = 46 in.
That is why we set pad elevation before cutting stringers. Pour it first, or at minimum stake and string the finished elevation so the number is real. Pouring afterward to whatever height works is how you get a 5 in bottom riser.
| Risers | Riser height | Treads | Total run at 11 in | Comment |
|---|---|---|---|---|
| 5 | 9.200 in | 4 | 44 in | Far above common limits |
| 6 | 7.667 in | 5 | 55 in | Typical choice, check against your local max |
| 7 | 6.571 in | 6 | 66 in | Easier walk, needs 11 more inches of yard |
| 8 | 5.750 in | 7 | 77 in | Gentle, long footprint |
Maximum riser height, minimum tread depth, nosing requirements, the allowable variation between risers in one flight, handrail requirements and guard heights are all jurisdiction dependent. Many residential codes cap risers somewhere around 7-3/4 in and require a handrail once a flight reaches about four risers, but verify every one of those with your building department rather than trusting a number off the internet.
Dropping the stringer at the bottom
Lay out the sawtooth with six equal 7.667 in rises and five 11 in runs. Cut it that way and sit it on the pad, and the first tread sits on top of the first cut, so the bottom riser becomes 7.667 plus the tread thickness, 1.5 in taller than all the others.
The fix is called dropping the stringer: reduce the bottom horizontal cut by exactly one tread thickness. With 2x tread material at 1.5 in actual, the bottom cut drops 1.5 in. Now the first cut surface sits at 6.167 in, the tread makes the walking surface 7.667 in, and every riser matches.
Verify the stack. Cut surfaces land at 6.167, 13.833, 21.5, 29.167 and 36.833 in above the pad. Add 1.5 in of tread and walking surfaces are 7.667, 15.333, 23.0, 30.667 and 38.333, exactly 1 through 5 times 7.667. The sixth riser is the deck surface at 46 in.
The top: decking thickness versus tread thickness
Now look at the stringer’s top plumb cut. With the bottom dropped 1.5 in, the top of the stringer sits at 46 minus 1.5 = 44.5 in above the pad. But the deck framing top, which is what the stringer hangs against, is the deck surface minus the decking thickness. With 5/4 decking at 1 in actual, framing top is 45 in.
So the stringer’s top edge sits 1/2 in below the top of the rim joist. That gap is not an error, it is the difference between tread thickness and decking thickness:
Stringer top offset below the deck framing = tread thickness minus decking thickness.
| Tread material | Deck surface material | Stringer top sits |
|---|---|---|
| 2×6, 1.5 in | 5/4 decking, 1.0 in | 1/2 in below framing top |
| 2×6, 1.5 in | 2x decking, 1.5 in | Flush with framing top |
| 5/4, 1.0 in | 5/4 decking, 1.0 in | Flush with framing top |
| Composite, 1.0 in | Composite, 1.0 in | Flush with framing top |
| 2×6, 1.5 in | Composite, 1.0 in | 1/2 in below framing top |
Lay out total rise to the top of the framing instead of the top of the decking and the top riser comes out short by the decking thickness. That is where the phrase “cut the top riser short by the decking thickness” comes from, and it only makes sense once you see that the stringer meets framing while people walk on decking. We measure to the walking surface and let the offset fall out of the rule above.
Treads, stringer count and throat
Two 2×6 treads give 11 in of wood, and with a 1/4 in gap the tread is 11.25 in deep on an 11 in stringer run, so the nosing projects 1/4 in. Tread material governs stringer spacing, commonly around 16 in on center for 2x treads and tighter for thinner material, but your tread instructions and local code decide it.
Check the throat on the 2×12. Step hypotenuse = square root of 179.78 = 13.41 in. Material lost to the notch = 7.667 x 11 / 13.41 = 6.29 in. Throat = 11.25 minus 6.29 = 4.96 in, right at the roughly 5 in minimum many jurisdictions expect, so confirm locally. A 12 in run pushes the throat below that and you need wider stock.
The landing pad
Landing size at the bottom of an exterior stair is a code requirement in most places, commonly at least the stair width and around 36 in in the direction of travel, and the pad may need frost protection depending on local frost depth. Verify both with your building department. Slope the pad away so water does not pond at the stringer bottoms, and set stringer ends on a treated bearing plate or standoff hardware, not directly on wet concrete.
Cut one stringer, set it dry, and check top and bottom with a level and a tape before cutting the other two. Ten minutes, and it has saved us a 2×12 more than once.
Related guides
- Why 7-11 Is the Rule
- Stair Riser and Tread Count for an 8 ft Basement Drop
- Composite vs Wood: Board Length and Waste
- Crown Molding Linear Feet: Measuring With Miters
Sources and Further Reading
Run your own numbers with the Stair Calculator, or browse every tool on the calculators index. Coverage figures and material constants are cross-checked against manufacturer technical data sheets before publication. See our Methodology page for how figures are selected and verified.
Planning estimate only. Results assume standard conditions and are intended for material planning. Verify against your product’s technical data sheet and your local building code before purchasing. Structural, electrical, and gas work should be specified by a licensed professional.
Last updated: August 23, 2026
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