Working out 4 step stair stringer dimensions first — riser height, tread depth, total run — takes ten minutes with a framing square and saves a rebuild, because code allows only 3/8 inch of variation across a whole flight. The order: measure true rise, do the math, then cut.
4 Step Stair Stringer Dimensions
Stringers get cut from 2×12 stock, which measures 1-1/2 x 11-1/4 inches — plan notches from that size, not the nominal name.
Your site rarely matches either example. Finished flooring at the top landing and the bottom pad changes the first and last rises, so measure floor-to-floor height on site before trusting any chart.
| Stair Dimension | Limit Or Typical Value | Why It Matters |
|---|---|---|
| Riser height | 7-3/4 in. maximum | Taller risers turn a stair into a ladder. |
| Tread depth | 10 in. minimum | Shallow treads leave no room to land a foot. |
| Variation across a flight | 3/8 in. maximum | Uneven risers are the top cause of trips. |
| Nosing projection | 3/4 in. to 1-1/4 in. | Applies only where a tread projects past the riser. |
| Nosing radius | 9/16 in. maximum | Sharp edges catch shoes and bare feet. |
| Wood at the notch throat | 3.5 in. minimum | Thin throats split under load. |
| Stringer spacing | 36 in. maximum | Wider stairs need a third stringer. |
| 2×12 actual size | 1-1/2 x 11-1/4 in. | Cut notches from the real measurement. |
Laying Out A 4 Step Stringer On A 2×12
Set stair gauges on a framing square to the unit rise and unit run, trace that square down the edge of the 2×12, and cut each notch to the line.
- Clamp the 2×12, set the stair gauges — brass-bodied buttons clamping onto the square’s tongue and blade — at unit rise and unit run, walk the square down the board, and mark every tread and riser. Shorten the first riser by the thickness of finished flooring at the top.
- Cut on the waste side of each line with a circular saw, stopping short at every inside corner.
- Finish corners with a handsaw or jigsaw. Skipping this step lets overcuts weaken a stringer.
Fine Homebuilding’s stringer layout guide walks the same sequence with photos if the gauge settings give you trouble.
Then check the throat — wood left between the notch corner and the opposite edge. A correct stringer stands on the pad with its top notch flat against the rim and every tread edge level.
Where 4 Step Deck Stairs Go Wrong
Most failed deck stairs trace back to a measurement taken from the wrong surface, not a bad cut. The floor-to-floor rise drives every number, and it shifts the moment a pad gets poured or deck boards go down.
- Counting steps instead of measuring rise. A generic 4-step plan builds an out-of-code stair on a typical deck.
- Leaving flooring thickness out of the math. The top and bottom rises end up uneven.
- Overcutting notches. Cutting past the inside corner removes wood and weakens the stringer.
- Skipping the throat check. Less than 3.5 inches of wood behind the notch can fail inspection.
- Trusting a precut blank to fit. Verify a factory 4-step piece against your own rise and run first.
If a precut blank does match your numbers, our tested 4 step stringer picks cover the options worth hauling home. Either way the sequence stays the same: measure the true rise, divide by four, set the gauges, cut short of every corner, then check the throat before screwing anything down.
FAQs
Why Do The Top And Bottom Steps Come Out Uneven?
Finished flooring is usually the culprit. The top and bottom rises are measured from the surfaces people actually stand on, so a half inch of deck board or landing tile changes both. Work the finished thickness into the layout before cutting, then recheck the first and last rises against the middle ones — no more than 3/8 inch of difference is allowed.
How Many Stringers Do Four Deck Steps Need?
Anything wider usually needs a third stringer in the middle. Cut every stringer from the same layout, because the notches must match exactly or the treads will rock and the risers will sit out of line.
Can Deck Stair Stringers Be Cut From A 2×10?
A 2×10 measures roughly 1-1/2 x 9-1/4 inches, about two inches less depth than a 2×12. The published 3.5-inch throat minimum assumes a notched 2×12, so a shallower board leaves a thin margin once a 10-inch tread notch comes out of it. Most deck stairs are built from 2×12 stock for that reason.
References & Sources
- Fine Homebuilding. “Laying Out Basic Stair Stringers.” Walks the framing-square layout and notch-cutting sequence for a stringer.
- Home Depot. “Deck Stair Stringer Layout and Code Dimensions.” Source for the riser, tread, nosing, and throat dimensions cited in the table.