Stringer stock
2x10 vs 2x12 Stair Stringer: Throat Depth and Strength
2x10 vs 2x12 for stair stringers: how throat depth after notching affects strength, when a 2x10 is enough, and why most stairs use 2x12 stringer stock.
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Throat depth after notching: 2x10 vs 2x12
The same tread notch leaves a deeper, stronger throat on a 2x12 than on a 2x10, which is why the larger stock is the notched-stringer default.
Throat Depth Is The Number That Matters
When you notch a stringer for treads and risers, what remains behind the deepest notch is the throat. The throat carries the load, so its depth, not the nominal board size, determines stringer strength. A 2x12 starts with more material, so after the same notch it keeps a deeper throat than a 2x10. That is the core of the comparison.
How Notching Eats Into The Board
A typical residential stair with a 7 inch rise and a 10 to 11 inch run cuts a notch roughly that size into the stringer. On a 2x10 (about 9.25 inches actual), that notch can leave a worryingly thin throat. On a 2x12 (about 11.25 inches actual), the same notch leaves more material behind it, which is why the 2x12 is the default for most cut stringers.
The Minimum Throat Rule Of Thumb
Many builders aim for a minimum throat of around 3.5 to 5 inches behind the notch, with some codes and references citing specific minimums. The exact figure depends on span, support, and local code, but the principle is constant: a shallow throat is a weak stringer, and a weak stringer is a safety problem on every step.
When A 2x10 Is Genuinely Enough
A 2x10 can work for short, low-rise, well-supported stairs, especially with a shallower rise that cuts a smaller notch, or for cleated stringers that are not notched at all. If the run is short and the stringer is well supported top and bottom, a 2x10 may keep an adequate throat. Run the numbers rather than assuming.
Cleated Stringers Change The Math
A cleated or housed stringer carries treads on cleats or in routed housings instead of open notches, so it keeps the full board depth as throat. With that approach, a 2x10 or even narrower stock can be plenty because nothing is notched away. The 2x10 vs 2x12 question mainly applies to open, notched (sawtooth) stringers.
Check The Throat Before You Cut
The reliable move is to calculate the throat depth for your exact rise, run, and stock before cutting. A stringer calculator shows the throat that a given board and notch will leave, so you can confirm a 2x10 is safe or step up to a 2x12 before wasting a board. It turns a guess into a number.
Cost, Weight, And Availability
A 2x12 costs more, weighs more, and is sometimes harder to find clear and straight than a 2x10. Those are real considerations, but they should never override throat depth. The right order is: confirm the throat your stair needs, then choose the smallest stock that safely provides it, which for most notched stairs is a 2x12.
Compare
2x10 vs 2x12 stringer stock
| Factor | 2x10 | 2x12 | Edge |
|---|---|---|---|
| Throat after notch | Thin on standard rise | Deeper, stronger | 2x12 |
| Best for | Short, low-rise, supported | Most notched stairs | Depends |
| Cost & weight | Lower | Higher | 2x10 |
| Cleated option | Full depth kept | Full depth kept | Tie |
Field Checklist
- Judge stringers by throat depth, not nominal size.
- Default to 2x12 for notched (sawtooth) stringers.
- Calculate the throat your rise and run will leave.
- Consider a 2x10 only for short, low-rise, supported stairs.
- Use cleated stringers to keep full board depth.
FAQ
Common questions
Can I use a 2x10 for stair stringers?
Sometimes, for short, low-rise, well-supported stairs or cleated stringers. On a standard notched stair, a 2x10 can leave too thin a throat, so most builders use a 2x12.
What is throat depth on a stringer?
It is the material left behind the deepest tread notch. The throat carries the load, so its depth determines the stringer's strength.
Why is 2x12 the standard for stringers?
After cutting a standard tread notch, a 2x12 keeps a deeper throat than a 2x10, giving the stringer enough remaining material to be strong.
What is the minimum throat depth?
Builders commonly target around 3.5 to 5 inches, but the exact minimum depends on span, support, and local code. Verify against your code.
Do cleated stringers need a 2x12?
Not necessarily. Cleated or housed stringers are not notched, so they keep full board depth and can use smaller stock.
How do I know if my throat is too thin?
Calculate the throat for your rise, run, and stock before cutting. A stringer calculator shows the remaining throat so you can confirm it is adequate.
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