ADA compliant stairs need uniform risers between 4″ and 7″ high, treads at least 11″ deep, no open risers, a nosing radius of ½” max and a nosing projection of 1½” max. These rules are in Section 504 of the 2010 ADA Standards. Below is a summary of the rules, and then how to model the stair in Advance Steel with my free template.
Code note: this post quotes the 2010 ADA Standards (Section 504) and IBC 2021 Chapter 10, from the public texts. Your job may be under a different code edition or a local code, like Chicago’s. The architect sets which rules apply, and the engineer of record checks the steel. Always check before you detail a real stair.
What are the ADA stair requirements?
From the 2010 ADA Standards, Section 504:
| Item | ADA rule | Section |
|---|---|---|
| Risers | Uniform. 4″ min, 7″ max | 504.2 |
| Treads | Uniform. 11″ deep min | 504.2 |
| Open risers | Not permitted | 504.3 |
| Tread surface | Firm, stable, slip resistant (Section 302). Slope 1:48 max | 504.4 |
| Nosing radius | ½” max at the leading edge | 504.5 |
| Nosing projection | 1½” max over the tread below | 504.5 |
| Nosing underside | Curved or beveled, or the riser sloped under the tread, 30° max from vertical | 504.5 |
| Handrails | Both sides, per Section 505 | 504.6, 505.2 |
| Wet conditions | Treads and landings must not collect water | 504.7 |
Handrails have their own rules in ADA 505: 34″–38″ high (505.4), 1½” clear from the wall (505.5), and continuous along each flight (505.3). In this post I only cover the stair itself. See handrails in Advance Steel for the rails.
Which stairs have to be ADA compliant?
ADA 210.1 says interior and exterior stairs that are part of a means of egress must meet Section 504. The exceptions are:
- Stairs outside public use areas in detention and correctional facilities.
- In alterations, stairs between levels that are already connected by an accessible route. These still need ADA 505 handrails when the stairs are altered.
- Aisle stairs in assembly areas.
- Stairs that connect play components.
The ADA applies to public accommodations, commercial facilities, and state and local government buildings. Private homes are covered by the residential building code instead.
How is the building code different?
Most jobs also have to meet the building code. IBC 2021 is stricter in two places:
- Nosing projection: IBC 1011.5.5.1 allows only 1¼”, not 1½”.
- Nosing radius: IBC 1011.5.5 requires a curvature or bevel between 1/16″ and 9/16″.
Stair width isn’t in ADA 504. IBC 1011.2 sets it at 44″ (36″ for an occupant load under 50). If the stair is part of an accessible means of egress, IBC 1009.3.2 wants 48″ clear between handrails, unless the building is fully sprinklered.
So use the smaller numbers when both apply. My example below uses 36″ between handrails; check the width your job needs.
Does a nosing save space on the stair?
Not in the run. Under IBC 1011.5.2, tread depth is measured between the front edges (nosings) of the treads. So 8 treads still take 8 × 11″ = 88″ of run, nosing or not. What the nosing does is make each tread plate deeper than the run, so the step feels bigger to walk on.
How do I make ADA stairs in Advance Steel?
Download the template
Get my template here (zip). I made it in Advance Steel 2022, so newer versions will upgrade the file when you open it.
Watch the video
Step 1: lay out the step
Draw rectangles in plan for:
- the 1½” stringer,
- 1½” handrail clearance,
- the 1¼” handrail,
- 36″ clear between handrails.
Then draw a line for the riser height on the inside of the stringer. In this example, 7″.
Step 2: copy the step
Group the rectangles and copy them for each step, offset by the run.
Step 3: place the stair
- Go to Home > Extended Modeling > Straight Stair.
- Type 0 and press Enter (start and end points).
- Pick the bottom point, then the top point.
- For alignment, pick 2 (right). The stair is created and the dialog opens.
Step 4: load the template
In Properties > Library, pick ADA Compliant Stairs:
Step 5: set the width
Before you close the dialog, set the width: 36″ between handrails + 1½” clearance + 1¼” handrail on each side = 41½”.
Close the dialog.
How do I trim the stringers?
Use the UCS tools in the Advance Steel Tool Palette (Home tab):
- Move the UCS to where you want to cut and rotate it so the XY plane is the cut plane.
- Tool Palette > Features > Shorten at UCS. Select both stringers and press Enter.
Bottom of the stringers
Same steps, with the UCS set so the stringers sit flat on the floor:
First riser
- Rotate the UCS so it’s parallel to the face of the stringer.
- Switch to 2D Wireframe so it’s easier to pick points.
- Tool Palette > Features > Rectangular contour, 2 points and cut off the extra material.
- To remove the support angles at the bottom, rotate the UCS square to the stringer and use Rectangular contour, 2 points again.
Top of the stair
Do the same at the top. First a vertical cut on the stringers:
Then a horizontal cut:
Trim the top step with Rectangular contour, 2 points:
Then remove the support angles with the same tool. The stair is done:
How do I change the nosing or tread size?
Double-click the gray box around the stair to open its dialog:
Go to Step – General > Tread Dimensions:
Why can’t I move the stair?
In Advance Steel 2022 you often can’t move a stair in a shaded visual style. Switch to 2D Wireframe and use Move. That works.
On a complex model, you can also build the stair off to the side and move it into place when you’re happy with it.
What mistakes should I avoid?
- Measuring the tread from the riser. Tread depth is nosing to nosing.
- Using the ADA 1½” nosing on an IBC job. IBC allows 1¼”.
- Sharp nosings. ADA allows a ½” radius max; IBC wants a 1/16″ to 9/16″ curve or bevel.
- Open risers. Not allowed under ADA 504.3.
- Assuming 36″ is wide enough. Check IBC 1011.2 and 1009.3.2.
If you’re looking at hardware or software upgrades, my toolbox page lists the tools I use and any discounts I know of.
