Door Rough Openings vs. Stair Building Code Dimensions
Comparing 2 standards across 15 specifications. 15 key differences identified.
Door rough openings are standardized framing openings in wood and steel stud walls engineered to accept pre-hung door frames, shims, and finished jambs. Under standard architectural guidelines, rough opening width is calculated as Nominal Door Width + 2.0 inches, and rough opening height is calculated as Nominal Door Height + 2.5 inches, with standard 36×80" doors accommodating ADA accessibility.
Residential stair construction is strictly regulated under the International Residential Code (IRC Section R311.7) and OSHA into mandatory geometric limits: maximum 7-3/4 inch (197 mm) riser height, minimum 10 inch (254 mm) tread run depth, 36 inch minimum width, 6'8" headroom, and 34–38 inch handrail height.
Specification Comparison Table
15 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Standards
|
WDMA I.S. 1-A / ANSI A250.8 / ADA Standards Section 404 | IRC Section R311.7 (Residential) / IBC Section 1011 (Commercial) / OSHA 1910.25 |
|
Rough Opening Width Formula
|
Nominal Door Width + 2.0 inches (51 mm) | — |
|
Rough Opening Height Formula
|
Nominal Door Height + 2.5 inches (64 mm) | — |
|
30×80" Bedroom Door (2/6 × 6/8)
|
Rough Opening: 32.0 × 82.5 inches (813 × 2096 mm) | — |
|
32×80" Standard Entry (2/8 × 6/8)
|
Rough Opening: 34.0 × 82.5 inches (864 × 2096 mm) | — |
|
36×80" ADA Entry (3/0 × 6/8)
|
Rough Opening: 38.0 × 82.5 inches (965 × 2096 mm) | — |
|
Standard 2×4 Wall Jamb Depth
|
4-9/16 inches (116 mm) = 3.5" stud + two 1/2" drywall layers | — |
|
Standard 2×6 Wall Jamb Depth
|
6-9/16 inches (167 mm) = 5.5" stud + two 1/2" drywall layers | — |
|
Maximum Riser Height
|
— | 7-3/4 inches (197 mm) IRC Residential | 7.0 inches (178 mm) IBC Commercial |
|
Minimum Riser Height
|
— | 4.0 inches (102 mm) | Prevents tripping from unexpectedly shallow steps |
|
Minimum Tread Run Depth
|
— | 10.0 inches (254 mm) IRC with nosing | 11.0 inches (279 mm) IBC Commercial |
|
Maximum Riser / Tread Tolerance
|
— | Maximum 3/8 inch (9.5 mm) variance between the tallest and shortest riser in a single flight |
|
Minimum Stairway Clear Width
|
— | 36 inches (914 mm) clear width above handrail height (IRC R311.7.1) |
|
Minimum Vertical Headroom
|
— | 6 feet 8 inches (2032 mm / 80 in) measured vertically from the sloped tread nosing line |
|
Handrail Height Standard
|
— | 34 to 38 inches (864 to 965 mm) measured vertically from the leading edge of stair treads |