Stair Profile
Residential Stairs
Residential stairs are designed for daily use by all age groups, prioritizing comfort and safety. The Blondel formula (2h + b = 60-64 cm) ensures a natural stride rhythm. Maximum riser is typically 190 mm (7.75") and minimum tread is 250 mm (10").
Max Riser (h)
190 mm (7.75")
Min Tread (b)
250 mm (10")
Typical Angle
33° - 38°
Primary Use
Houses, Apartments, Villas
Blondel's Formula & Standard
2h + b = 600-640 mm
per IBC 2021 / R311.7
Stair Proportion Reference Table (Ergonomic Standards)
2h + b = 60-64 cm| Stair Type | Riser (h) | Tread (b) | Blondel Formula | Angle | Code |
|---|---|---|---|---|---|
| Residential (Private)Current | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / Residential |
| Commercial (Office) | 150 - 170 mm | 280 - 300 mm | 2h + b = 580-620 | 28° - 33° | IBC / OSHA |
| Public Assembly | 130 - 160 mm | 300 - 330 mm | 2h + b = 560-600 | 25° - 30° | IBC / ADA |
| Industrial / Factory | 170 - 200 mm | 250 - 280 mm | 2h + b = 600-660 | 33° - 40° | OSHA 1910.25 |
| Ship / Marine | 180 - 210 mm | 230 - 260 mm | 2h + b = 620-680 | 36° - 43° | IMO / SOLAS |
| Fire Escape | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / NFPA |
| Exterior / Landscape | 120 - 160 mm | 300 - 450 mm | 2h + b = 540-620 | 20° - 28° | Landscape Std |
| Spiral Stair | 170 - 195 mm | Variable (helical) | Tread width ≥ 220 | Variable | IBC / BS 5395 |
Stair Profile
Commercial Stairs
Commercial stairs serve higher traffic volumes and must accommodate a wider range of users including elderly and disabled persons. Lower risers and deeper treads reduce fatigue and improve safety during evacuation scenarios.
Max Riser (h)
170 mm (6.7")
Min Tread (b)
280 mm (11")
Typical Angle
28° - 33°
Primary Use
Offices, Malls, Hotels
Blondel's Formula & Standard
2h + b = 580-620 mm
per IBC 2021 / 1011.5
Stair Proportion Reference Table (Ergonomic Standards)
2h + b = 60-64 cm| Stair Type | Riser (h) | Tread (b) | Blondel Formula | Angle | Code |
|---|---|---|---|---|---|
| Residential (Private) | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / Residential |
| Commercial (Office)Current | 150 - 170 mm | 280 - 300 mm | 2h + b = 580-620 | 28° - 33° | IBC / OSHA |
| Public Assembly | 130 - 160 mm | 300 - 330 mm | 2h + b = 560-600 | 25° - 30° | IBC / ADA |
| Industrial / Factory | 170 - 200 mm | 250 - 280 mm | 2h + b = 600-660 | 33° - 40° | OSHA 1910.25 |
| Ship / Marine | 180 - 210 mm | 230 - 260 mm | 2h + b = 620-680 | 36° - 43° | IMO / SOLAS |
| Fire Escape | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / NFPA |
| Exterior / Landscape | 120 - 160 mm | 300 - 450 mm | 2h + b = 540-620 | 20° - 28° | Landscape Std |
| Spiral Stair | 170 - 195 mm | Variable (helical) | Tread width ≥ 220 | Variable | IBC / BS 5395 |
Stair Profile
Public Assembly Stairs
Assembly occupancies require the most comfortable stair proportions due to high pedestrian density and evacuation requirements. Riser heights are minimized and treads are maximized to prevent falls in crowded conditions.
Max Riser (h)
160 mm (6.3")
Min Tread (b)
300 mm (11.8")
Typical Angle
25° - 30°
Primary Use
Theaters, Stadiums, Museums
Blondel's Formula & Standard
2h + b = 560-600 mm
per IBC 2021 / ADA Standards
Stair Proportion Reference Table (Ergonomic Standards)
2h + b = 60-64 cm| Stair Type | Riser (h) | Tread (b) | Blondel Formula | Angle | Code |
|---|---|---|---|---|---|
| Residential (Private) | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / Residential |
| Commercial (Office) | 150 - 170 mm | 280 - 300 mm | 2h + b = 580-620 | 28° - 33° | IBC / OSHA |
| Public AssemblyCurrent | 130 - 160 mm | 300 - 330 mm | 2h + b = 560-600 | 25° - 30° | IBC / ADA |
| Industrial / Factory | 170 - 200 mm | 250 - 280 mm | 2h + b = 600-660 | 33° - 40° | OSHA 1910.25 |
| Ship / Marine | 180 - 210 mm | 230 - 260 mm | 2h + b = 620-680 | 36° - 43° | IMO / SOLAS |
| Fire Escape | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / NFPA |
| Exterior / Landscape | 120 - 160 mm | 300 - 450 mm | 2h + b = 540-620 | 20° - 28° | Landscape Std |
| Spiral Stair | 170 - 195 mm | Variable (helical) | Tread width ≥ 220 | Variable | IBC / BS 5395 |
Stair Profile
Industrial Stairs
Industrial stairs are designed for workers wearing safety boots and carrying materials. They allow steeper slopes than commercial stairs but require uniform riser heights and slip-resistant treads. Fixed ladders may substitute above certain heights.
Max Riser (h)
200 mm (7.9")
Min Tread (b)
250 mm (9.5")
Typical Angle
33° - 40°
Primary Use
Factories, Power Plants, Warehouses
Blondel's Formula & Standard
2h + b = 600-660 mm
per OSHA 1910.25 / EN ISO 14122
Stair Proportion Reference Table (Ergonomic Standards)
2h + b = 60-64 cm| Stair Type | Riser (h) | Tread (b) | Blondel Formula | Angle | Code |
|---|---|---|---|---|---|
| Residential (Private) | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / Residential |
| Commercial (Office) | 150 - 170 mm | 280 - 300 mm | 2h + b = 580-620 | 28° - 33° | IBC / OSHA |
| Public Assembly | 130 - 160 mm | 300 - 330 mm | 2h + b = 560-600 | 25° - 30° | IBC / ADA |
| Industrial / FactoryCurrent | 170 - 200 mm | 250 - 280 mm | 2h + b = 600-660 | 33° - 40° | OSHA 1910.25 |
| Ship / Marine | 180 - 210 mm | 230 - 260 mm | 2h + b = 620-680 | 36° - 43° | IMO / SOLAS |
| Fire Escape | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / NFPA |
| Exterior / Landscape | 120 - 160 mm | 300 - 450 mm | 2h + b = 540-620 | 20° - 28° | Landscape Std |
| Spiral Stair | 170 - 195 mm | Variable (helical) | Tread width ≥ 220 | Variable | IBC / BS 5395 |
Stair Profile
Ship / Marine Stairs
Marine stairs must accommodate vessel motion and limited space. They are typically steeper than land-based stairs with non-slip treads and handrails on both sides. Special consideration is given to evacuation routes under list conditions.
Max Riser (h)
210 mm (8.3")
Min Tread (b)
230 mm (9")
Typical Angle
36° - 43°
Primary Use
Ships, Offshore Platforms
Blondel's Formula & Standard
2h + b = 620-680 mm
per IMO / SOLAS Ch. II-2
Stair Proportion Reference Table (Ergonomic Standards)
2h + b = 60-64 cm| Stair Type | Riser (h) | Tread (b) | Blondel Formula | Angle | Code |
|---|---|---|---|---|---|
| Residential (Private) | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / Residential |
| Commercial (Office) | 150 - 170 mm | 280 - 300 mm | 2h + b = 580-620 | 28° - 33° | IBC / OSHA |
| Public Assembly | 130 - 160 mm | 300 - 330 mm | 2h + b = 560-600 | 25° - 30° | IBC / ADA |
| Industrial / Factory | 170 - 200 mm | 250 - 280 mm | 2h + b = 600-660 | 33° - 40° | OSHA 1910.25 |
| Ship / MarineCurrent | 180 - 210 mm | 230 - 260 mm | 2h + b = 620-680 | 36° - 43° | IMO / SOLAS |
| Fire Escape | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / NFPA |
| Exterior / Landscape | 120 - 160 mm | 300 - 450 mm | 2h + b = 540-620 | 20° - 28° | Landscape Std |
| Spiral Stair | 170 - 195 mm | Variable (helical) | Tread width ≥ 220 | Variable | IBC / BS 5395 |
Stair Profile
Fire Escape Stairs
Fire escape stairs are designed for rapid evacuation under stress conditions. They must meet strict dimensional uniformity requirements to prevent tripping. Enclosed fire stairs require fire-rated construction and pressurization.
Max Riser (h)
190 mm (7.5")
Min Tread (b)
250 mm (10")
Typical Angle
33° - 38°
Primary Use
Emergency exits, Fire stairs
Blondel's Formula & Standard
2h + b = 600-640 mm
per NFPA 101 / IBC 1009
Stair Proportion Reference Table (Ergonomic Standards)
2h + b = 60-64 cm| Stair Type | Riser (h) | Tread (b) | Blondel Formula | Angle | Code |
|---|---|---|---|---|---|
| Residential (Private) | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / Residential |
| Commercial (Office) | 150 - 170 mm | 280 - 300 mm | 2h + b = 580-620 | 28° - 33° | IBC / OSHA |
| Public Assembly | 130 - 160 mm | 300 - 330 mm | 2h + b = 560-600 | 25° - 30° | IBC / ADA |
| Industrial / Factory | 170 - 200 mm | 250 - 280 mm | 2h + b = 600-660 | 33° - 40° | OSHA 1910.25 |
| Ship / Marine | 180 - 210 mm | 230 - 260 mm | 2h + b = 620-680 | 36° - 43° | IMO / SOLAS |
| Fire EscapeCurrent | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / NFPA |
| Exterior / Landscape | 120 - 160 mm | 300 - 450 mm | 2h + b = 540-620 | 20° - 28° | Landscape Std |
| Spiral Stair | 170 - 195 mm | Variable (helical) | Tread width ≥ 220 | Variable | IBC / BS 5395 |
Stair Profile
Exterior / Landscape Stairs
Exterior stairs prioritize integration with landscape and accessibility. They often feature shallower slopes, wider treads, and durable materials (stone, concrete). Drainage and frost resistance are critical design considerations.
Max Riser (h)
160 mm (6.3")
Min Tread (b)
300 mm (12")
Typical Angle
20° - 28°
Primary Use
Gardens, Parks, Plazas
Blondel's Formula & Standard
2h + b = 540-620 mm
per Landscape Standards / BS 5760
Stair Proportion Reference Table (Ergonomic Standards)
2h + b = 60-64 cm| Stair Type | Riser (h) | Tread (b) | Blondel Formula | Angle | Code |
|---|---|---|---|---|---|
| Residential (Private) | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / Residential |
| Commercial (Office) | 150 - 170 mm | 280 - 300 mm | 2h + b = 580-620 | 28° - 33° | IBC / OSHA |
| Public Assembly | 130 - 160 mm | 300 - 330 mm | 2h + b = 560-600 | 25° - 30° | IBC / ADA |
| Industrial / Factory | 170 - 200 mm | 250 - 280 mm | 2h + b = 600-660 | 33° - 40° | OSHA 1910.25 |
| Ship / Marine | 180 - 210 mm | 230 - 260 mm | 2h + b = 620-680 | 36° - 43° | IMO / SOLAS |
| Fire Escape | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / NFPA |
| Exterior / LandscapeCurrent | 120 - 160 mm | 300 - 450 mm | 2h + b = 540-620 | 20° - 28° | Landscape Std |
| Spiral Stair | 170 - 195 mm | Variable (helical) | Tread width ≥ 220 | Variable | IBC / BS 5395 |
Stair Profile
Spiral Stairs
Spiral stairs save floor space but have variable tread widths and complex geometry. The walking line (at 2/3 radius) must satisfy tread depth requirements. They are permitted only in limited occupancy scenarios due to evacuation concerns.
Max Riser (h)
195 mm (7.7")
Min Tread (b)
220 mm (8.7") at walk line
Typical Angle
Variable (helical)
Primary Use
Lofts, Towers, Space-saving
Blondel's Formula & Standard
Tread width ≥ 220 mm
per IBC 1009.9 / BS 5395-2
Stair Proportion Reference Table (Ergonomic Standards)
2h + b = 60-64 cm| Stair Type | Riser (h) | Tread (b) | Blondel Formula | Angle | Code |
|---|---|---|---|---|---|
| Residential (Private) | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / Residential |
| Commercial (Office) | 150 - 170 mm | 280 - 300 mm | 2h + b = 580-620 | 28° - 33° | IBC / OSHA |
| Public Assembly | 130 - 160 mm | 300 - 330 mm | 2h + b = 560-600 | 25° - 30° | IBC / ADA |
| Industrial / Factory | 170 - 200 mm | 250 - 280 mm | 2h + b = 600-660 | 33° - 40° | OSHA 1910.25 |
| Ship / Marine | 180 - 210 mm | 230 - 260 mm | 2h + b = 620-680 | 36° - 43° | IMO / SOLAS |
| Fire Escape | 170 - 190 mm | 250 - 280 mm | 2h + b = 600-640 | 33° - 38° | IBC / NFPA |
| Exterior / Landscape | 120 - 160 mm | 300 - 450 mm | 2h + b = 540-620 | 20° - 28° | Landscape Std |
| Spiral StairCurrent | 170 - 195 mm | Variable (helical) | Tread width ≥ 220 | Variable | IBC / BS 5395 |