Stair Calculator UK - Building Regulations Compliant
Design safe, comfortable domestic staircases compliant with Approved Document K
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UK Building Regulations for Stairs (Part K)
All domestic staircases in England and Wales must comply with Approved Document K: Protection from falling, collision and impact. These regulations ensure stairs are safe and comfortable to use.
| Requirement | Private Stairs (Domestic) | Common/Utility Stairs |
|---|---|---|
| Maximum Rise | 220mm | 190mm |
| Minimum Going | 220mm | 250mm |
| Maximum Pitch | 42° | 38° |
| Minimum Width | 800mm (recommended 850mm+) | 900mm (1000mm for fire escape) |
| Minimum Headroom | 2000mm (1900mm in loft conversions) | 2000mm |
| Handrail Height | 900-1000mm above pitch line | 900-1000mm above pitch line |
| Maximum Steps per Flight | 16 (with landings) | 16 (with landings) |
Essential Stair Design Formulas
Stair Terminology Diagram
Key stair components: Rise (vertical height of step), Going (horizontal depth of tread), Pitch Line (angle of stair), Nosing (projecting edge of tread)
7 Essential Stair Building Tips
1. Measure Twice, Cut Once
Always measure the total rise (floor to floor) at multiple points. Floors are rarely perfectly level, so take the measurement at the actual stair location.
2. Consistency is Critical
All risers must be the same height (within 3mm tolerance). Inconsistent rises cause trips and fails Building Control inspection.
3. Check the 2R+G Formula
Before finalising, verify 2R+G equals 550-700mm. This centuries-old formula ensures comfortable walking rhythm on your stairs.
4. Plan for Floor Finishes
Account for floor covering thickness (carpet, tiles, laminate) when calculating total rise. The finished floor-to-floor height determines your riser count.
5. Consider Furniture Access
Standard 850mm width allows most furniture through. For larger items, consider 900mm+ width or ensure access through windows/loft hatches.
6. Install Handrails Correctly
Handrails must be 900-1000mm above pitch line, graspable (32-50mm diameter), and extend 300mm beyond top and bottom steps.
7. Get Building Control Sign-Off
Staircases require Building Control approval. Submit plans before construction and arrange inspection before covering with plasterboard.
7 Common Stair Building Mistakes
1. Ignoring Floor Finish Heights
Failing to account for carpet or tiles causes the first/last step to be different heights, creating a trip hazard and failing inspection.
2. Insufficient Headroom
Not checking headroom throughout the flight. The 2000mm minimum applies at all points along the pitch line, not just at landings.
3. Too Steep a Pitch
Exceeding 42° pitch to save space. Steep stairs are dangerous and uncomfortable. Redesign the layout if space is tight.
4. Inadequate Stringer Support
Stringers must be properly fixed at top and bottom. Loose stringers cause squeaking, movement, and structural issues.
5. Wrong Baluster Spacing
Balusters must be spaced so a 100mm sphere cannot pass through (to prevent child head entrapment). This is a strict Building Regs requirement.
6. Forgetting Winder Rules
Winder treads must have 50mm minimum at narrow end and the going measurement taken at centre. Many DIYers get this wrong.
7. No Building Notice/Application
Installing stairs without Building Control notification. This causes problems when selling and may need to be ripped out and rebuilt.
Stair Width Guidelines
| Width | Suitability | Handrail Requirement |
|---|---|---|
| 800mm | Absolute minimum for domestic. Tight for furniture, difficult to pass another person. | One side minimum |
| 850mm | Standard domestic width. Acceptable for most homes, allows small furniture through. | One side minimum |
| 900mm | Comfortable width. Easier furniture access, two people can just pass. | One side minimum |
| 1000mm | Spacious domestic stair. Good furniture access, comfortable passing. | One side minimum |
| 1000mm+ | Wide staircase. Excellent access, may suit period or larger properties. | Both sides required |
Official UK Stair Building Resources
Approved Document K
The official Building Regulations document covering stairs, ramps, guards and protection from falling.
GOV.UK - Document K →LABC (Local Authority Building Control)
Guidance on Building Regulations compliance for domestic staircases from local authority building control.
LABC Guidance →TRADA (Timber Research)
Technical guidance on timber staircase design, construction methods and structural requirements.
TRADA Technical →Planning Portal
Government guidance on when stairs need Building Regulations approval and the application process.
Planning Portal →HSE (Health & Safety Executive)
Workplace stair safety requirements and guidance on preventing falls on stairs during construction.
HSE Guidance →CITB (Construction Industry Training)
Training courses and qualifications for staircase joinery and carpentry in the UK.
CITB Training →Frequently Asked Questions
For private domestic stairs in the UK, Building Regulations Approved Document K allows a maximum pitch of 42 degrees. The ideal pitch range is between 30-38 degrees for comfortable use. Steeper stairs are harder to climb and more dangerous to descend, which is why regulations impose this limit. Utility stairs and common stairs in flats have a stricter maximum of 38 degrees.
The 2R+G formula (twice the rise plus the going) is a comfort equation used to design ergonomic stairs that match natural walking rhythm. For a comfortable stair, 2R+G should equal between 550mm and 700mm, with 620mm being ideal. For example, with a 180mm rise and 250mm going: (2 × 180) + 250 = 610mm, which is within the comfortable range. This formula has been used for centuries and is referenced in British Standards.
For private domestic stairs in the UK, Building Regulations Part K specifies a maximum rise of 220mm per step. There is no strict minimum, but rises below 150mm feel too shallow and are uncommon. The ideal rise is between 170mm and 190mm for comfortable climbing. For common stairs (in blocks of flats) the maximum is 190mm, and for buildings other than dwellings, it's 170mm.
Building Regulations Approved Document K requires a minimum going of 220mm for private domestic stairs. The going is measured horizontally from the nosing of one tread to the nosing of the next. Deeper goings (250-270mm) are more comfortable but require more floor space. For common stairs the minimum is 250mm, and for buildings other than dwellings it's 280mm.
Building Regulations require a minimum headroom of 2000mm (2 metres) measured vertically from the pitch line to any obstruction above. This applies throughout the entire flight, not just at landings. In loft conversions where space is genuinely limited, a reduced headroom of 1.9m may be acceptable at the centre of the stair, reducing to 1.8m at the sides, but this requires Building Control agreement.
Building Regulations require at least one handrail on any flight of stairs with two or more risers. Stairs over 1000mm wide require handrails on both sides. Handrails must be between 900mm and 1000mm above the pitch line, graspable (32-50mm diameter), and extend 300mm beyond the top and bottom of the flight. They must also be continuous - no gaps at newel posts.
Stringer length is calculated using Pythagoras theorem: √(total rise² + total run²). For example, with a 2600mm total rise and 3500mm total run: √(2600² + 3500²) = √(6,760,000 + 12,250,000) = √19,010,000 = 4361mm. Add 200-300mm at each end for fixing to the trimmer and floor, so you'd need stringers approximately 4800-4900mm long. Always buy timber slightly longer than calculated.
Winder stairs use triangular (tapered) treads instead of a landing to change direction, typically turning 90 or 180 degrees. They save significant space compared to quarter or half landings - often 600mm or more. Building Regulations require winder treads to have a minimum going of 50mm at the narrow end and the standard going (220mm minimum) measured at the centre of the tread. Three treads turning 90° is typical; avoid more than six treads in a turn.
Related Construction Calculators
About This Stair Calculator
This UK Stair Calculator has been developed to help homeowners, builders, and DIY enthusiasts design safe, comfortable staircases that comply with Building Regulations Approved Document K. The calculator uses industry-standard formulas including the 2R+G comfort equation to ensure your staircase meets both legal requirements and ergonomic best practices.
Our calculations are based on the current Building Regulations for England and Wales. Scotland has similar requirements under Technical Handbook Section 4, and Northern Ireland under Technical Booklet H. While the principles are the same, always check local requirements for your specific location.
This calculator is designed for private domestic staircases. Common stairs in blocks of flats, and stairs in commercial or public buildings, have stricter requirements and should be designed by a qualified professional.
Important: While this calculator provides accurate results based on the information entered, you must obtain Building Control approval for any new staircase installation. Building Control will inspect the stair before it's enclosed with plasterboard.
Pro Tips for Accurate Results
- Double-check your input values before calculating
- Use the correct unit format (metric or imperial)
- For complex calculations, break them into smaller steps
- Bookmark this page for quick future access
Understanding Your Results
Our Stair Calculator provides:
- Instant calculations - Results appear immediately
- Accurate formulas - Based on official UK standards
- Clear explanations - Understand how results are derived
- 2025/26 updated - Using current rates and regulations
Common Questions
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Yes, all our calculators are 100% free to use with no registration required.
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Our calculators use verified formulas and are regularly updated for accuracy.
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