⚠️ The High-Traffic Hazard: The Stakes for Common Stairs
The statistics on stair-related injuries are alarming, but when we move from a single private dwelling to a Common Stair (serving blocks of flats or multi-user buildings), the stakes are immediately higher.
In the UK, thousands of serious falls occur annually, and in a shared building, the design must accommodate everyone: the young, the elderly, and those carrying heavy loads or mobility aids. Any flaw in geometry here is a danger multiplied by every resident and visitor.
As a design professional, my mandate is safety and strict adherence to code. This requires a level of precision that demands a powerful 3D BIM workflow.
🇬🇧 Zero Tolerance for Error: UK Common Stair Regulations
In the UK, the design of a Common Stair is governed by Approved Document K (Protection from falling, collision and impact), falling under the General Access Stair category. These standards are intentionally stricter than those for a Private Stair:
| Dimension | UK Regs (General Access/Common Stair) | Why it Matters |
| Maximum Pitch | 38º | Significantly shallower than a private stair (42º) to improve usability for all ages and mobility levels. |
| Maximum Rise (R) | 170mm | Lower rise height is crucial for easy ascent by the elderly or those with limited knee flexibility. |
| Minimum Going (G) | 250mm | Deeper tread is required to provide more stable footing and reduce the risk of overstepping or tripping. |
| Critical Formula | 550mm < 2R + G < 700 mm | This core relationship must be met with the tighter R and G constraints, making accurate calculation essential. |
| Headroom | Minimum 2000mm | Mandatory clearance to prevent users from striking their head. |
| Guarding | 1100mm Minimum Height on Landings | Higher barrier for increased protection in public areas (often 900mm on the flights). |
The challenge is fitting these tighter, safer dimensions into a realistic floor plan. A simple error of 5mm the rise on a Common Stair is a code violation and a guaranteed trip hazard for daily users.
💡 The Solution: My 30 Years of Vectorworks Expertise
For three decades, my use of the Vectorworks BIM (Building Information Modeling) workflow has been the definitive tool for resolving these high-stakes design conflicts with absolute precision. This is what I teach:
1. Instant Code Enforcement (Beyond Manual Check)
When training designers on Common Stair construction, we embed understanding on the Building Regulations you are working with, for example, the precise 170mm max rise and 250mm min going and ensure we put this directly into the Vectorworks Stair Tool. This is not a manual check—it’s an enforced compliance tool that:
Allows the designer to quickly iterate through design options (riser/going combinations).
Flags a critical error immediately if the design exceeds the 38º pitch limit or violates the 2R + G formula. This proactive approach eliminates the most common sources of code failure.
2. Verification of Complex Geometry in 3D
For any stair that deviates from a straight run—especially those with winders—the difficulty increases exponentially.
In Vectorworks, we use the 3D model to confirm that the minimum 250mm going is maintained along the critical walking line for every single tapered tread. This geometric assurance is vital when designing for multi-user buildings.
3. Headroom and Double Handrail Assurance
Common Stairs often interface with complex structural elements. The 3D model is essential for:
Headroom Clearance: Conducting virtual walkthroughs to verify that the 2000mm minimum headroom is maintained across the entire flight, especially at structural overlaps.
Handrail Placement: Visually and dimensionally confirming that for stairs over 1 metre wide, handrails are correctly placed on both sides at the required heights (e.g., 900mm on the pitch line, 1100mm on landings), as mandated for General Access Stairs.
The take-away is clear: For safety-critical, high-traffic elements like a Common Stair, your design tool must do more than draw lines—it must engineer compliance. My 30 years of Vectorworks expertise ensures that you not only meet the legal minimums but deliver a stair that is safe and predictable for every user.
Are you designing common access routes in the UK? Let's discuss how BIM can guarantee your stair compliance. Follow me for more professional insights into technical architecture.
Join my community to access my 30 years experience: https://www.skool.com/vectorworks-training/about
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