The 7.5m Rule: How Building Height Triggers Stricter Fire Regulations

If you’re planning a new build, loft conversion, roof terrace or extension, the height of your building isn’t just about design—it has a major impact on fire safety regulations. Once a residential building exceeds 7.5m in height, it triggers stricter Building Control requirements that can significantly affect materials, design choices, and costs.

Here’s what you need to know before your project gets caught out.

Why 7.5m Matters in Fire Safety Regulations

In December 2022, Approved Document B (Fire Safety) was updated, setting 7.5m as the critical threshold for residential buildings. If the distance between the ground floor level and the floor level of the highest habitable room (which includes roof terraces) exceeds this height, it must comply with additional fire protection measures, which means uprating the smoke detection and implementing fire supression (sprinklers etc). This applies to single dwellings, flats, and multi-occupancy buildings, so whether you’re extending upwards or building from scratch, you need to be aware of the rules.

Key Fire Safety Regulations That Apply Over 7.5m

1. Smoke detection to be upgraded

🔹 Each habitable room should have an interconnected, mains powered smoke alarm.

Impact: Before, smoke alarm and heat detectors were only needed at each landing plus the kitchen. Under these new regulations, we have seen 20+ smoke alarms going into a property to satisfy this regulation.

2. Sprinkler Systems Required in projects Over 7.5m

🔹 For all buildings (even single dwellings), once you exceed 7.5m, automatic fire suppression systems (sprinklers) are mandatory.

Impact: If you’re project is above this threshold, sprinklers must be included in the design, adding cost and complexity.

How to Avoid Issues with Building Control

✔ Measure from the correct datum point – Building height is taken from ground level to the highest occupied floor. Be precise to avoid hitting the threshold unintentionally.

✔ Plan for a protected stairway early – If you’re converting a loft or adding storeys, work fire safety into your staircase design before submitting plans.

✔ Consult with Building Control early – If your project is close to 7.5m, get pre-application advice to avoid costly surprises during construction.

The Verdict: Should You Stay Under 7.5m?

🔹 If you can stay under 7.5m, you avoid stricter fire regulations, which can save money and simplify approvals.

🔹 If your design must go over 7.5m, budget for fire safety upgrades—especially protected staircases, smoke detection, and potential sprinkler systems.

At Bloom Builders, we navigate fire regulations and Building Control on high-end residential projects every day. If your build is borderline 7.5m, we can advise on the best approach to stay compliant while keeping costs under control.

📞 Get in touch to discuss your project.