Recommendations Regarding Fire Safety on Balconies in High-Rise Residential Blocks

Fire Safety on Balconies in High-Rise Residential Buildings

Following significant regulatory changes after the Grenfell tragedy, balcony design in high-rise residential buildings has come under increased scrutiny. Balconies are now explicitly considered part of the external wall system under Approved Document B (ADB), meaning stricter controls apply to combustibility and fire performance.

This whitepaper summarises the current regulatory landscape, practical fire test findings, and engineering solutions to improve fire safety in balcony systems.

Executive Summary

• Balconies are now treated as part of the external façade under ADB.
• Buildings over 18m or within 1m of a boundary require non-combustible materials (typically A2-s1,d0 or A1).
• Decking selection plays a critical role in limiting fire spread.
• Aluminium soffits significantly reduce oxygen flow and upward fire spread.
• Cavity barriers at balcony connections must maintain integrity and insulation for up to 120 minutes.
• The status of laminated toughened glass in balustrades remains under regulatory review.

Balconies Under Approved Document B

Under current regulations, balconies are classified as specified attachments forming part of the external wall. This means:

• Balconies above 18m must be constructed from non-combustible materials.
• Balconies within 1m of a relevant boundary must also meet non-combustibility requirements.
• Decking must typically achieve A2 classification where required.

Balconies rarely form part of an escape route, but designers must consider extended travel distances and potential classification as an “inner room” under means of escape guidance.

Decking Performance in Fire

Decking material selection significantly affects fire behaviour. Testing and case studies demonstrate:

• Class C and timber decking can burn through quickly, allowing debris to fall.
• Class B materials resist ignition longer but can still fail under sustained heat.
• Class A and A2 aluminium decking remains non-combustible and maintains structural integrity.

Where balconies are above 18m or near boundaries, non-combustible decking is mandatory. Even in lower-rise buildings, risk assessments increasingly favour A2-rated solutions.

The Protective Effect of Aluminium Soffits

Fire testing has demonstrated that solid aluminium soffits provide significant protection by:

• Limiting oxygen supply to a balcony fire.
• Preventing burning debris from falling.
• Reflecting and deflecting heat away from balconies above.
• Reducing vertical fire spread.

Where soffits are omitted or heavily perforated, the risk of rapid vertical fire spread increases substantially.

Cavity Barriers & Balcony Connections

Approved Document B requires cavity barriers within external wall cavities to maintain compartmentation. These barriers must provide:

• Integrity — preventing flame passage.
• Insulation — limiting temperature rise on the unexposed face.

Balcony cantilever connections create a complex interface between structure, waterproofing, thermal breaks and fire stopping. Tested solutions capable of achieving up to 120 minutes of fire resistance are essential, particularly in high-rise buildings.

Laminated Toughened Glass in Balustrades

The use of laminated toughened glass in balcony balustrades has been subject to industry debate following amendments to Regulation 7.

While glass is generally considered Class A1 under European classification, exemptions clearly apply to window glazing but are less explicit for balcony guardings.

Industry bodies and the BS 8579 committee have called for clarification. Current evidence does not demonstrate that laminated glass balustrades materially increase fire spread risk in buildings otherwise constructed from non-combustible materials.

General Conclusions

Balcony fire safety requires a holistic approach combining:

• Non-combustible primary materials
• A2-rated decking where required
• Effective aluminium soffits
• Properly tested cavity barrier solutions
• Clear understanding of laminated glass compliance

Building owners and designers must apply professional judgement and seek fire engineering advice where ambiguity exists.