Five Key Considerations for Designing High-Rise Decking

Designing terraces and balconies for high-rise buildings requires more than just strong aesthetics. Topics like fire safety, accessibility, slip resistance and long-term durability must all be considered from the outset to create compliant and functional outdoor spaces.

Here are five key considerations when designing decked terrace and balcony areas for high-rise buildings.

1. Fire Safety Regulations

For residential buildings over 11 metres in height, Approved Document B requires external wall systems and specified attachments, including balconies, to use non-combustible materials.

Decking systems should therefore achieve a Class A fire rating across all components, not just the visible finish. Fully non-combustible systems such as Zerodeck simplify compliance.

For roof terraces, the classification to consider is BROOF(t4), awarded to a fully tested system from roof membrane through to the finish. If any component is substituted, the build-up must be retested as a complete system to retain its rating.

2.  Accessible Design 

High-rise terraces should be designed to be inclusive and step-free, allowing access for all users. This was one of the key components for the Google HQ where wheelchair ramps were required for access on to the roof terrace.

Because roofs are often laid to fall for drainage, achieving level thresholds or compliant ramp gradients typically requires a pedestal system capable of precise height and slope adjustment. Millimetre-accurate correction helps maintain accessibility without compromising drainage.

3. Safety Matters

External flooring can become slippery in wet conditions, particularly on exposed balconies and terraces.

Slip resistant performance should be assessed using the Pendulum Test Value (PTV). The Health and Safety Executive recommends a minimum wet PTV of 36 for outdoor areas exposed to wet conditions. Ramps and high-traffic routes often benefit from higher PTV values to provide greater confidence underfoot.

4. Material Selection

High-rise environments expose materials to wind loads and UV radiation. Wind uplift is typically not an issue for decking systems as the components are locked together, ensuring that elements won’t lift even in the strongest winds.

Suitable decking should be specified to maintain colour stability and withstand long-term weathering.
 

5. Green Spaces

Urban planning policies increasingly require the integration of green infrastructure, particularly in city environments.

Roof terraces provide an opportunity to contribute toward targets through planting, trees and biodiverse elements. Early coordination between decking, planting zones and structural load capacity is essential to ensure performance and compliance.

Projects such as Cannon Street, where mature roof planting now forms part of the project’s identity, demonstrate how decking systems can work in tandem with green infrastructure to deliver long-term performance.

Designing high-rise decking is ultimately about balancing regulation, usability and longevity. Systems such as Class A fire-rated Zerodeck or sustainable Silvadec offer strong slip resistance alongside durability and low maintenance requirements.

If you’re working on a high-rise project, our team can help you specify a decking system that meets regulatory requirements while supporting long-term performance.