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BS 8579:2020 - Balcony Design Standard & Decking Solutions

Timothy Gore

Published on: Jul 26, 2021

Last updated: Jul 26, 2021


Following the Grenfell Tower tragedy, there has been a significant shift in building practises and material specifications of high-rise balconies and terraces.

One of the main aims of BS 8579:2020 is to provide a standard that encourages the building of safer and more inclusive balconies and terraces. 


BS 8579 requires balconies on buildings, which are occupied, above 11 metres shall be of limited combustibility (i.e A1 or A2-S1-d0 as classified by BS EN 13501-1 in accordance with Regulation 7). Importantly, the standard introduces that this shall also apply to stacked balconies on buildings of any height. Emphasising that balconies should be built to prevent the spread of fire into the structure and surrounds.

This new rule for stacked balconies of any height is a significant change, yet it is a reasonable and acceptable instruction when seen in the perspective of increasing fire safety.


Water dripping has long been a source of concern for balcony specifiers and designers. As such, BS 8579 requires that balconies and terraces have some form of controlled drainage. 

BS8579 offers two methods of controlled drainage:

  • Pipe drainage, which usually drains back towards the building and into a downpipe (Although, drainpipes can be unattractive and prone to clogging). 
  • Edge drainage, which enables draining away from the building to the front edge of the balcony.


In addition to the well understood pendulum slip test requirement which measures macroroughness and requires a PTV of 36 even when wet there is additionally a requirement for Surface Microroughness (Rz) which is a component of surface texture.  A value of 20 or higher is required to pass, and the result is given as a single number.

BS8579 Decking Systems

EnviroBuild offers systems that comply entirely with all the above requirements on every type of balcony or terrace, with particular attention to the new drainage requirements.

Our 150 Aqua-Channel is an all-in-one, non-combustible aluminium decking system that features IP 56 tested innovative drainage.

This simple clipless system can remove the need for a soffit and still be fully compliant, thereby making it the most cost effective balcony solution available.

EnviroBuild also offer the industry leading Pro-Grip 145 that works perfectly with soffit drainage leaving 6mm gaps between boards

Finally EnviroBuild have porcelain system solutions available not just for recessed balconies and terraces, but also for open steel cantilevered balconies. This system is designed to work with porcelain or steel pavers providing the most complete set of solutions on the market.

While we are touching on some key points that relate to our products, the standard goes on to provide in-depth guidance for balconies and terraces in terms of spatial arrangement, wind effects, inclusive design, safety considerations, drainage, weathering effects, thermal and acoustic considerations.

If you are wanting more detailed information you can purchase the full BS 8579:2020 guide