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Balcony & terrace design: your questions answered

by Jennie Ward

Sarah Spink, CEO of the Liquid Roofing and Waterproofing Association (LRWA), explains how the new British Standard 8579:2020 is helping to clarify queries about balcony and terrace design.

Sarah Spink, CEO of the LRWA.

In September 2019, building regulations covering fire safety were amended and updated (Approved Document B). This stated that any products with membranes forming part of external walls on high-rise residential buildings need to meet the BS EN 13501-1 fire class requirements and achieve a result that deems them non-combustible.

The new rules apply to anything deemed as a ‘specified attachment’, which is defined as a balcony attached to an external wall, which means only non-combustible materials can be used for these structures. This led to lots of unanswered questions regarding the definition of the different types of balconies and roofs, and what falls under the ban. The launch of BS 8579 provides guidance on the design of balconies and terraces as well as their component parts. The document was released as approved British Standard guidance in August 2020.

What is the definition of a balcony?
BS 8579 defines a balcony as; ‘an accessible external amenity platform above ground level exterior to and with direct access from a building.’
The guidance also states that a balcony formed above an external space that is not a habitable room, is not regarded or designed as storage space and for the purposes of fire, a balcony is not a roof.

What is the definition of a terrace?
BS 8579 states a terrace is an ‘…external accessible surface above an internal space above ground level exterior to and with direct access from a building to occupants for purposes other than exclusively maintenance.’ It clarifies that a terrace is a roof for the purposes of fire and waterproofing, and can also perform the function of a floor. Certain spaces might incorporate features of both a balcony and terrace.

What materials and components can and can’t be used for balconies in respect to fire safety and regulation?
Only materials achieving class A1 or A2 – s1, d0, in accordance with BS EN 13501-1:2018 should be used for components of balconies on all buildings with an occupied floor over 11m above the lowest ground level – including the supporting structure in a free-standing balcony.

Components for balconies for all other buildings and arrangements should be risk assessed of fire spread, and reduced where possible within the design. If it is not possible to achieve all aspects of fire safety and performance using materials of at least class A1 or A2-s1, d0, minor components such as seals, gaskets, fixings, laminated glass, thermal breaks and membranes – which includes waterproofing membranes – could be exempt from this recommendation if a risk assessment proves adequate resistance to the spread of fire.

What materials and components can and can’t be used for roof terraces with respect to fire safety and regulation?
Roof terraces should be designed to mitigate the spread of fire on the terrace itself, or where a terrace is adjacent to another structure or a compartment within the building. To achieve this, the guidance advises the following:

1) As an occupied roof, a terrace performs the function of a floor. If this is over 11m above the lowest ground level build-up and within 3m of an extensive vertical facade above, it may be limited to classification BROOF (t4) in accordance with BS EN 13501-5:2016

2) A terrace containing planting may be divided by narrower strips of material achieving minimum classification BROOF (t4) in accordance with BS EN 13501-5:2016 in different orientations

3) A terrace containing planting may also be divided by walls of fire-resisting construction in different orientations.

The LRWA has worked closely with fellow trade associations to clarify how the regulations should be interpreted. For further advice on liquid waterproofing on new high-rise residential buildings and compliance with the regulations, please contact our technical team.

www.lrwa.org.uk

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