The term “relevant building” defines a specific group of buildings based on factors including their height, use and the number of storeys. The term is used within the Building Regulations & Standards in England, Scotland and Wales to identify building types where certain external cladding products or systems (including insulation) must achieve a specified minimum reaction to fire performance. It is also used in the Building Safety Act 2022 to identify buildings where additional leaseholder protections apply.
It is important to be aware that the definition of a “relevant building” differs between these documents. For this reason, it is essential to confirm you are using the correct definition for your application.
In this article, we’ll look at these definitions and how they’re applied.
Building Regulations in England and Wales
Regulation 7 of the Building Regulations 2010 in England and Wales states the requirement that external sufaces and insulation, or specified attachments, used in the external walls of a relevant building are of European Classification A2-s1,d0 or A1. This is a regulation that must be met.
Learn more about Euroclass ratings.
It defines a “relevant building” as a building with a storey (not including roof-top plant areas or any storey consisting exclusively of plant rooms) at least 18 metres above ground level (measured from the lowest ground level adjoining the outside of a building) which contains:
- one or more dwellings;
- an institution; or
- a room for residential purposes.
In addition, the guidance in Approved Document B for England states that insulation materials used as part of the external wall construction on buildings above 11 metres that include a ‘residential’ purpose (purpose group 1 and 2) should achieve a Euroclass rating of at least A2-s1,d0. The same applies in Wales as of December 2025. This is guidance and other insulation materials could be used if an alternative route to compliance is adopted (this could be using a BS 8414 tested construction, an assessment to BS 9414 in lieu of a test, or a fully fire engineered solution). Learn more about Kingspan BS 8414 tested systems.
These purpose groups are set out below:
The above restrictions do not apply to cavity wall insulation where min. 75 mm thick brick or concrete leaves are used with suitable cavity barriers around all openings and at the top of the wall. They also do not apply to insulation and water proofing materials used below ground level or up to 300 mm above that level.
Building Standards in Scotland
Regulation 8 of the Building (Scotland) Amendment Regulations 2022 states that materials which form part of an external wall cladding system, or specified attachment, of a relevant building are of European Classification A2-s1, d0 or A1, classified in accordance with BS EN 13501-1: 2018.
This requirement does not apply to insulation exposed in a cavity between 2 leaves of masonry or concrete (min. 75 mm thick), with cavity barriers around all openings and at the top of the wall-head. It also does not apply to insulation and water proofing materials used below the ground and up to 300 mm above the ground.
In Scotland a “relevant building” is any building which has or creates a storey (not including roof-top plant areas or plantrooms) at a height of 11 metres or more above the ground and which contains a:
- dwelling
- building used as a place of assembly, or as a place of entertainment or recreation
- hospital
- residential care building or sheltered housing complex
- shared multi-occupancy residential building
- hotel, guest house, boarding house or hostel.
Building Safety Act 2022 in England
The term “relevant building” is also used within the Building Safety Act to identify buildings where certain financial protections apply for leaseholders in England. This definition is not the same as that used for purposes of Building Regulations/Building Standards requirements.
The Building Safety Act in England defines Relevant Buildings as meeting the following criteria:
- at least 11 metres in height or has at least five storeys (whichever is reached first)
- contains at least two dwellings
- not a leaseholder-owned building.
For further information on the Building Safety Act take a look at our blogs or book a CPD session.
