What is Approved Document B? – Important Updates for the Construction Industry

What is Approved Document B? – Important Updates for the Construction Industry

The Grenfell Tower incident shocked the country and the world, leading to many changes in both the fire safety and construction industries. Approved Document B is one such policy that has received major updates as a result of this incident, and as someone working in the construction industry, it’s essential you are aware of how this could impact your work. With changes already in place and needing to be implemented imminently we’re here today to share with you everything you need to know about Approved Document B.

What is Approved Document B?

The potential for a fire in a multi-storey building to break out through the facade and then to rapidly spread across external cladding is addressed in Approved Document B. This states that:

“The external envelope of a building should not provide a medium for fire spread if it is likely to be a risk to health and safety. The use of combustible materials in the cladding system and extensive cavities may present such a risk in tall buildings.”

Approved Document B addresses fire safety precautions which must be adhered to, to ensure the safety of occupants, firefighters and those close to the building in the event of a fire.

When were the changes made to Document B and what do they mean for the construction industry?

In June 2022, the Government released amendments to Approved Document B following the Grenfell Tower incident, to come into force on 1st December 2022, with a transition period of six months. Any new building application will, therefore, legally need to satisfy these changes after the 1st June 2023. This is why it’s so critical that you quickly get to work to make the necessary changes and adhere to this policy at all times.

There are many changes to consider for those in the construction industry. Some (but not all) of the key changes include:

  • The construction of external walls serving buildings over 11m in height has been included in the approved document, which restricts the use of combustible materials.
  • The use of combustible materials are banned in all residential buildings above a height of 11 meters and all buildings above six storeys.
  • The inclusion of hotels in the definition of relevant buildings.
  • Hotels over 11m in height will have to be constructed with external walls materials attaining A2s1d0 or better.
  • There will be a requirement for cavity trays in relevant buildings, other than those with masonry external walls to be non-combustible, this will become a legal requirement from December 2023.
  • Prior to December 2023, any combustible cavity trays acceptability will still be subject to analysis of the combustible components specified in the external wall in terms of size, number, position and orientation.
  • ACM with an unmodified polyethylene core has been banned from use on all buildings.

What is ACM?

Aluminium Composite Material (ACM) panels are commonly used for cladding buildings. Rainscreen cladding is a double-wall construction. The rainscreen itself provides a first barrier to rain water penetrating into the wall of a building.

ACM cladding consist of two skins of aluminium bonded to either side of a lightweight core of materials. It has traditionally been a popular product due to its light weight, wide range of colours and ability to form its shape to accommodate complex building designs. Unfortunately however, when exposed to fire, or extreme temperatures the panels can delaminate and expose the core material. Core materials can be combustible, hence fires can spread.

Why is ACM banned on construction projects?

ACM cladding became notorious following the Grenfell Tower fire on 14 June 2017, when ACM cladding with a polyethylene core was thought to have contributed to the rapid spread of the fire up the outside of the tower, which is why it’s now banned from use on all buildings. For anyone with this material present in their building currently, it’s recommended that a fire risk safety assessment is undertaken, with possible remediation work required thereafter.

What does the A1 material classification mean?

A1 rated products do not require additional safety tests given they are completely non-combustible. Examples of these materials include aluminium, natural stone, concrete and porcelain. These materials are only A-rated in their raw form e.g if they haven’t been treated at all.

What is A2?

This fire performance classification relates to materials that are classed as non-combustible in Scotland and of limited combustibility in England and Wales, emit little or no smoke and produce no flaming droplets or particles within the first 10 minutes of fire exposure.

What’s the difference between A1 and A2 Fire Rating?

In the UK, building regulations state that any high-rise building above 11 metres should not have combustible materials within the construction of external walls and specified attachments.

A1 materials are completely non-combustible while A2 materials have very limited combustibility. While A1 materials have no contribution to fire, A2 materials have limited contribution to fire. Stringent tests must be passed in order for construction products to reach a Class A rating. Understanding the differences between these two categories of materials is essential when starting a new construction project, as it will allow you to only choose materials that are safe for your building.

Here at Dortech Direct, we have hundreds of clients working in the construction industry who will need to make adjustments to their way of working following the changes to Approved Document B. Our aim is to help make this process as quick and easy as possible for you, so that you remain in compliance at all times and protect the residents in your building. We offer a range of fire retardant products, all of which can help to reduce the chance of fires or incidents in your building. Our team will be on hand at any time to help you find the right tools and materials for your next project and support you with these important changes to Approved Document B.

Check out the Fire Rated products available at www.dortechdirect.co.uk

Shop By Fire Rated Brands:

Arbo: Fire & Intumescent 

Everbuild: Fire Rated 



Sika: Passive Fire Protection