Fire Safety Guidance for Flat Roofs

Fire safety has always been an important part of any building project, including for flat roof build ups. In 2021, after two years of consultations, the fire safety guidelines have been updated. So what are the new regulations? And what do you need to know about flat roofs and fire safety?

Building Regulations and Fire Safety Guidance for Flat Roofs

Fire safety is well documented in the building regulations, even for flat roofing.
The Building Regulations Part B (Fire Safety) part B4 details the requirement of the external walls and roof of a building to adequately resist the spread of fire, and to prevent the spread of fire from one building to another. This becomes an important part of the roof construction and can influence design decisions too.
Section 10 of the same regulations explain how roof coverings will need to be fire rated. When looking at flat roofs, the covering will usually consist of the deck, vapour control layers, insulation, and waterproofing membranes.

Updated Guidance for Fire Safety Regulations

For more than two years, the Liquid Roofing and Waterproofing Association (LRWA), the Single Ply Roofing Association (SPRA) and the National Federation of Roofing Contractors (NFRC) worked together with the Ministry of Housing, Communities and Local Government (MHCLG) to create the Approved Document B. Released in 2021, this document focuses on fire safety and amendments have been made to this after the Government’s ban on using combustible materials in the external walls of high rise residential buildings of 18 metres and over.

What is Approved Document B and What Does this Mean for Fire Safety?

Approved Document B discusses and explains changes to fire safety legislation, and answers some of the questions that have emerged regarding the new regulations on flat roofing and waterproofing membranes, and fire safety.
Approved Document B now states 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 document also offers clarity and support for interpreting the new guidance in terms of ‘specified attachments’ and roofs that connect to external walls. The guidelines make it clear that a ‘Specified Attachment’ is a balcony or solar panel attached to an external wall, and details how waterproofing membranes can be used on balconies, and how this differs from a roof terrace. Using insulation to create a ‘thermal break’, is also discussed.

How are Roof Coverings Rated for Fire Safety?

Rating the fire safety of different products used in a flat roof build up is something that is taken very seriously. The performance of these products is assessed through a range of testing, and this will equate to a rating or Class. These consist of two letters, one for each of the two tests. These ratings or Classes correspond with the requirement to prevent a) penetration of fire and b) spread of flame into the building below. As a result, each of the letters can be A, B, C or D giving a combined classification from AA to DD. Within these ratings, A is ranked as the highest class and D is identified as the lowest. Using products for any flat roof build up that meet or exceed the standards required is a necessity for any property.

What are the Wider Considerations for Flat Roofing Fire Compliance?

Beyond using the correctly rated products for your flat roof, there are a number of steps that you can take to ensure flat roofing fire compliance. These include:
  • Being prepared for fire testing- project specific fire testing requests are on the rise from fire offices, and this can result in a longer time frame being required for any roofing project, which is not ideal. Being prepared for this through early engagement and asking this question early on is worthwhile. In many cases, the data from indicative tests should be sufficient.
  • Design best practices- in terms of flat roofing design, fire compliance can have an impact on best practices, making it more difficult to achieve best practice designs in specific areas like upstands. One example of this is the use of non-flammable insulation, which typically has an increased depth. As a result, for full fire compliance and great roofing design, these issues should be ironed out in the planning phase, so that top quality results won’t compromise the necessary fire safety, and vice versa.
For more information about fire safety guidance for flat roofs, or for professional single ply roofing installation, get in touch with leading experts here at Enviroply Roofing.