Fire Compartmentation
Changes to "Fire Safety: Approved Document B 2019 with Amendments Issued - A Review by Bauder Ltd"
The above document contains a section entitled "Compartmentation - Junction of Compartment Wall with Roof", which explains that there has historically been differing interpretation regarding the requirements at roof level where a compartment wall passes beneath the roof construction.
In most cases, including many Building Control authorities, the accepted position has been that where a roof build-up can be demonstrated as achieving BROOF(t4), no further consideration is normally required unless the deck itself is combustible and the building exceeds 15m in height. However, there has always been a minority view among some Building Control authorities that additional measures may be required.
What Has Changed?
Bauder is increasingly seeing Building Control interpretations becoming more cautious, with some authorities now requiring a non-combustible fire stop above the deck for the width of the compartment wall, typically within the insulation layer itself.
Whilst Bauder may hold a strong technical opinion regarding when this measure is or is not necessary, our advice remains that Building Control should always be consulted on the specific project.
The challenge is that the interpretation cannot always be predicted in advance. Historically, the long-established practice of achieving BROOF(t4) was generally considered sufficient. However, there is now a greater risk that Building Control may require additional compartmentation measures if consulted later in the project process.
Where requirements are not addressed, Building Control may require remedial action and could impose penalties for continued non-compliance after a specified date.
Why Is This Important?
This issue is particularly relevant on refurbishment projects, where there may be limited information available regarding the existence, location or orientation of compartment walls beneath the roof construction.
Because of this changing approach, Bauder has revised its advice process for refurbishment projects. Going forward, specifications and survey reports will include standard wording advising that Building Control should be consulted regarding the roof-over-compartment-wall situation.
Contractors are also advised to bring this matter directly to the attention of designers, clients and contractors at the earliest possible opportunity.
Standard Specification Wording
Fire Regulations - Compartmentation
Approved Document B Vol 1: Dwellings Section 5 Internal Fire Spread covers Compartmentation (Compartmentation is covered in Section 8 of Vol 2: Buildings Other Than Dwellings and, for Scotland, Wales and Northern Ireland, similar considerations are necessary for both Dwellings and Buildings Other Than Dwellings) and there is a consideration to be made if the roof goes over a compartment wall.
For new build projects we would expect the Principal Designer to establish Building Control requirements and notify accordingly. For refurbishment projects it is not always straightforward for the roofing team to establish whether a compartment wall exists beneath the roof and its full orientation. Therefore, Bauder Ltd will rely on the specifier or client to advise if a known compartment wall is present beneath the existing roof.
As the requirements have proven to be open to various interpretations across Building Control authorities, Bauder's advice is to consult with the Building Control Officer responsible for the building.
New Build and Refurbishment Considerations
On new build projects it is generally reasonable to assume that the Principal Designer has considered compartmentation requirements. However, following the same consultation process used for refurbishment projects will not be detrimental and may help avoid future issues.
The cost implications of introducing non-combustible insulation in place of PIR insulation can be significant, particularly on tapered insulation schemes where practicality may dictate that all insulation is changed to non-combustible products.
Understanding Building Control's interpretation of requirements above compartment walls is therefore increasingly important to avoid unexpected costs, delays and contractual disputes.
Where consultation takes place early enough in the design process, there is often time to discuss and clarify requirements. The technical arguments outlined within Bauder's fire guidance document continue to be recognised and respected by many Building Control authorities.
Further Information
The Fire Safety: Approved Document B 2019 with Amendments Issued guidance can be viewed on our website:
https://www.bauder.co.uk/technical-centre/standards-and-knowledge/fire-protection-statement
The document is also attached to this Contractor Update.