Building Assessment Certificate: transitional arrangements for existing buildings: factsheet

Updated 5 April 2022

This guidance was withdrawn on

This guidance is withdrawn as it is no longer current. Please see the latest guidance on the Building Safety Act.

What are we going to do?

We are introducing a new regulatory regime which ensures that building-safety risks are being actively managed in a proportionate way. In this factsheet, ‘high-rise residential buildings’ means those with at least two residential units and that are at least 18 metres in height or at least 7 storeys.

The Building Safety Regulator will be responsible for carrying out checks to make sure that the people who are responsible for occupied high-rise residential buildings, the Accountable Persons, are managing building safety risks, complying with their duties under the new legislation, and keeping residents safe.

After a building has been registered, the Building Safety Regulator will periodically assess Accountable Persons’ performance through the Building Assessment Certificate process. Once directed to apply for a Building Assessment Certificate, the Principal Accountable Person will send a suite of documents to the regulator. The documents will show how the Accountable Persons are managing their building safety risks and keeping residents safe.

The regulator will examine these documents and may send an inspector to the building to verify the Accountable Persons’ arrangements for managing building safety risks. If satisfied, the regulator will issue a Building Assessment Certificate for the building. You can find out more about this in the Registration and Certification factsheet.

There are estimated to be around 12,500 occupied high-rise residential buildings in England. It will take around five years for the Building Safety Regulator to assess the performance of the Accountable Persons for these existing buildings for the first time, alongside any new buildings that come into scope in the same period. This factsheet describes the principles that the Building Safety Regulator will follow when prioritising the first assessment of these existing buildings.

Accountable Persons will be under ongoing duties to proactively assess and manage building safety risks. This applies while the regulator is working through applications for Building Assessment Certificates for occupied buildings for the first time.

How are we going to do it?

Prioritisation for first assessment

Existing buildings will be placed into groups or ‘tranches’ for assessment. These will be based on the height of the building and the number of dwellings it contains, so the tallest buildings with the greatest number of dwellings will be placed into the earlier tranches. The regulator will also have the option, following receipt of information at registration, and in strictly defined circumstances, to move buildings between tranches; for example, buildings with unremediated ACM cladding will be assessed in the first tranche, regardless of height or number of dwellings. The regulator aims to assess all buildings for the first time within five years.

The table below details the tranches and their order of assessment. Height is measured in metres and the number of dwellings includes any flats or apartments in the building, whether or not they are currently occupied.

To use the table, find the building height in the left-hand column and follow the line across to the column with the relevant total number of dwellings in the building; the number in the box is the tranche number. For example, a 35-metre building with 60 dwellings is in tranche 2.

Accessible version of the table

Height of building (in metres) No. of dwellings: 141+ 74-140 54-73 49-53 26-48 11-25 2-10
50+ m 1 1 1 1 1 1 5
30-49 m 1 2 2 3 3 3 5
18-29 m 1 2 3 3 4 5 5

Criteria for prioritising within tranches

The Building Safety Regulator proposes to follow a hazard-based approach to prioritising assessments within tranches that reflect the potential to cause harm to people and the consequences of an incident, were a serious fire or structural failure to occur. Buildings with multiple hazard factors are likely to be assessed earlier in each tranche.

The hazard-based prioritisation criteria are currently being developed using multiple information sources. The regulator is also consulting with stakeholders, including drawing on the Building Risk Review carried out by the Fire and Rescue Services.

Prioritisation factors will be considered in combination and might include, for example, presence of a single staircase and no sprinklers, previous refurbishments that crossed multiple floors such as replacement heating, the hazards from mixed-use of a building (e.g. commercial businesses), and the type of external wall system.


Following the initial assessments, the Building Safety Regulator will reassess Accountable Persons’ management of building safety risks at least every five years. Some may be reassessed earlier than the five-year limit.

The timing for being called for reassessment will depend on a set of criteria which are currently in development. Factors that could lead to more frequent reassessment include, past performance in the assessment process, a change in Accountable Person, a significant refurbishment, or other intelligence from sources such as complaints raised by residents.

Next steps

The Building Safety Regulator’s final approach to tranching will be set out in its Strategic Plan. This plan will be subject to consultation and will be published after the Building Safety Bill achieves Royal Assent.


Under the new building safety regime, all occupied high-rise residential buildings will need to be registered with the Building Safety Regulator. To register the building, the Principal Accountable Person must provide important details about the building. This information across occupied high-rise buildings will give the Building Safety Regulator the necessary information it needs to prioritise effectively.

The Building Safety Bill gives the Building Safety Regulator the power to tell the Principal Accountable Person when they need to apply for the Building Assessment Certificate. This is done by means of a ‘call-in notification’. The Principal Accountable Person must apply for the certificate within 28 days of the call-in notification being given.

When will buildings start to be assessed?

The Building Safety Regulator will begin calling in applications for the Building Assessment Certificate once registration of all existing occupied high-rise residential buildings is complete.

We recognise that Accountable Persons will need time to understand their new responsibilities and prepare the required documents. There will, therefore, be a gap between the new regime coming into force and the first buildings being called in for the Building Assessment Certificate. We want this to be as short as possible but expect this gap to be no longer than 6-12 months. We expect that it will take around five years for all existing occupied buildings to be initially assessed.

On receipt of an application, the Building Safety Regulator will examine the documents provided in the application by the building’s Principal Accountable Person to establish whether those responsible for the building are managing its building safety risks.

It is the duty of the Accountable Persons to assess and manage the building safety risks at all times, not just when called in to apply for an assessment by the regulator.

When will my building be assessed for the first time?

Existing occupied high-rise residential buildings will be assessed initially over a period of five years.

The Building Safety Regulator will call in new buildings for assessment for the first time within six months of occupation.

Other existing buildings, for example those which have gone through a change of use (e.g. an existing block of offices converted into flats) will be called in for assessment for the first time within six months of occupation.

How often will my building be assessed?

All high-rise residential buildings will be reassessed regularly.

The Building Safety Regulator will determine a set of criteria for reassessment. This means that the frequency of assessments will depend on a set of criteria including hazard factors, performance of Accountable Persons and effectiveness of safety management systems.

Key facts

  • There are estimated to be 12,500 existing buildings within scope of the building safety regime (at least 18 metres or at least seven storeys in height, with at least two residential units).

  • We estimate 1,500 (12%) residential buildings are seven storeys but under 18 metres in height, 7,000 (56%) buildings are between 18 metres and 29 metres and the remaining 4,000 (32%) buildings are 30 metres or more in height.