Types of Fire Risk Assessment: The Difference Between Type 1, 2, 3 and 4

If you manage a block of flats, an HMO or any multi-occupied residential building, you will have been quoted for a "Type 1" or asked whether you need a "Type 4". The terminology is specific to housing, it is widely misused and choosing the wrong type is one of the more expensive mistakes in the sector.

This guide explains all four types as defined in BS 9792:2025, the current code of practice for fire risk assessment in housing, which came into effect on 31 August 2025 and supersedes the withdrawn PAS 79-2:2020.

The two variables

Every type is a combination of just two decisions:

1. How much of the building is inspected: the common parts only or the common parts and a sample of dwellings.
2. Whether the inspection is intrusive: whether construction is opened up or only what is visible is examined.

That gives four combinations.

Note the ordering. Type 2 is not "one step better" than Type 1 in a linear sense. Type 3 covers more of the building than Type 2 but does so without opening anything up. They answer different questions.

Type 1: common parts, non-intrusive

This is the baseline assessment and it is the right answer for most buildings.

BS 9792:2025 describes the Type 1 as the basic assessment, generally sufficient for most buildings where there is evidence of the integrity of the building. It does not involve opening up work such as cutting holes in or removing walls, ceilings or partitions.

A properly conducted Type 1 is more thorough than most people assume. It includes:

• Means of escape from the common parts and the protection of escape routes
• Fire detection and warning and the evacuation strategy
• Emergency escape lighting, signage and firefighting equipment
• A full and thorough visual inspection of reasonably accessible compartmentation and other passive measures
• Examination of at least a sample of flat entrance doors. Common practice is to check around 10% of dwelling entrance doors, with a minimum of two
• Roof voids, where the building has a pitched roof, unless access is impractical, in which case that must be recorded
• The separating construction between dwellings and common parts so far as reasonably practicable and without opening up, including fire stopping within sample locations in service risers
• Lifting a sample of demountable false ceiling tiles in common parts where present and opening a sample of service riser doors where access is practicable
• Consideration of external wall construction, including cladding and attachments such as balconies
• Fire safety management, records, testing and maintenance regimes

The external wall point

BS 9792:2025 gives useful clarity here. Where the external walls are traditional masonry, meaning two leaves of masonry, a solid masonry leaf, solid concrete or stone, without attachments likely to result in serious risk of external fire spread, it is normally reasonable to assume the fire risk associated with the external walls is acceptable without further investigation and to record that in the assessment.

For other forms of external wall construction, a fire risk appraisal of external walls to PAS 9980 may be appropriate. That is a separate specialist instruction, not part of a Type 1.

The catch on evidence

The Type 1 is sufficient "where there is evidence of the integrity of the building". That evidence might come from visual inspection, previous structural or compartmentation surveys, previous intrusive inspections or information about the building's design and construction standards.

Where that evidence is not available, BS 9792:2025 says a Type 1 might not be appropriate. In a building with no records, unknown alteration history and visible signs of poor workmanship, an assessor who quietly signs off a Type 1 has not applied the standard.

Type 2: common parts, intrusive

The scope and objectives are broadly the same as a Type 1 but with additional intrusive inspection on a sampling basis. This usually requires a contractor to attend, to open up construction and to make good afterwards. The Control of Asbestos Regulations 2012 will normally be engaged.

To check the integrity of separating construction, the areas opened up might sometimes include a sample of dwellings, even though the assessment is otherwise concerned with the common parts.

BS 9792:2025 is explicit about when this is appropriate. A Type 2 is:

• usually a one-off exercise
• carried out only if there is good reason to suspect serious structural deficiencies that could lead to spread of fire beyond the dwelling of origin
• sometimes identified as necessary by a Type 1 but "ought not to be recommended as a matter of course"

That last phrase is worth quoting to anyone who has received a Type 1 report recommending intrusive investigation on every building in a portfolio. Blanket recommendations of that kind are a marker of an assessor who has not exercised judgement.

Type 3: common parts and dwellings, non-intrusive

A Type 3 includes everything in a Type 1 and then extends into at least a sample of the dwellings themselves, without opening up construction.

It considers the provision, arrangement and maintenance of fire precautions within the dwellings that are within the control of landlords, leaseholders, other duty holders or occupiers and it considers alterations or actions by residents that could compromise those precautions. Fire prevention measures are not generally considered unless they are within a duty holder's control, such as maintenance of electrical and heating installations.

Matters typically considered include:

• Integrity of fire-resisting elements between the dwelling and other dwellings
• Maximum travel distance from any point within a flat to the flat entrance door
• Protection of internal hallways, where relevant
• Ease of opening of the dwelling entrance door, which is a frequent and serious finding
• Fire safety of inner rooms
• Means of escape from upper levels of maisonettes
• Electrical and heating installations provided by duty holders
• Provision of smoke and heat alarms
• Provision of sprinkler or water mist systems

BS 9792:2025 also notes that a Type 3 gives an opportunity to advise duty holders, leaseholders and occupiers on best practice going beyond the legal minimum, for example additional alarms beyond those required by the Smoke and Carbon Monoxide Alarm (England) Regulations 2015.

A Type 3 is generally the right answer for tenanted stock, where the landlord has both control of and access to the flats and for buildings where resident alterations are a known concern.

Type 4: common parts and dwellings, intrusive

Same scope as a Type 3, with intrusive inspection in both the common parts and the dwellings, on a sampling basis. Contractor attendance, asbestos management and making good all apply.

BS 9792:2025 describes it as the most comprehensive assessment but is equally clear that it is "only appropriate in unusual circumstances". The example given is where a new landlord takes over a building whose history of works is unknown and there is reason to suspect serious risk to residents from both a fire in their own dwelling and a fire in a neighbour's.

As well as the safety of residents in a fire in their own dwelling, a Type 4 considers the potential for fire to spread from that dwelling to others, examining routes including riser shafts within dwellings, bathroom and kitchen extract ducts, drainage pipework and penetrations for gas and electrical services.

Choosing the right type

Work through these questions in order.

1. Do you have credible evidence of the building's compartmentation integrity? Original construction drawings, a documented fire strategy, records of previous intrusive surveys or a known and reliable construction standard. If yes, a Type 1 is a reasonable starting point.

2. Is there any reason to suspect serious structural deficiency? Signs include: unknown alteration history, evidence of unrecorded works, a building type with known systemic issues, visible fire stopping defects at accessible locations such as riser cupboards or an incident in which fire or smoke spread further than the compartmentation should have allowed. If yes, intrusive investigation is indicated, meaning Type 2 or Type 4.

3. Do you have control over and access to, the dwellings? Housing association and local authority stock, tenanted private blocks and HMOs generally do. Leasehold blocks generally do not or only with difficulty. Where you do and where conditions inside the flats materially affect risk, Type 3 is appropriate.

4. Is there a known problem inside the flats? Reports of removed or wedged flat entrance doors, resident alterations, poor electrical condition, hoarding or a vulnerable resident profile all point towards a Type 3 as a minimum.

5. Are you newly responsible for a building you do not know? This is the classic Type 4 scenario in BS 9792:2025 and the one occasion where the most comprehensive assessment is genuinely proportionate.

When to upgrade from Type 1

Upgrade when the Type 1 itself identifies the need and the identification is reasoned rather than routine. Legitimate triggers include:

• Fire stopping defects found at accessible sample locations, suggesting a systemic problem
• No evidence available of construction standards or alteration history
• Fire or smoke spread beyond a single dwelling in an actual incident
• Riser or roof void inspection revealing missing or breached compartmentation
• Change of ownership or management with no golden thread of building information
• Planned major works that will expose construction anyway, making intrusive inspection cheap to add

What the type does not tell you

Three common misunderstandings worth correcting.

The type does not indicate quality. A poorly executed Type 4 is worth less than a thorough Type 1. The type describes scope, not competence.

The type does not replace an external wall appraisal. None of the four types is a substitute for a fire risk appraisal of external walls to PAS 9980 where one is indicated.

The type does not cover the commercial parts of a mixed-use building. BS 9792:2025 applies to housing. The commercial parts require assessment to PAS 79-1:2020. A mixed-use building needs both.

On terminology

BS 9792:2025 makes a practical point about reporting: where terms such as "Type 1" are used, the report should include an explanation of what they mean and where they come from. The types originate from the LGA guide Fire safety in purpose-built blocks of flats and are now set out in BS 9792:2025. A report that uses the label without defining it is not helping the duty holder or anyone auditing them.

Frequently asked questions

Which type of fire risk assessment do I need for a block of flats? For most purpose-built blocks with evidence of construction integrity, a Type 1. Where you control and can access the flats or where conditions inside them affect risk, a Type 3. Types 2 and 4 are for cases where there is specific reason to suspect serious structural deficiency.

Is a Type 4 fire risk assessment a legal requirement? No. There is no legal requirement for any particular type. The requirement is that the assessment is suitable and sufficient. BS 9792:2025 is clear that a Type 4 is appropriate only in unusual circumstances.

How often do I need a Type 3 or Type 4? Types 2 and 4 are generally one-off exercises. Types 1 and 3 form part of the ongoing cycle of assessment and review.

Do I need to get inside every flat for a Type 3? No. Types 3 and 4 are carried out on a sampling basis. The sample size should be proportionate and should be stated in the report.

What is the difference between a Type 4 assessment and a compartmentation survey? A Type 4 is a fire risk assessment that includes intrusive inspection. A compartmentation survey is a focused technical survey of fire-resisting construction, usually producing a defect schedule rather than a risk rating and action plan. The two complement each other.

Which type covers cladding? None of them in full. All four require consideration of external wall construction but where the walls are not traditional masonry, a separate fire risk appraisal of external walls to PAS 9980 may be needed.