The classification, side by side.
The typing system originates in the 2011 guidance Fire Safety in Purpose-Built Blocks of Flats (updated 2022) and is used across the residential sector, by lenders and by insurers. It answers two questions: does the assessment go beyond the common parts, and does it open up construction?
| Type | Scope | Destructive? | Typical trigger |
|---|---|---|---|
| Type 1 | Common parts only | No | Routine statutory compliance — the default for blocks of flats |
| Type 2 | Common parts only | Yes — sampled opening-up of construction | Reason to suspect defective compartmentation between flats and common parts (e.g. post-refurbishment doubt) |
| Type 3 | Common parts + flats (means of escape and detection within dwellings) | No | Concern about escape provision or alarm coverage inside flats — common in HMO-style conversions and social housing stock reviews |
| Type 4 | Whole building | Yes — in common parts and a sample of flats | Serious doubt about original construction or widespread unauthorised alteration; often follows a fire |
What Type 1 must still include
Type 1 is non-destructive but not superficial. Since the Fire Safety Act 2021 it must consider the external wall construction (which may require an EWS1 or FRAEW appraisal under PAS 9980 where cladding risk exists), all flat entrance doors opening onto common parts, and the building's evacuation strategy — stay put or simultaneous evacuation. A Type 1 that ignores external walls is not suitable and sufficient. See assessments in blocks of flats.
Access and cost implications of Types 3 and 4
Types 3 and 4 require access to dwellings, which leaseholders and tenants are not generally obliged to grant without lease provisions or agreement — assessments are usually done on a sample basis. Destructive types also carry making-good costs. This is why competent assessors recommend escalation only against a defined doubt, documented in the Type 1 report, rather than as a default. The cost guide covers typical pricing for each type.
Which type do you actually need?
- Purpose-built block, no known defects: Type 1, reviewed annually or after change.
- Converted building (house-to-flats), unknown separation quality: Type 1 initially; assessor may recommend Type 3 to verify in-flat escape and detection.
- Post-refurbishment where fire-stopping quality is in doubt: Type 2 sampling of the affected areas.
- History of unauthorised works, or post-fire investigation: Type 4.