Compartmentation Surveys — Type 1 to Type 4 Explained
Compartmentation is the invisible fire safety control. Decades of M&E works, refurbs and lazy reinstatement turn fire-resisting walls into Swiss cheese. Compartmentation surveys are how you find — and fix — the holes.
What compartmentation actually does
Compartmentation is the use of fire-resisting walls, floors and doors to divide a building into compartments that contain a fire long enough for occupants to escape and for the fire brigade to intervene.
In a residential block, compartmentation underpins the Stay-Put strategy: if a fire in flat 3 is properly contained, residents of flat 5 can safely remain in their flats until the fire is extinguished.
When compartmentation fails — gaps around services, damaged fire doors, missing cavity barriers — Stay Put becomes Simultaneous Evacuation, with all the resourcing and safety implications that follow.
The four survey types
Mirroring fire risk assessment types, compartmentation surveys come in four scopes:
- Type 1 — Non-destructive, visual only, accessible areas
- Type 2 — Sample opening-up of service penetrations and risers in common parts
- Type 3 — Type 1 + visual inside flats (limited)
- Type 4 — Full intrusive sampling of common parts AND inside flats
When each is appropriate
Type 1: baseline first survey. Always start here.
Type 2: triggered when Type 1 identifies likely concealed defects, particularly in older buildings with multiple service penetration histories.
Type 3: where resident-led modifications are suspected and Stay Put strategy is being validated.
Type 4: high-risk buildings, post-incident, or where the Building Safety Case demands intrusive evidence.
What surveyors look for
Common compartmentation defects:
- Unsealed service penetrations — cables, pipes and ducts passing through fire walls without intumescent sealing
- Missing cavity barriers — particularly around modern cladding systems
- Damaged fire doors — gaps, damaged seals, painted hinges, removed self-closers
- Combustible insulation in voids — particularly above suspended ceilings
- Modifications without reinstatement — IT installs, plumbing changes, refurbishments
The third-party certification question
Reinstating compartmentation must be done by a third-party accredited installer using certified products. Accreditations to look for:
- IFC Certified (Installer scheme)
- FIRAS (Installer competence)
- LPCB LPS 1531 (Product certification)
Walking into a building and seeing intumescent sealant smeared around penetrations is not evidence of competent reinstatement — it must be tied to a certified installer's record card.
Documentation as evidence
Under the Building Safety Act 2022 Golden Thread, compartmentation evidence is a core requirement for any HRB. A defensible record includes:
- Survey reports (all types delivered)
- Marked-up drawings showing fire compartment lines
- Photographic evidence at every penetration
- Installer record cards for every reinstatement
- Product data sheets and test certificates
MetroFire delivers Type 1-4 compartmentation surveys and FIRAS-certified fire-stopping installs across London and the South East. Book a survey.
