A very large proportion of the UK's building stock has no fire strategy. Buildings constructed before regulation 38 came into force in 2007 were under no obligation to hand one over. Buildings that did have one have lost it through sale, insolvency, change of managing agent or a filing cabinet that went in a skip.
That is a manageable problem right up until the moment it is not. This explains when it becomes urgent, what a retrospective strategy involves and what you get.
What a retrospective fire strategy is
A retrospective fire strategy, sometimes called an as-built or reconstructed fire strategy, establishes the fire safety design basis of an existing building from survey and investigation rather than from design documentation.
It answers questions that ought to have been answered when the building was built:
- Where are the compartment lines and what fire resistance do they achieve?
- What is the evacuation strategy and what does it depend on?
- What are the actual travel distances and are they acceptable for this occupancy?
- What is the exit capacity and what occupancy does it support?
- Why is the alarm the category it is?
- What are the fire safety systems for and what do they compensate for?
- What must the building's operators do to keep the design valid?
It is a different exercise from a fire risk assessment, which evaluates operational risk against benchmarks. A retrospective strategy establishes what the benchmarks should be for this particular building.
When you need one
You have inherited a building and have nothing
New freeholder, new managing agent, corporate acquisition, portfolio purchase or a residents' management company or right to manage company taking over from a developer that has since dissolved.
Note that since 1 October 2023, Article 22A of the Fire Safety Order requires an outgoing responsible person to give information to an incoming one. If you took over after that date and received nothing, that is a live compliance issue for the outgoing party and a gap for you.
You are about to alter the building
This is the most common and most avoidable trigger. Someone is about to remove a wall, form an opening, add a mezzanine, subdivide a floor plate or decommission a system and nobody can say whether that wall is a compartment wall or whether the system was compensating for something.
Altering a building whose design basis you do not understand is how compartmentation gets destroyed. It is also how a project ends up in front of building control with an enforcement problem rather than an approval.
Your fire risk assessment keeps hitting the same wall
The first of the nine steps in PAS 79-1:2020 and BS 9792:2025 is obtaining information about the building, including the fire strategy where a documented one exists. BS 9792:2025 notes that other than in small simple premises, the strategy is likely to be of value to the assessor.
Without it, the assessor is inferring design intent from what they can see and both standards require the assessment to record any significant areas that could not be accessed and to justify where a measure departs from current guidance but no upgrade is recommended. That justification is much harder to write when nobody knows what the original standard was.
BS 9792:2025 sets out a decision logic for buildings that do not conform to current standards: establish whether the precautions meet current standards, if not, whether they met the standards at the time of construction, identify shortcomings against both, then ask whether the departures create unacceptable risk. It states that in carrying out an assessment of premises constructed before the introduction of current standards, the assessor should have at least a basic understanding of the standards applicable at the time of construction.
You cannot apply that logic without knowing what the building was designed to.
Due diligence
Buyers' solicitors, lenders and institutional investors ask for the fire strategy and the regulation 38 information. Its absence generates enquiries, delays, retentions and price adjustments. Producing a retrospective strategy before going to market is usually cheaper than negotiating over its absence.
You suspect the building does not comply
Signs include: fire spread beyond a single compartment in an actual incident, fire stopping defects found at accessible sample locations, evidence of unrecorded works, a building type with known systemic issues or a fire risk assessment that has recommended intrusive investigation.
Higher-risk buildings
For buildings at least 18 metres or at least seven storeys with two or more residential units, the Building Safety Act 2022 regime requires a golden thread of building information, created, stored and updated throughout the building's lifecycle and a safety case demonstrating that building safety risks are being managed. A building with no documented fire strategy has a golden thread with a hole at the start of it.
Insurance
Underwriters increasingly ask what the building is, how it is constructed and what the fire strategy is. "We do not know" is an answer that affects terms.
What the process involves
The scope scales with the building but the shape is consistent.
1. Desktop review
Everything that exists is gathered: any drawings, planning history, building control records held by the local authority, previous fire risk assessments, compartmentation or fire door surveys, system commissioning certificates and servicing records, asbestos surveys and any correspondence with the fire and rescue authority.
Local authority building control archives are frequently more productive than clients expect, particularly for buildings from the 1980s onwards. Approved inspector records are harder and where an approved inspector has ceased trading they may be gone entirely.
2. Establish the era and the applicable standards
Knowing when the building was built and under which edition of the Building Regulations or predecessor legislation, tells you what it was probably designed to. That matters because, as BS 9792:2025 puts it, standards improve over time but that does not imply older standards are unsafe and upgrading to current standards may fail the test of reasonable practicability or be architecturally impossible.
3. Physical survey
Measured survey where drawings are absent or unreliable. Then:
- Travel distances measured, not scaled from a drawing that may not reflect the building
- Exit widths and capacities measured
- Compartment lines traced so far as visible, including above suspended ceilings, in risers and in roof voids
- Fire doors sampled and their locations recorded
- Systems identified and their coverage established
- Stairs, lobbies, protected routes and final exits recorded
- External wall construction observed so far as possible
4. Intrusive investigation, where needed
Opening up at sample locations to establish separating construction, fire stopping and cavity barriers. This engages the Control of Asbestos Regulations 2012 and requires a contractor for opening up and making good.
Intrusive work should be targeted, informed by the non-intrusive survey and proportionate. It is expensive and a strategy that recommends blanket opening up across an entire building without a reasoned basis is usually the wrong answer.
5. Analysis
Comparing what is there against the standards of the era and against current guidance and identifying where the building sits. This is where the professional judgement lies: distinguishing genuine deficiency from acceptable historic departure.
6. The document
A fire strategy for the building as it actually is, covering the same ground as a new build strategy: design basis, occupancy, evacuation strategy, means of escape, compartmentation, detection and alarm, suppression, smoke control, external fire spread, fire service access and the management arrangements the strategy depends on.
Plus, critically, a statement of what could not be established and what would be required to establish it.
Two things a good retrospective strategy will do
It will state its own limitations. A retrospective strategy built on a non-intrusive survey cannot confirm concealed construction. Saying so is not a weakness, concealing it is.
It will not recommend upgrading everything to current standards by default. BS 9792:2025 is explicit that a departure from prescriptive guidance is not, alone, sufficient justification for upgrading work and that the crux is determining whether departures create unacceptable risk. A retrospective strategy that concludes "bring the whole building up to Approved Document B" has not done the analysis. It has avoided it.
What you get out of it
- A defensible baseline. You know what the building is designed to do and what that depends on
- A change control reference. Every future alteration can be checked against it
- A better fire risk assessment. Your assessor stops inferring and starts assessing
- Faster due diligence. The question gets answered before it is asked
- Golden thread content, for higher-risk buildings
- A basis for prioritising spend. Knowing which departures matter and which do not is the difference between a proportionate programme and a panic
What it is not
It is not a certificate of compliance. A retrospective strategy describes and analyses, it does not retrospectively approve work that was never approved. Where unauthorised building work is identified, that is a separate matter and note that the Building Safety Act 2022 extended the time limit for a section 36 notice requiring removal or alteration of non-compliant work from 12 months to 10 years.
It is not a fire risk assessment and does not discharge your Article 9 duty.
It is not a substitute for a PAS 9980 external wall appraisal where one is indicated.
Frequently asked questions
How far back can building control records be traced? Local authority archives are often good from the 1980s onwards and sometimes earlier. Coverage varies considerably by authority. Approved inspector records are less reliable, particularly where the inspector has ceased trading.
Do I need intrusive investigation? Not always. Where there is credible evidence of construction integrity, a non-intrusive strategy with clearly stated limitations may be sufficient. Where there is reason to suspect serious deficiency, targeted opening up is the only way to establish the position.
Will a retrospective strategy tell me my building is non-compliant? It may identify departures from current guidance. That is not the same as non-compliance and BS 9792:2025 is clear that a departure alone is not sufficient justification for upgrading. What matters is whether the departure creates unacceptable risk.
How long does it take? For a straightforward commercial building, typically a few weeks including survey. For a large or complex building requiring intrusive investigation and contractor attendance, considerably longer.
Can my fire risk assessor produce it? Not necessarily. It is a fire engineering exercise rather than a risk assessment. Ask directly whether the provider undertakes fire strategy work and what qualifications the author holds.
Does a retrospective strategy satisfy Regulation 38? Regulation 38 applies to building work. A retrospective strategy does not retrospectively discharge a duty that was owed by someone else at the time. It does give you the information regulation 38 was intended to put in your hands.
