Converted vs Purpose-Built Flats Insurance
Two blocks with the same number of flats can be rated very differently depending on whether the building was designed as flats or converted into them.
Reviewed by the Landlord Quote editorial team · Last updated 14 September 2026
In short
- Converted buildings are usually older, with timber floors and higher escape-of-water exposure.
- Fire compartmentation between flats is a key underwriting question in conversions.
- Purpose-built blocks bring their own questions: cladding, lifts, communal plant and height.
- Both are commercial risks — neither is written on a standard home policy.
- Documentation about the conversion works often improves the terms available.
How do insurers treat converted flats?
As an older, generally higher-maintenance risk. Converted houses typically have timber floors and joists, original roofs, aged plumbing and fire compartmentation added retrospectively — all of which influence how an underwriter prices and what they ask for.
Escape of water is the single most common cause of loss in flats, and it is worse in conversions because water travels through timber floors into the flat below and into communal areas. Insurers often apply a higher escape-of-water excess in these buildings.
Compartmentation is the other recurring theme. In a purpose-built block, fire separation between flats is designed in; in a conversion it depends on what was done during the works and whether it has been maintained since. A current fire risk assessment addressing compartmentation is valuable at renewal.
Conversions above commercial premises are a separate category again, because the risk from the shop or restaurant below usually drives the rating.
Things to consider
- Keep records of when plumbing, wiring and the roof were last renewed.
- Listed status increases reinstatement cost and needs to be disclosed.
- Flat roofs, particularly older felt roofs, are commonly asked about and sometimes restricted.
Read next: Blocks with commercial units · Rebuild cost for a block
What do insurers ask about purpose-built blocks?
Height, number of storeys and units, construction of the external walls, cladding and balcony materials, lift and communal plant details, fire safety measures and the current fire risk assessment.
Building height drives a lot of the process. Buildings of at least 18 metres or seven storeys are higher-risk buildings with Building Safety Regulator duties, while buildings between 11 and 18 metres attract detailed external wall questions.
Where an EWS1 assessment exists, sharing it at enquiry stage usually widens the panel of insurers willing to quote. Where remediation is in progress, underwriters want the programme, funding position, interim fire safety measures and site security arrangements.
Read next: Blocks of flats insurance guide · Specialist block brokers
Can a converted flat be insured on a normal home policy?
The structure of a converted building containing separate flats is a block risk and is normally insured under a block buildings policy. An individual flat owner's home policy generally covers contents and their own fixtures, not the whole structure.
Some insurers do write buildings cover for a single flat in a small conversion where the leases require flat-by-flat insurance, but this is the exception and creates the gap and overlap problems described in our share of freehold guide.
Read next: Share of freehold buildings insurance
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