Block of flats buildings insurance turns on one number more than any other, and it is the number nobody in the building can produce from memory. The rebuild cost of a block is not its value, not the sum of the flats' prices, and not last year's figure with a bit added. Getting it wrong is not a rounding problem, because underinsurance is settled by averaging and that reduces every claim, including the small ones nobody expected to test it.
What a reinstatement cost assessment actually counts
Demolition and clearing the site. Rebuilding the structure to current building regulations, which is usually more demanding than what stands. Common parts, stairwells, lifts, tanks, pumps and plant. Professional fees for architects, engineers and building control. Scaffolding and access. The result is routinely higher than owners expect, and on older blocks it is often several times what anyone had guessed.
Why blocks drift out of date faster than houses
Construction cost inflation, changes to fire safety and building regulation requirements, and improvements made to the block between valuations all push the figure up, while index linking applied to a starting number that was wrong only makes a wrong number bigger. A professional assessment every few years resets it; index linking between assessments keeps it roughly current.
How averaging bites
If the block is insured for half its rebuild cost, the insurer may settle a claim at half its value, whatever the size of the claim. A leak that costs a modest sum to repair is halved exactly as a fire would be. That is why the sum insured matters to residents who will never see a total loss, and why a committee that skips the valuation is taking a risk on every future claim.
Who has to care, and what they should ask for
The freeholder or management company arranges the policy and carries the duty to insure properly. Leaseholders pay for it and can ask to see the policy, the premium and the basis of the sum insured. A committee taking over a block should ask for the last reinstatement assessment by date, and if there is not one, commission it before renewing.
Questions people ask about block of flats buildings insurance
How is the rebuild cost of a block calculated?
By a professional reinstatement cost assessment covering demolition, clearance, rebuilding to current regulations, common parts and plant, and professional fees. It is not the market value of the flats.
How often should a block be revalued?
A full assessment every few years, with index linking in between. Construction costs and regulatory requirements both move faster than owners expect.
What happens if the block is underinsured?
Claims can be settled proportionally, so a building insured for half its rebuild cost may see every claim halved. It applies to small claims as well as total losses.
Can leaseholders ask how the figure was set?
Yes. Leaseholders may inspect the policy and supporting documents and challenge an unreasonable service charge, and the basis of the sum insured is a fair question to put to the managing agent.