Answer: Most residential leases forbid alterations to a leasehold flat without the consent in writing of the freeholder, though many will state that such consent must not be unreasonably withheld. Find out if consent/licence for alterations was granted.
If it was, at that time the freeholder should have considered whether the leases in the building needed to be varied by adjusting the service charge payable to reflect the new structure and cover expenses such as the upkeep of the roof of the new extension, or whether the responsibility was to be with the relevant flat owner.
Look at the leases for the flats and any deeds of variation. Before granting consent, the freeholder should also have been satisfied that the flat owner had obtained necessary planning, listed building or building control consents and had considered any Party Wall Act issues.
If the structure was built on a communal garden, the freeholder may have charged the flat owner a premium.
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If you have a question for Fiona McNulty, email firstname.lastname@example.org. We regret that questions cannot be answered individually.
Fiona is a partner in the residential real estate team at Thring LLP (www.thrings.com).
These answers can only be a very brief commentary on the issues raised and should not be relied on as legal advice. No liability is accepted for such reliance. If you have similar issues, you should obtain advice from a solicitor.