Who owns the roof space, and how to acquire it
The question is answered by the lease and by the freehold title, not by common sense or by who has been storing boxes up there. In the standard arrangement for a converted house, the freeholder owns the building and grants long leases of each flat, and the demise of the top-floor flat is defined by reference to its internal surfaces — floors, walls and, critically, the ceiling. The roof structure and the void above it are retained by the freeholder, along with the external walls, the foundations and the common parts. That means the loft is not yours to convert, and building into it without acquiring it is a trespass as well as a breach of covenant, regardless of any planning permission obtained. Where the roof space is not demised, there are two routes to acquiring it and they are often combined. A deed of variation extends the demise of your lease to include the void, and a lease extension — whether negotiated by agreement or claimed under the statutory route where you qualify — is frequently used as the moment to renegotiate the demise at the same time, because both are valuation exercises and doing them together avoids paying twice for the same uplift. In either case a premium is payable, and it reflects a share of the value the conversion will create rather than the value of an empty void, so it is negotiated with a valuer rather than agreed on a rule of thumb. Where the leaseholders own the freehold collectively through a company, the decision belongs to that company and therefore to your neighbours, which changes the negotiation from a commercial one to a domestic one — usually easier, but requiring the company’s formal consent properly minuted rather than an agreement over the garden fence. The order that saves money is: check the lease, establish the freehold position, open the negotiation, and only then commission design work. Drawings prepared before the demise is settled are frequently redrawn.
