A loft conversion in Holborn begins with a question that barely arises on a suburban house: who owns the roof. Most homes here are flats within mansion blocks and converted buildings, and in a typical lease the demise stops at the ceiling of the top-floor flat. The roof structure, the void above it and the airspace over the building are usually retained by the freeholder. That makes the first exercise a title one, not a design one. Until the demise is read and the freeholder's position on the airspace is known, a beautifully drawn roof scheme is academic, because the space it occupies may not be yours to build into.
Where the roof space is retained, taking it in generally requires an airspace lease or a variation to the existing lease, freeholder consent and a Licence to Alter, each of which can shape the project before the council is ever approached. Managing agents in older mansion blocks often set their own conditions on method, access through common parts and the hours work may proceed, and a surveyor may be appointed at the leaseholder's cost to approve the structural proposals. We advise settling this non-council audience at the very outset, so effort is not spent designing a scheme the lease and the freeholder will not permit.
Adding an occupied level changes the fire strategy of the whole building, and in Holborn's older mixed-use and converted stock that is rarely straightforward. Many of these buildings rely on a single common stair, sometimes serving residential floors above commercial or office use below, and Building Regulations expect a protected route from the new level to a final exit. That can mean upgrading fire doors, linings and compartmentation on floors well beneath the new work, and the escape strategy for the added storey has to be reconciled with the existing means of escape for every other flat on the stair, not designed in isolation.
Structurally, a roof over a converted or mansion-block flat was never built to carry habitable rooms. New joists, beams at the ridge and along the party-wall lines, and steel where spans are long, all have to be threaded into a building that must stay watertight and occupied around the work. In older construction the existing structure and its load paths cannot be taken on trust, so an opening-up survey and a structural engineer's assessment come early. The party walls and parapets shared with neighbouring buildings are load-bearing to the scheme and legally significant, which is where the Party Wall etc. Act 1996 enters the programme.
Services are the quiet complication of any top-floor addition. A new bathroom or kitchen at roof level has to drain back to the building's existing soil stacks, which may run in constrained shared risers not sized for extra connections, and extract and any plant have to be routed without breaching fire compartmentation or the freeholder's controls over the roof. In a converted building the risers were often improvised during an earlier conversion, so their true capacity and route need to be established rather than assumed. Getting the drainage falls and riser strategy resolved on the drawings avoids the expensive discovery that the services cannot physically reach the new floor.
Only once ownership, fire, structure and services are understood does the planning route come into focus, and in Holborn that route runs through one of two authorities. Depending on the address, Camden or the City of London determines the application, and the correct body must be confirmed street by street. Where the property sits within a conservation area the roofscape is assessed as a visible elevation, and any dormer or added storey is weighed against how it reads from surrounding streets. Because flats have no permitted development rights for roof work, we plan for a full application from the start, with freeholder consent secured alongside it.
