In South Hampstead the first loft question is not what shape the dormer takes but who owns the roof. Much of the local stock is red-brick mansion blocks and large houses converted into flats, and in that stock the roof void and the airspace above it frequently sit outside any individual flat's demise — retained by the freeholder, or held as common parts that every leaseholder contributes to maintaining. A top-floor leaseholder can therefore be contemplating a roof they have no legal right to build into, whatever the planning position turns out to be. So the sequence is deliberately inverted here. We read the lease and the title plan, establish whether the void is demised, and establish whether the freeholder will sell or licence the airspace, before a measured survey is commissioned or a single layout is drawn. Where the building is a whole house in single ownership the question falls away — but the same street can hold both, so the address, not the area, decides.
Where the property is a single-family house, the conversion runs the familiar Camden householder route and the controlling question becomes visibility. The conservation-area appraisal adopted in February 2011 is used in assessing applications in the designated area, and Camden's guidance treats roof alterations as sensitive fabric rather than as a technical afterthought. Because the designation does not necessarily reach every address, we confirm it for the exact property first. Permitted development is where owners most often go wrong: those rights are commonly restricted on conservation-area land, and Camden's Article 4 material adds a further layer over fronts and street-facing sides. Rather than build a design on an assumption that a case officer can contradict at validation, we establish what the roof is actually allowed to carry — and where rights may genuinely survive, we recommend confirming them formally with a lawful development certificate rather than relying on them. Head height is the other early number: the clear height under the existing roof structure, less the new floor build-up and the insulation zone, is what decides whether a usable room and a compliant stair can be won at all, and that is a survey question, not a hopeful one.
Article 4 has two practical consequences for a loft here. First, a change to a roof plane that reads from the street, or to a visible flank, cannot be treated as permitted development on the assumption that a rear-facing equivalent would be — the described controls reach the fronts and street-facing sides of single-family houses and converted flats. Second, if the scheme carries photovoltaic or solar thermal panels onto a front or street-facing side, that equipment is itself within the Article 4 description, so a roof that is being reworked anyway is exactly when the panel question should be settled. Where the roof is a rear-facing slope concealed by the building's own bulk, the planning conversation is usually quieter — but it still runs through the conservation-area assessment, and quieter is not the same as unregulated. The corollary is a design instruction rather than an obstacle: establish the visible planes first, keep the new work off them where the building will allow it, and where it cannot be kept off them, submit existing and proposed roof plans and elevations, street-level photographs and a materials note as a matter of course rather than as a response to a late request from the case officer.
Structure in a converted building is rarely as built. South Hampstead's converted flats often contain inherited alterations: an earlier conversion may already have moved walls, cut joists, altered fire separation or changed how load reaches the ground, and none of it is necessarily recorded anywhere you can find it. A loft conversion loads the existing structure — new floor beams, a reinforced or rebuilt roof, a stair opening cut through the top-floor ceiling — and those loads have to arrive somewhere that can take them. The survey here is therefore partly forensic. We open up where we are permitted to, trace the load path down through the demises below, and involve a structural engineer early, because in a building of several owners the discovery that a beam needs to bear on a wall inside somebody else's flat is a project-changing fact, not a detail to be resolved on site.
Adding a habitable storey changes the fire strategy, and in a subdivided building it changes it for people who are not your client. Building regulations cover structure, fire safety, insulation, ventilation, drainage, stairs and waterproofing, and a new top storey typically brings a protected escape route, fire-resisting construction around the stair and interlinked alarms into scope. Where the building contains separate demises, fire separation and fire stopping between flats and into common parts is precisely the evidence a freeholder and a managing agent will demand, and a thin pack is where these projects stall. Sound is the twin of it: the new floor sits on somebody else's ceiling, so an acoustic build-up between demises has to be designed rather than promised — and that build-up consumes head height, which is why it belongs in the feasibility rather than in the final technical drawings. Means of escape from the new storey is the point on which these schemes most often turn, because the escape route does not stop at the front door of the flat; in a converted or purpose-built building it continues through the common stair, and that is the freeholder's asset, not the leaseholder's.
The last trap is services. A shower room or bathroom in a new roof storey needs soil, waste and ventilation, and in a converted building those routes rarely exist where the plan wants them. A new stack, a riser dropped through the storeys below, an extract terminal or a flue can each end up as a penetration on an external elevation, so an internal decision becomes an external planning problem on a conservation-area face — or an Article 4 one if it lands on a front or street-facing side. We fix the service routes and riser strategy before layouts are frozen. From there the route is coordinated: lease and demise check, measured survey, structural and fire strategy, the Camden application, the freeholder's Licence to Alter pack with method information and common-part protection, then the building regulations drawings and any party wall notices where beams bear into a party structure. We do not promise approval.
