House Extensions, Renovation and Builders Across North West London — Five Levels of Planning Control in One Region
North west London runs from Camden Town out to Mill Hill, and somewhere along that line almost every form of planning control in England applies to somebody’s house.
At one end there are streets where nothing applies at all and a rear extension needs no permission. At the other there are houses where the council has withdrawn permitted development, a private trust vets the colour of your front door, and a national policy test measures your proposal against the building as it stood in 1948. Between those two extremes sit four boroughs, dozens of conservation areas, and a great many homeowners who assume their position is the same as their neighbour’s.
Which is the single most useful thing to establish before anything else. Not what you want to build — what governs the address. Design And Build works across the whole region, and the architects, engineers, party wall surveyors and trades are all employed here directly, on one contract.
The Five Positions a North West London House Can Be In
Nothing applies: most of Willesden, Acton and the Golders Green streets
A large share of north west London sits outside every designation. The inter-war streets around Golders Green and Temple Fortune, most of Willesden away from the conservation areas, the terraces of Harlesden behind the high street, and the semi-detached roads out towards Mill Hill Broadway.
On these addresses permitted development does most of the work. Rear extensions, loft conversions and outbuildings frequently proceed with no application at all. What does need establishing at the outset is how much of the entitlement earlier owners have used, since the calculation runs from the dwelling as first constructed. Where a scheme qualifies, a lawful development certificate records it for whoever buys the property next.
Conservation area only
Designation by itself governs the public face of a building. What a passer-by can see — the frontage, any roof in view from the pavement, walls and railings, the materials used — is examined closely, while work at the back and inside draws far less attention. Much of Camden sits here, as does the Golders Green town centre designation — which, despite its name, is a retail area of shopping parades with only a few hundred residents living above them.
The practical effect is that the back of the house is where the project happens and the front is a separate, careful conversation. It is a workable position, and a great deal is achievable within it.
Conservation area with an Article 4 direction
An Article 4 Direction withdraws permitted development rights that would otherwise apply automatically, so work that needs nobody’s permission a street away becomes a full application. The pattern varies sharply by council. Brent applies directions across every one of its residential conservation areas, and moved several boundaries in May 2024 — which caught streets in Willesden that had been outside designation for thirty years. Camden operates directions on the Hampstead side of the borough.
Where a direction applies, the practical questions become which classes of development it removes and whether it reached your address specifically, since some councils apply them property by property rather than area-wide.
A private trust or estate on top of the council
Two parts of north west London add a further layer that has nothing to do with planning law. In Hampstead Garden Suburb the Trust holds separate legal powers and nothing changes on the outside of a house or in its garden without the Trust signing it off — an extension, a dormer, new windows, a repaint, a driveway, a wall, even a hedge. That binds the freeholder, not merely anyone holding a lease.
In St John’s Wood a large share of the district is still held on lease from a single charitable freeholder, whose licence to alter is needed for structural work and anything affecting the demise. In both cases the council’s permission and the estate’s consent are separate, and one does not imply the other. A scheme that satisfies the planners and not the estate has not got very far.
Green belt, where a different test applies entirely
Parts of Mill Hill fall within the Metropolitan Green Belt, where national policy replaces the usual questions with one of its own: whether a proposal amounts to a disproportionate addition over and above the size of the original building.
The word “original” is defined rather than descriptive: whatever stood there on 1 July 1948, or the building as first erected if it came later. Anything added in the intervening decades is counted in, whoever added it and however long before you arrived. A property extended twice may have very little allowance remaining, however modest the new proposal looks. It is the one position where establishing the history matters more than designing the scheme.
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House Extensions and Loft Conversions: What Each Position Allows
Where permitted development still does the work
On an undesignated street the standard projects run without an application: a rear extension within the depth and height limits, a hip-to-gable loft conversion with a rear dormer, a garden building within the permitted size. The design conversation is about what the house needs and what the ground will take, rather than what an officer will accept.
Our structural engineers settle foundation depth and the structural openings at survey, because on London clay near mature trees that is a design question rather than a standard detail.
Where the application is the route
Inside a designation, or where a direction has removed the rights, the project becomes a submission with a heritage statement attached. That changes the timescale and it changes the design process, since the scheme has to be argued rather than simply built.
Our architects read the relevant character appraisal before drawing, because councils in this region are unusually specific about what they consider appropriate street by street. We prepare and argue the application ourselves rather than handing over drawings for somebody else to defend.
Where a second consent decides it
Where a trust, an estate or a freeholder is involved, the sequencing is most of the project management. Consents that run in parallel take weeks; consents that run one after another take seasons, and the order is not always obvious from the outside.
We establish the full list of who has to agree at the first visit and pursue them together — the council application, the estate or trust consent, the freeholder’s licence to alter where a lease applies, and party wall notices under the Party Wall etc. Act 1996, which our surveyors serve.
Home Renovation and Flat Refurbishment by Borough
Camden: Camden Town, Kentish Town, Hampstead
Camden holds around forty conservation areas covering roughly half the borough, and requires a heritage statement with every application in a designated area. Camden Town is largely flats above commercial frontage; Kentish Town was built plot by plot so adjoining houses differ in age and construction; Hampstead carries Article 4 directions and some of the most closely watched roofscape in the borough. Whole-house renovation and leasehold refurbishment are the common projects across all three.
Brent: Willesden, Harlesden, Kilburn
Brent has twenty-two conservation areas and applies an Article 4 direction to every residential one. Willesden saw its boundaries extended in May 2024; Harlesden has its designation over the town centre rather than the houses behind it; Kilburn straddles three planning authorities along the High Road. The stock is late-Victorian and Edwardian terraces, much of it divided into flats, so renovation and flat refurbishment dominate.
Barnet: Mill Hill, Golders Green, Colindale
Barnet is the suburban end of the region — inter-war semis and detached houses on real plots, with green belt at Mill Hill and the Hampstead Garden Suburb Trust at Golders Green. Colindale is different again, dominated by newer development. These are houses with side access and deep gardens, so extensions and loft conversions are the standard work rather than the exception.
Westminster: St John’s Wood
Since 31 July 2016 there has been no automatic route to a basement anywhere in Westminster, the council having removed those rights across the whole city. St John’s Wood adds the estate freeholder to that, and its housing runs from the original garden-suburb villas to red-brick mansion blocks. Whole-property refurbishment and flat refurbishment are the work here; extending is rare.
North West London Builders and Construction Contractors
The conventional arrangement is four or five separate appointments, coordinated by whoever owns the house. It functions, and in a region where the first question is which of five positions your address occupies, it puts a considerable amount of work on the client.
We hold all of it. The design and the engineering are developed together in house, so nothing is drawn that the structure or the ground will not take. Any application is ours to prepare and pursue with the relevant council. Anything an estate or a freeholder has to approve is pursued at the same time, not once the council has finished. Neighbour notices are drafted and served by our own surveyors, who work out first who actually holds the right to receive one. Interior design runs with the layout rather than following it. The building itself is done by people on our payroll, to a single schedule.
You get a scope set out line by line, a price fixed against it, and the allowance for what an older building may be hiding shown openly rather than buried in a rate. At completion: building control sign-off, the certificate and warranty pack, snagging worked to nothing, and a written guarantee.
Area We Cover
Find Your Position Before You Design
The survey costs nothing and it answers the question that governs everything after it. Which council decides your application, whether a conservation area or an Article 4 direction reaches your address, whether a trust or an estate has to consent as well, whether green belt policy applies, and how much of the permitted development allowance a previous owner already used.
Once that is settled the rest follows: what is achievable, what route it takes, how long it should take and what it should cost. Before it is settled, everything is guesswork.
Send us the address and we will start there.
