House Extensions and Renovation in Colindale NW9 — a District Built by a Plan
Every other part of north west London was built by landowners, speculators and the railway, then protected afterwards. Colindale was built by a planning document.
The London Plan identified it as an Opportunity Area, Barnet adopted an Area Action Plan in 2010 to deliver it, and the current Local Plan carries the Colindale Growth Area with the same boundary. The target was a minimum of 12,500 new homes. Barnet’s own estimate is that around 35,000 people will live here once the schemes complete — in an area that a generation ago was largely an aerodrome, a police training college and a few streets of inter-war semis.
So the housing splits three ways. New apartments, thousands of them, at Beaufort Park on the old RAF Hendon site, at Colindale Gardens and across the rebuilt Grahame Park. The 1920s and 1930s semi-detached and terraced houses that were here first. And the 1970s system-built stock, part of it now replaced.
Design And Build works across all three. We employ everyone the job needs — designers, engineers, party wall surveyors, trades — and a single contract covers all of them.
House Extensions and Builders in NW9: Why Most Colindale Homes Have No Conservation Area
The aerodrome, the Opportunity Area and 12,500 homes
Hendon Aerodrome closed to flying and the land came forward for housing. The Peel Centre, the Metropolitan Police training college, went the same way. Both the Greater London Authority and Barnet took the view that the area needed to change, and Colindale was designated an Opportunity Area in the London Plan with a minimum housing target of 12,500 homes.
The Barnet Local Plan now sets the boundary of the Colindale Growth Area as the same as the Opportunity Area. Which means the policy framework here is about delivering new development rather than restraining change to what already exists — the opposite starting point from almost anywhere else in the region.
What that leaves you: no designation, no Article 4
There is no conservation area over the new development, none over the inter-war streets, and no Article 4 Direction. A homeowner in Colindale is in the most permissive planning position available anywhere in north west London, and considerably freer than a neighbour two miles away in Golders Green or Mill Hill.
If you own a house, that puts a good deal within reach automatically — permitted development regularly covers building out at the back, altering the roof and putting up a garden structure with no application needed — and where a scheme qualifies a lawful development certificate records the fact for a future sale. For a flat it means something quite different, because the constraint in a managed block was never the council in the first place.
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House Extensions on a Colindale 1930s Semi
The rear extension, and what the ground allows
The inter-war houses here were built with generous back gardens and a kitchen at the far end of the plan. Taking the rear wall out over the whole span is the usual scheme here, and the one that alters how a family lives more than any other — two or three cramped spaces become one, with the garden on the far side of the glass.
Ground conditions decide how it is built. Much of Colindale sits on London clay, which shrinks and swells with the seasons, and mature trees near a proposed foundation make that movement worse. Foundation depth here is worked out for the plot rather than taken from a standard detail, and our structural engineers settle it at survey.
Subsidence on clay, and cavity walls that have failed
Two defects recur in this stock and both affect what a project should cost. Subsidence in 1930s semi-detached houses on shrinkable clay, usually showing as diagonal cracking around openings and worsening in dry summers. And failed wall ties in cavity construction of the same period, where corroding ties push the outer leaf outward and produce horizontal cracking at regular intervals up the wall.
Neither is a reason not to proceed. Both are reasons to survey properly first, because an extension built onto a house with an unresolved movement problem inherits the problem and hides it.
What permitted development still covers here
On an undesignated street the national rules apply in full: depth and height limits for a single-storey rear extension, more depth for a detached or semi-detached house than for a terrace, and separate allowances for outbuildings and roof alterations.
The one check worth making first is how much of that allowance a previous owner has already used, because the calculation starts from the dwelling as first constructed, not from whatever stood there on the day you completed. On a street where a good many houses were extended in the 1980s, that answer changes the route rather than the design.
Home Renovation on the Older Colindale Streets
Renovating a house already altered twice
The typical inter-war house in NW9 has been improved in stages by several owners: a rear addition at some point, a converted garage, a kitchen refitted twice, wiring extended wherever there was a route, and insulation added in patches. What a full renovation confronts is the accumulated decisions rather than a building in poor repair.
Taking those layers out first is what makes the rest work. Services renewed end to end, the fabric brought up to standard by methods cavity-era construction will tolerate, and the plan rearranged for the household living there now. Interior design belongs in that while partitions can still move.
The Grahame Park estate and the 1970s stock
Grahame Park was built on former aerodrome land in the 1970s and is Barnet’s largest housing estate. Notting Hill Genesis and the council are rebuilding it in phases, with a compulsory purchase order made in May 2022 and completion running toward the 2030s. Where the original stock survives it is concrete and system-built, which behaves differently from masonry and needs surveying on its own terms.
Work in a part-regenerated estate also has practical complications that have nothing to do with the building: phased demolition nearby, changing access routes, and a site that is under construction around you. We plan the logistics alongside the build because in this part of NW9 they frequently decide whether a programme holds.
Flat Refurbishment in a Managed Colindale Block
What Beaufort Park and Colindale Gardens set as the terms
Beaufort Park alone runs to more than three thousand apartments with a permanent on-site management team; Colindale Gardens and the rebuilt Grahame Park add thousands more. Refurbishing inside one of these blocks means working to the building’s rules rather than your own — when you can get in, which lift you can use and when, how the common parts are protected, what hours are permitted and where the waste leaves.
Good work happens in these buildings all the time. What it needs is a programme written around the block from day one — because a contractor who finds out about the lift booking system after starting has already lost days he will not get back.
Your managing agent, and asking them first
This is the single most useful thing a Colindale flat owner can do before anything else. Contact the managing agent and ask what the block requires for alterations — what has to be approved, by whom, what documents they want, whether contractors need to be approved or insured to a particular level, and how long they take to respond.
On a large managed development that process is established and repeatable, which is good news: it means there is a known route rather than a negotiation. It is also the step most often left until the design is finished, which is when it costs time.
Your lease, and what it lets you move
The lease decides the limits. Anything structural, anything affecting services shared with other flats, and often anything altering floor finishes will need the freeholder’s formal consent, usually by licence to alter. Permitted development was never granted to flats to begin with, which means any change to the outside is a planning matter wherever your block happens to be.
Sound between dwellings is worth raising early. Part E of the Building Regulations governs separating floors and walls, and in a modern block the floor build-up is frequently specified in the lease as well. Changing it is not always permitted, and finding out after the flooring is ordered is an expensive way to learn.
New-build warranties, and what alterations do to them
A large share of Colindale housing is recent enough to still carry a new-home warranty. Those warranties cover defects in the original construction, and they generally set conditions about alterations — what may be changed, when, and whether cover continues on the affected elements afterwards.
Terms differ by provider and by policy, so the answer is in your own documents rather than in general advice. We raise it at the first visit, because on a flat only a few years old it can change what is worth doing now and what is better left until the cover has run its course.
Colindale Builders and Construction Contractors for NW9
What one firm covers
The conventional route is separate appointments: someone to design it, an engineer for the calculations, a surveyor for any neighbour notices and a builder for the work. It functions, and coordinating it falls to the client.
Inside one business it works differently. Our architects and engineers develop the scheme together. Where an application is needed we prepare and pursue it with Barnet. Our party wall surveyors deal with the Party Wall etc. Act 1996 on a semi-detached house, where most structural work engages it. The construction is handled by our own workforce, to one schedule.
Who has to agree, and in what order
In Colindale the answer depends entirely on what you own. On an inter-war street it may be nobody at all, or Barnet alone. In a managed block it is the managing agent and the freeholder, and the council only where the work is external. On the estate it can be all of them, plus whatever the regeneration programme requires nearby.
We establish the full list at the first visit and pursue them together. Consents chased in parallel take weeks; consents chased in sequence take considerably longer, and the order is rarely obvious from the outside.
Area We Cover
Price Your Colindale Extension or Refurbishment
Tell us the property and roughly what you want done. What you get back is a plain account of what actually controls the job — the planning position on a house, the lease and management position on a flat, what permitted development remains, and what the ground or the structure will take — then write the job up in itemised form, attach a fixed figure to it, and show whatever contingency an older building warrants as a separate line rather than folding it into the rate.
We cover Colindale and the surrounding NW9 area — Beaufort Park, Colindale Gardens, Grahame Park, the Edgware Road corridor and the streets towards Hendon and Burnt Oak — and we work equally across Mill Hill, Golders Green, Willesden and north west London more broadly.
The survey is free. If you own a flat, speak to your managing agent first — then call us.
