The case for change. How planning permission works in London - and how to change a home without losing what made it special
People are drawn to a house, or a street, or a neighbourhood for its character. The proportions of the windows, the rhythm of the terrace, the mature trees, the quiet consistency of a conservation area - these are the qualities that make a place feel worth living in, and they are usually part of why someone bought there in the first place.
Then comes the wish to change. A home needs to work differently than it did a century ago, and adapting it is entirely reasonable. But there is a quiet risk in it: that the changes made in pursuit of a better home chip away at the very character that made the place attractive to begin with. A poorly judged extension, an unsympathetic alteration, a loss of the features that gave the house its quality - these can leave a home that works better in some narrow sense but has lost something it will not get back.
This is what the planning system, at its best, exists to hold on to. It is not simply an obstacle between a design and its realisation, though it can feel that way. It is the mechanism by which a city tries to keep the qualities that make its places worth living in - and understanding it is really about understanding what is worth keeping, and how to change a building without diminishing it.
Much of a good outcome is decided before an application is ever submitted: in the way the proposal is shaped, and in the strength of the case made for it. The rest of this is about how that process works, and how to give a project the best chance of succeeding - not just in gaining permission, but in making a change genuinely worth making.
What needs permission and what does not
Not every project requires planning permission. Many smaller works - certain extensions, most loft conversions, a range of internal alterations - can be carried out under permitted development rights, which allow the work without a formal planning application provided it stays within defined limits.
Permitted development rights are restricted or removed in some situations, particularly in conservation areas, where an Article 4 direction applies, or where the property is a flat or a listed building. The detail matters, and it differs by project type: what applies to a loft conversion is not the same as what applies to a rear extension. Those specifics are covered in separate articles on loft conversions, conservation areas, and extending a Victorian terrace. This piece is about what happens when a full application is needed - the process itself.
What a planning application involves
A householder planning application - the type used for most home extensions and alterations - is submitted to your local planning authority, which in North London means the borough: Haringey, Camden, Islington, Hackney, Barnet or a neighbour, depending on where you live.
The application sets out the proposal in drawings - existing and proposed plans, elevations and sections - usually with a design and access statement explaining the thinking and how the scheme responds to local policy and context. Where the setting calls for it, further material may be needed: a heritage statement in a conservation area, daylight and sunlight information where neighbours might be affected, arboricultural information where trees are involved. The right supporting material, pitched at the right level for the project, is part of what makes an application persuasive rather than merely complete.
Once submitted, the application is validated by the authority, published, and opened to consultation - neighbours and interested parties are notified and can comment. A case officer is assigned to assess it against national policy, the borough's local plan, and any supplementary guidance that applies.
Timescales - and why they slip
The statutory determination period for a householder application is eight weeks. In principle a decision arrives within that window. In practice, many London boroughs take longer, because the volume of applications they handle outstrips the resources available to assess them.
It is worth planning for this from the outset. An eight-week period can become twelve or more, and a project programme built on the statutory minimum will slip. Building the realistic timescale into your thinking early - rather than assuming the best case - avoids a good deal of frustration later, and it affects decisions such as when to approach contractors and when to begin the party wall process.
The value of talking to the planners first
Most London boroughs offer pre-application advice - a paid service in which a planning officer reviews an outline proposal and gives an informed view before a formal application is made. On any project that is not entirely straightforward, it is time and money well spent.
Its real value is that it brings the planners into the process early. It engages the authority in the thinking, surfaces concerns while the design can still respond to them, and often reveals something that had been overlooked - a policy consideration, a local sensitivity, a constraint that would have emerged later at greater cost. Good design benefits from many experienced eyes on the problem, and a case officer's early view is among the most useful you can have.
The balance between ambition and what is achievable
There is almost always a tension between what a client would like and what a site can realistically carry through planning. Part of the work is finding the right point between the two.
The closer a proposal sits to what is genuinely achievable, the more constructive the feedback from the planners tends to be. A scheme pitched a little beyond what policy comfortably allows can still be worthwhile - it tests the limits and draws out useful guidance on where those limits lie. But pushed too far, it risks antagonising the officer and hardening their position. Pitched too cautiously, it can leave real potential unexplored, and the client with less than the site could have given them. Judging that balance - ambitious enough to explore what is possible, grounded enough to keep the planners constructive - is one of the more skilled parts of the process, and it comes from experience of how these judgements actually play out.
When to bring in a planning or heritage consultant
Most householder applications do not need a planning consultant. On a listed building, or where something out of the ordinary is proposed in a conservation area, one can make the difference between consent and refusal.
What matters is that the case is argued from a single, coherent position. Where planning and heritage are treated as two separate voices - a planning consultant making one argument and a heritage consultant making another - the case for change can end up weaker than the sum of its parts, because the two are not working from the same ground. A planning consultant who can also argue from a heritage standpoint, or a team genuinely working as one, makes a far stronger case. The argument for change is most persuasive when it comes from one place.
Do you need an architect who knows the local council?
It is a common and reasonable belief that the best person to handle your application is an architect who knows your local authority. It feels intuitive - a familiar face, an established relationship, inside knowledge of how the borough thinks.
In practice, it matters less than people expect. Case officers change from one application to the next, so the familiar face is rarely the one assessing your scheme. Planning policy and law shift over time, so yesterday's knowledge of a borough is not a reliable guide to today's decisions. What actually determines the outcome is the quality of the proposal and the strength of the case made for it, assessed against the policy that applies now.
There is a real strength in working across many boroughs rather than one. It requires you to approach every project from first principles - reading the specific site, the specific policy context, and the current guidance freshly each time, rather than leaning on assumptions carried over from the last application. Local knowledge that genuinely matters, such as the character of a particular conservation area or a specific local plan policy, is researched properly for every project as a matter of course. It is captured through diligence rather than assumed through familiarity - which is the more reliable way to capture it, because it cannot go out of date.
Making a change worth making
The planning process rewards preparation. A proposal shaped with a clear understanding of policy, tested early with the planners, pitched thoughtfully between ambition and achievability, and supported by the right material and the right expertise, has a far better chance than one submitted hopefully and adjusted later.
But the deeper aim is not simply to gain permission. It is to make a change that leaves the home better without costing it the character that drew you to it in the first place. Understanding the planning system is part of understanding what is worth keeping - and the best changes are the ones that respect what is already there while allowing the house to work for the way you live now.
If you are planning a project in London and would like to understand what the planning process might involve for your property, get in touch here: https://www.pierremare.com/contact