Guide · 20 October 2026

Building costs and house prices in Camden

Most people in Camden don’t live in a house. The Census 2021 accommodation-type table (TS044, via Nomis) counted 92,759 households in the borough, and 56.2% of them lived in a purpose-built block of flats, against 40.3% across London. Another 26.2% lived in part of a converted or shared house, the highest share of any London borough. Just 13.4% had a whole house to themselves: 8.1% in a terrace, 3.6% in a semi and 1.7% in a detached house. Only the City of London, Westminster and Tower Hamlets had a smaller share of households in houses.

That changes the usual extension conversation. For a lot of Camden owners the question isn’t how far back they can build, but whether a garden flat can take a rear room, whether a top flat can go up into the roof, or whether two flats in a Victorian house can work better as one. And for the minority who own a whole terrace in Kentish Town, Camden Town or Belsize Park, the big decisions are usually about the roof and, much more carefully than elsewhere, about digging down.

Camden house prices in July 2026

The latest UK House Price Index from HM Land Registry and the ONS covers July 2026 (provisional), and puts Camden’s average price at £815,159. Only Kensington and Chelsea and Westminster are higher. The average is 10.1% lower than in July 2025, against a 3.3% fall for London as a whole, which makes it the fifth-steepest annual drop of London’s 33 local authority areas. It is also 2.3% down on June. July 2025 was the borough’s highest month on record in the HPI, at £907,073, so prices have now given back a full year of gains. First-time buyers paid £711,980 on average.

Two things are worth knowing before you lean on these numbers. First, Camden is a small market: the HPI recorded 81 sales in the borough in May 2026, the latest month with a count, so a handful of expensive or cheap sales can move the average noticeably. Second, with so few detached and semi-detached houses in the borough, the averages for those types rest on very few sales and can swing a long way, so treat them with real caution. All figures come from the HPI full data file for July 2026; they are borough-wide averages, they will be revised in later releases, and they can’t value any particular home.

Moving up or building on?

On July’s averages, the step from a flat to a terraced house in Camden was about £883,000, more than the whole price of an average Camden flat. Going from a terrace to a semi added roughly another £563,000. Stamp duty, legal fees, surveys and removals come on top of those gaps, and at Camden prices stamp duty alone is a large sum.

Nobody publishes building costs for Camden on its own, so the figures below are national ballparks. Checkatrade’s house extension cost guide, updated in June 2026 and checked by estimators who are members of RICS and the CIOB, gives these UK figures:

• £1,800–£3,000 per m² for a finished single-storey extension, excluding VAT, so £40,000–£56,000 for 20m² and £60,000–£84,000 for 30m²
• £108,000–£180,000 for a 60m² two-storey extension
• £50,000–£95,000 for a 30m² loft conversion
• £100,000–£160,000 for a 40m² basement, with some projects going higher

Because the traditional London roof extension is a mansard, it’s also worth noting that Checkatrade’s loft conversion guide (March 2026) puts a 30m² mansard at £50,000–£80,000, around £65,000 on average, and says mansards tend to be the most expensive kind of loft conversion because of the structural work involved. Both guides say that prices in London and the South East usually come in above these national figures, so treat them as a floor rather than a quote.

Even with a London premium, a mansard or a rear extension costs a small fraction of the £883,000 jump from a flat to a terrace. That doesn’t mean building always pays: the work adds space, not a new property type, and no one can promise what it will add when you sell. Use these numbers to test a budget, not to forecast a profit.

If you own a flat

Householder permitted development rights belong to houses. Camden’s own Home Improvements planning guidance spells out that they generally don’t apply to flats or to properties converted into flats, so with more than eight in ten Camden households living in some kind of flat, most extensions here start with a planning application. If you are a leaseholder, you will usually need the freeholder’s consent as well, so check your lease before you pay for drawings. A rear extension to a garden flat also has to answer to the neighbours above, and the council’s guidance specifically mentions light spilling up to flats overhead.

Permitted development for houses

For houses, the national rules on the Planning Portal still apply where they haven’t been taken away. A single-storey rear extension can usually go 3 metres beyond the original back wall of a terrace or semi, or 4 metres for a detached house, with the prior approval route allowing 6 and 8 metres. The loft conversion guidance allows 40 cubic metres of extra roof space on a terrace and 50 on other houses, with nothing projecting beyond the front roof slope. In practice these rights go less far in Camden than almost anywhere, because about half the borough is a conservation area (where side extensions, rear extensions of more than one storey and roof extensions need permission), thousands of buildings are listed, and basements have been taken out of permitted development altogether.

What Camden looks for in an extension

When you do need permission, the council judges the scheme against its Local Plan, adopted on 3 July 2017, and its January 2021 Camden Planning Guidance documents. A new Local Plan was submitted for examination on 3 October 2025, but until it is adopted the 2017 plan is the one that applies. The Home Improvements guidance is the most useful for householders:

• Rear extensions should be subordinate to the house in footprint, scale and detailing, respect the pattern of neighbouring extensions, leave a reasonably sized garden, and pass the 45-degree and 25-degree daylight tests in the council’s Amenity guidance or show compliance through a daylight study.
• Mansards are described as the most common roof extension in the borough, and a traditional design is preferred on Georgian and Victorian buildings: a lower slope of roughly 60 to 70 degrees set behind the parapet, with the cornice, parapet and chimney stacks kept. The guidance says that if neighbours in your terrace already have a traditional mansard, a similar one is likely to be acceptable.
• Dormers should be subordinate to the roof slope and evenly spaced from the ridge, eaves and side parapets. The guidance also drops the old hard line against any extension on an unbroken roofline, and gives weight to older extensions nearby, including ones built under permitted development.

Even where work is permitted development, the council strongly recommends a Lawful Development Certificate, and extensions, lofts and basements all need building regulations approval. Camden’s planning permission checker is a sensible first stop.

Conservation areas, listed buildings and Article 4 directions

Camden Council’s conservation areas page says there are 40 conservation areas covering about half the borough, each with an appraisal and management strategy that describes what the council wants to protect. It asks for a heritage statement with any application in one. The borough also has more than 5,600 listed buildings, from St Pancras Old Church to the Alexandra Road Estate, and listed building consent covers the interior as well as the outside.

On top of that, several conservation areas have Article 4 directions that remove permitted development rights from houses and flats to protect historic features. Updated directions were adopted on 9 June 2026 for Belsize, Fitzjohns/Netherhall, Hampstead (including Frognal Way), Redington and Frognal, and South Hampstead (formerly Swiss Cottage). Older directions cover parts of Primrose Hill (1983) and South Hill Park (1989). The Belsize fact sheet shows the kind of thing they catch: changing front windows and doors, altering the front of a house or the front roof slope, painting the front, and changing front walls, gates and railings. It notes that controls on rear elevations haven’t changed, and that there is currently no fee for applications needed only because of the direction. Check the map for your own address before ordering windows, never mind planning a roof.

Basements: planning permission every time

Since 1 June 2017, a borough-wide Article 4 direction has meant that every basement or lightwell excavation in Camden needs planning permission. The Basements planning guidance (January 2021) then sets out how Local Plan Policy A5 is applied. In short, a new basement should:

• be no more than one storey deep, which the council takes to mean an excavation of roughly 3 to 4 metres, and not go under an existing basement;
• cover no more than 50% of each garden (front, back and side are counted separately);
• be less than 1.5 times the footprint of the house;
• extend into the garden no further than half the depth of the house, measured from the main rear wall, and no further than half the depth of the garden;
• avoid habitable rooms in areas prone to flooding.

Every scheme needs a Basement Impact Assessment covering ground movement, groundwater and drainage, and the guidance says most will be independently checked on the council’s behalf at the applicant’s expense. Some also need a basement construction plan secured by a legal agreement. Add those fees, and the time they take, to the Checkatrade figures above before you compare a basement with a mansard. The council’s basements page has the forms and further detail.

Party walls

Terraces and converted houses mean shared walls almost everywhere in Camden, and basements bring in the excavation rules too. Steels into a party wall, a new wall on the boundary, or digging within 3 or 6 metres of a neighbour’s foundations (depending on depth) can all need notice under the Party Wall etc. Act 1996. GOV.UK’s guidance explains the notices, the time limits and what happens if a neighbour dissents, when surveyors agree an award setting out how the work will be done. In a house split into flats, the neighbours may be above and below you as well as next door, so talk to them early.

Checking a builder

Be wary of anyone who knocks on the door because they’ve spotted scaffolding nearby, wants a large cash deposit, or gives a single round figure with no breakdown. A reliable firm will put the job in writing, link payments to stages of finished work, show insurance and recent projects you can visit, and tell you who will sign off the building regulations. For basement work in particular, ask who is doing the structural design and the temporary works, and whether they have built basements under Camden’s rules before.

You can find registered tradespeople on TrustMark, work through Citizens Advice’s pre-work checklist, and report a rogue trader to your local Trading Standards office.

Figures change: get quotes before you decide

House prices here are UK HPI averages for July 2026; they are provisional, Camden’s are based on relatively few sales, and the August 2026 figures are due on 21 October 2026. Building costs are Checkatrade’s national figures from June 2026 (extensions) and March 2026 (loft types), not Camden quotes, and London work usually costs more. Household figures are from Census 2021. Planning details come from Camden Council’s Local Plan, planning guidance and Article 4 pages as they stood when we checked them, and the new Local Plan could change them once adopted. Check the rules for your own address, and get at least three itemised quotes based on proper drawings before you decide whether to build or move.

Sources: UK House Price Index England: July 2026 (GOV.UK); UK HPI data downloads, July 2026 (full file, Camden E09000007); ONS local house prices: Camden; Census 2021 TS044 accommodation type (Nomis); Checkatrade: house extension costs; Checkatrade: loft conversion costs; Planning Portal: extensions; Planning Portal: loft conversions; Camden Council: development plan documents; Camden Council: draft new Local Plan; Camden Planning Guidance; Home Improvements CPG (January 2021); Basements CPG (January 2021); Camden Council: basement developments; Camden Council: conservation areas; Camden Council: listed buildings; Camden Council: Article 4 directions, heritage and conservation; Camden Council: Article 4 directions, other development; Belsize Article 4 fact sheet (June 2026); Camden: do you need planning permission?; Camden Council: building control; GOV.UK: Party Wall etc. Act guidance; TrustMark; Citizens Advice: before building work; GOV.UK: find local Trading Standards. Data checked 20 October 2026.