Area guide · N8
House Extensions in Hornsey (N8)
Planning a house extension in Hornsey? We design, gain planning permission and build extensions and loft conversions across Hornsey's Victorian streets — the old core around St Mary's church tower, the avenues running up towards Alexandra Palace, the lanes along the New River path. Most single-storey rear extensions here cost £45,000–£100,000 to build, applications go to Haringey Council, and both of the most recent local approvals are ground-floor side extensions — the signature move on Hornsey's tighter terraces. Book your free site visit and we'll set out what's realistic on your road, house by house.
Live planning data
What Haringey Council is actually approving in Hornsey right now
We log each residential planning decision across North London as it lands, which means you can read Haringey's actual behaviour instead of guessing at it. From the latest decision period, these are real Hornsey schemes the council approved:
- 42 Park Avenue South, N8 — replacement side infill extension with an oriel window (approved)
- 109 Nightingale Lane, N8 — ground-floor side extension with new windows (approved)
Widen the lens and Haringey passed 32 residential schemes over that same fortnight — a steady flow, and Hornsey is squarely part of it.
Notice that both local approvals are side schemes — and that's no coincidence. Hornsey's terraces are tighter than neighbouring Crouch End's, so the side passage is the most valuable dead space in the house: infilling it transforms the kitchen without sacrificing an inch of garden. Worth clocking too: the oriel window at Park Avenue South is a proper design flourish, and it was approved. Haringey rewards considered detail; it doesn't punish it.
Details taken from Haringey Council's publicly published decisions. Neither scheme is ours — they're included to show the local pattern — and each application succeeds or fails on its own specifics.
Recent extension approvals near Hornsey
We tracked 4 residential extension and loft approvals in the N8 area, most decided by Haringey Council. Most are single-storey rear extension, extension / alterations, side extension. Here are some recent examples that secured approval — useful context for what tends to get through on Hornsey homes:
110 Ferme Park Road Hornsey London
For Demolition of existing rear raised terrace, erection of single storey side infill extension wrapping around to the rear and internal changes at ground floor level. Proposed…
N8
42 Park Avenue South Hornsey London
Replacement side infill extension with oriel window. Reinstatement of window to cellar to front elevation and relocation of boiler flue at the front of the house. Installation…
N8
109 Nightingale Lane Hornsey London
Erection of ground floor side extension and installation of windows on side elevation.
N8
87 Coleridge Road Hornsey London
Demolition of existing extension and erection of ground floor wrap-around extension to the side and rear.
N8
Source: public local-authority planning decision records. Approvals shown are recent examples of schemes granted in the area to illustrate what is achievable locally — they are not necessarily projects undertaken by us. Planning outcomes depend on your specific property and proposal.
Local knowledge
Hornsey's housing stock — and what works on each
Hornsey is the original village in this corner of N8 — older bones than Crouch End, tighter streets, gentler prices. Different streets reward different moves.
The old core around St Mary's church tower. Compact Victorian terraces where every metre counts. The side infill (£35,000–£70,000) is the highest-value move — exactly what both recent approvals did — turning a dark corridor kitchen into a full-width, light-filled room. Where the budget stretches, adding a modest rear extension creates an L-shaped kitchen-diner.
The avenues towards Alexandra Palace. Slightly wider Victorian and Edwardian houses — Park Avenue South sits in this grain. Side infill plus rear extension works well here, as does the loft conversion with rear dormer (£55,000–£100,000) for a bedroom and en-suite with Ally Pally views from the right streets.
The High Street and New River quarter. A more mixed bag — terraces, twentieth-century infill and newer builds near the New River path. Straightforward rear extensions (£45,000–£100,000) and the occasional garage conversion (£18,000–£38,000) where garages exist.
Flats and conversions. Hornsey has its share of converted houses. Flats have no permitted development rights, so every extension or dormer needs a full application — workable, but factor in the timeline.
Every street is different. That's the point.
We design to Hornsey's stock and to what the council demonstrably approves — not to a template. A free site visit tells you what your house can take.
Get my free estimateHonest numbers
What a house extension costs in Hornsey in 2026
Hornsey builds at North London baseline rates with a modest uplift on the prettiest streets — gentler than Crouch End, same builders, same materials. The table gives realistic all-in build ranges; VAT, professional fees and kitchen fit-out are extra:
| Extension type | Typical Hornsey cost | On-site time | Usual planning route |
|---|---|---|---|
| Side-return extension | £35,000 – £70,000 | 2–3 months | Often permitted development |
| Single-storey rear | £45,000 – £100,000 | 3–4 months | Often permitted development |
| Kitchen extension (incl. mid-range kitchen) | £55,000 – £120,000 | 3–4 months | Often permitted development |
| Loft conversion + rear dormer | £55,000 – £100,000 | 6–10 weeks | Usually permitted development |
| Wrap-around extension | £70,000 – £155,000 | 4–6 months | Full application |
| Double-storey rear | £75,000 – £175,000 | 5–7 months | Full application |
| Garage conversion | £18,000 – £38,000 | 4–6 weeks | Usually permitted development |
Hornsey's going rate is £2,800–£4,600 per square metre — the £2,800–£4,200 North London baseline with up to 10% added in the premium pockets. A 16m² side infill, Hornsey's signature project, works out at roughly £45,000–£74,000 on those rates. After the free visit we set a fixed price, itemised throughout, and we hold it — the figure you sign against never creeps.
Permissions, handled
Planning permission in Hornsey — what you need to know
Much of Hornsey extends under permitted development. Semis and terraces can push 3m to the rear — detached houses 4m — without a full application, and the larger home extension scheme's prior-approval route raises those limits to 6m and 8m. Add the generous loft volume allowance and you can see why rear dormers keep appearing across N8.
Side extensions — Hornsey's speciality — are more nuanced. Some qualify under permitted development (single-storey, limited width); many here need a full application because of how tightly the terraces sit. Both recent local approvals went through as full applications with considered detailing, which tells you the route works. We confirm the right path for your house before a single line is drawn.
Conservation status: we check your address against the council's conservation map as part of the free consultation — in conservation areas, permitted development rights are restricted and design expectations rise.
Haringey works through a standard householder application in something like eight weeks. Terraced building means party walls: budget £1,000–£2,500 per affected neighbour if surveyors are appointed — we prepare the notices as part of the job. And wherever works proceed under permitted development, we recommend a Lawful Development Certificate, so everything is watertight when you sell.
How it works
How it works
- Free site visit — we come to your Hornsey terrace, size up the side passage and the roof, and tell you honestly what works and what it will cost.
- Design & drawings — careful plans and 3D visuals that respond to your house's footprint and your household's habits.
- Planning, handled — application drafted, submitted to Haringey Council and chased by us until the decision is in.
- Fixed-price build — our vetted North London tradespeople deliver, building control signs off, and the handover is spotless.
Our work
Recent work near Hornsey
Recently the team has completed a full house transformation taking a family home from 120m² to 360m², a 55m² garden room with kitchen and bathroom, and an Edwardian conversion in Finchley. Tell us your plans at the visit and we'll match them to the most relevant work we've done.
Questions, answered
Hornsey extension FAQs
Is it cheaper to build in Hornsey than Crouch End?
Slightly, yes. Hornsey runs from baseline to about 10% over, where Crouch End carries a 10–15% premium — same trades, same materials, gentler postcode pressure. On a typical rear extension that's a few thousand pounds' difference.
My terrace is narrow — will a side infill really make a difference?
It's the best-value move on a tight Hornsey terrace. You're capturing space you already own — the dead passage beside the kitchen — and turning a corridor room into a proper family kitchen. Both of the latest local approvals, on Park Avenue South and Nightingale Lane, are exactly this project.
Will a side extension in N8 need planning permission?
Sometimes not — single-storey side extensions within strict size limits can be permitted development — but on Hornsey's tighter plots many need a full application. We confirm the route for your address before design starts, so there are no surprises.
What's the realistic planning timeline with Haringey?
Around eight weeks for a householder decision once the application is validated, with certificates of lawfulness usually faster. Add 4–8 weeks before that for design and drawings done properly.
Can I convert the loft on a Hornsey terrace?
Almost always — loft conversions enjoy a generous volume allowance under permitted development, and a rear dormer is the standard approach. The structural solution depends on your roof's build-up, which we assess at the site visit.
How do I know if my street has conservation status?
We check your address against the council's conservation map as part of the free consultation, before any design work starts — it determines whether permitted development applies or a full application is needed.
Nearby areas we cover
What clients say
Rated 5.0 on Google
“Used The Extension Company for a loft conversion on our semi detached in Barnet and couldn't be happier. They explained what was possible at the first visit, sorted the planning side, and gave a fixed price with no surprises at the end.…” read the full review
“Really impressed with the entire project. The side extension and conservatory have been finished to a very high standard and the team made the process straight forward and stress-free. It’s transformed the space and added so much value, would definitely recommend.”
“Brilliant experience with the extension company, transparent from the word go. Completed a double story extension for me and I couldn’t be more pleased. Thank you”
“I got the extension company to do a bathroom refurb for us a January they done a great job they managed to fit in a large shower as well as a bath”
Reviews shown word for word from our Google profile. Read all 8 reviews on Google
Free site visit
Ready to see what's possible on your street?
Free site visit anywhere in Hornsey, honest feasibility advice and a fixed, itemised price — design, planning and build handled end to end by the Pine Grove team.
020 3051 9430Lines answered weekdays 8am to 6pmEvery area we cover
Browse the full areas guide →Enfield & the EN heartland
Cockfosters · Oakwood · Southgate · Winchmore Hill · Palmers Green · Enfield · Edmonton
Barnet borough
Barnet · East Barnet · New Barnet · Hadley Wood · Arkley · Monken Hadley · Hampstead Garden Suburb · Whetstone · Totteridge · Finchley · East Finchley · North Finchley · Friern Barnet · Hendon · Golders Green · Mill Hill · Edgware
Hertfordshire border
Potters Bar · Radlett · Shenley · Elstree & Letchmore Heath · Northaw · Cuffley · Cheshunt · Waltham Cross · Brookmans Park · Hatfield · Hoddesdon
St Albans & the Chilterns
Harpenden · St Albans · Chorleywood & the Chalfonts · Gerrards Cross · Beaconsfield
Haringey & the N postcodes
Muswell Hill · Highgate · Crouch End · Hornsey · Wood Green · Tottenham
North-west London
East & the Essex edge
Stoke Newington · Walthamstow · Chingford · Loughton · Chigwell · Theydon Bois & Epping · Hutton Mount & Shenfield
South-west London & Surrey
Richmond · Wimbledon Village · Esher · Oxshott · Cobham · St George's Hill · Wentworth & Virginia Water
South London & the Surrey downs
Chislehurst · Purley & the Webb Estate · Banstead · Kingswood & Walton-on-the-Hill