Area guide · HP9
House Extensions in Beaconsfield (HP9)
Looking into a house extension in Beaconsfield? HP9 is really two towns wearing one name. The Old Town is a Georgian coaching settlement with a conservation area and listed buildings along its handsome core; the New Town grew from the 1930s onward around the station, and on the Burkes Road side the plot sizes turn properly serious. Both halves produce the commissions we exist for: projects of real scale, spanning double-storey reworks, basements and complete house transformations. Buckinghamshire Council decides planning here, the green belt and the Chiltern edge sit just beyond the town, and we carry every project from first sketch to final sign-off.
Planning in Beaconsfield
Approval in Beaconsfield: two towns, one council
Every HP9 application goes to Buckinghamshire Council, but the test your scheme faces depends on which Beaconsfield you live in. In the Old Town's conservation area the council examines materials, rooflines and street impact closely, and listed properties need listed building consent running beside the planning application. In the New Town the assessment is more conventional, centring on scale, neighbour amenity and design coherence.
Our answer to both is the same discipline: put the ambition where the constraint is not. Old Town projects concentrate their drama on the garden elevation and keep the Georgian frontage untouched, which is the argument officers want to see made. New Town projects, with more elbow room, can afford bolder massing, provided it is composed rather than merely big. This design-first habit is the backbone of our luxury extensions service, and Beaconsfield gives it plenty to work with.
Beyond the built edge, the green belt and the Chilterns fringe impose their proportionality rules, worth confirming before any fringe-plot design begins.
Approval is never automatic anywhere; arriving with a complete, well-reasoned case is the advantage we build for every client.
Local knowledge
Beaconsfield's housing stock, Old Town to New
The Old Town. Georgian and earlier buildings line the old coaching core, many listed, all inside the conservation area. Extending here is craft work: matched brick and lime detailing, hidden structure, additions that defer completely to the street. We scope any listed building consent at the first visit, and the results reward the patience.
Burkes Road. The town's grandest plots, wide, deep and screened, carrying substantial detached houses that absorb the largest briefs comfortably: wrap-arounds (£105,000 to £190,000), double-storey reworks (£110,000 to £230,000), basements and whole-house programmes that finally use the land these houses stand on.
The New Town. From the 1930s outward, the streets around the station filled with solid detached family homes on workable plots. This is prime territory for the kitchen extension (£80,000 to £150,000), the full-width glazed rear and the hip-to-gable loft, much of it possible under permitted development.
The Chiltern edges. Where HP9 meets open country, green belt policy and the Chilterns setting shape what reads as acceptable. Extensions succeed here when they stay proportionate and quiet against the landscape; our guide to extending in the green belt sets out exactly how that judgement works.
Every street is different. That's the point.
We design to Beaconsfield'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 an extension costs in Beaconsfield in 2026
Beaconsfield prices at the top of our map. Figures cover the full build and exclude VAT, fees and kitchen fit-out:
| Extension type | Typical Beaconsfield cost | On-site time | Usual planning route |
|---|---|---|---|
| Side-return extension | £55,000 to £95,000 | 2 to 3 months | Often permitted development |
| Single-storey rear | £65,000 to £125,000 | 3 to 4 months | Often permitted development |
| Kitchen extension (incl. mid-range kitchen) | £80,000 to £150,000 | 3 to 4 months | Often permitted development |
| Hip-to-gable loft + rear dormer | £70,000 to £125,000 | 7 to 10 weeks | Usually permitted development |
| Wrap-around extension | £105,000 to £190,000 | 4 to 6 months | Full application |
| Double-storey rear | £110,000 to £230,000 | 5 to 7 months | Full application |
Plan against £3,500 to £5,500 per square metre, with Old Town heritage detailing sitting naturally at the upper end. How the larger bands break down is covered honestly in our luxury extension cost guide. These are typical market ranges, not offers: each project receives one fixed, itemised quotation after a free design visit, and it holds.
Permissions, handled
Planning in HP9: what actually matters
Old Town or New decides your route. Conservation area rules and possible listed building consent apply in the core; conventional householder assessment applies elsewhere. We establish your position before design starts.
Buckinghamshire usually returns a householder decision in something like eight weeks. We assemble the pack to the council's checklist so validation is immediate and the clock starts on day one.
Permitted development does solid work in the New Town. Standard rear and loft allowances apply where rights are intact, though the conservation area curtails them in the core. Each affected neighbour adds £1,000 to £2,500 where a party wall surveyor comes on board, and we handle those notices as part of the service.
The green belt begins where the town ends. Fringe plots answer to the proportionality test measured against the original dwelling, and we run that calculation before recommending a scheme.
How it works
How it works
- Free design visit. Old Town or New, we establish the constraints on your exact plot and give you real numbers.
- Heritage-aware design. Georgian frontages respected, garden elevations opened up to the full extent the rules allow.
- Consents carried for you. Planning, conservation considerations and any listed building consent all prepared and managed together.
- One fixed figure, then the build. Itemised before we start, certified by building control at handover.
Questions, answered
Beaconsfield extension FAQs
Which authority decides Beaconsfield applications?
Buckinghamshire Council covers all of HP9, and a standard householder application takes about eight weeks to determine. We manage the entire process, including the extra heritage material Old Town schemes require.
Is extending in the Old Town realistic?
Very much so, with the right design. The conservation area demands sympathetic materials and a quiet street presence, and listed properties add a consent layer, but garden-side additions in the right language win approval regularly.
What are 2026 extension costs in HP9?
Budget £3,500 to £5,500 per square metre. Single-storey rears generally run £65,000 to £125,000, double-storey schemes £110,000 to £230,000. All figures exclude VAT and fees; your quote arrives as one fixed, itemised sum.
Do I need permission for a rear extension in the New Town?
Often not. Where permitted development rights survive, the 4m and prior-approval 8m allowances cover many rear schemes, and we secure a Lawful Development Certificate so the position is documented for any future sale.
Does the green belt limit Beaconsfield plots?
Only beyond the built edge. Town-centre and New Town plots are typically unaffected, while fringe properties must keep additions proportionate to the original house. We verify your status at the first visit.
How long will my project run?
Design takes a few weeks, the council decision about eight, and the build three to four months for single-storey schemes, rising to seven for double-storey work. Old Town detailing extends the design phase rather than the programme.
What we build in Beaconsfield
The same team designs, gets planning and builds — one fixed, itemised price whichever route your Beaconsfield project takes.
- Kitchen extensions in Beaconsfield
- Side return extensions in Beaconsfield
- Double-storey & wrap-around in Beaconsfield
- Loft conversions in Beaconsfield
- Luxury & large projects in Beaconsfield
- Annexes in Beaconsfield
Checking the rules for Beaconsfield first?
Nearby areas we cover
What clients say
Rated 5.0 on Google
“The Extension Company built a 5m single storey rear extension on our Victorian terrace in Crouch End. Went down the permitted development route so no planning application needed, which they explained up front and saved us months. Kitchen-diner now opens onto the garden with sliding doors. £87k all in, matched the quote.”
“From the initial site visit onwards to my property in Barnet, we felt that the team actually listened to what we wanted. They suggested a few changes to the layout that we hadn't considered, and those changes have made a huge difference. Would definitely use again and recommend”
“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. The hip-to-gable and rear dormer gave us a big double bedroom with an en-suite. Tidy, professional and finished on schedule. Would recommend to anyone in North London thinking about a loft conversion.”
“We had been putting off our loft conversion for years because the whole process felt overwhelming. The team made it much easier than expected and handled the drawings, planning and build for us. We now have a lovely extra bedroom and shower room.”
“Our wrap-around extension has completely transformed the ground floor. We now have the open plan kitchen and family space we wanted without losing all of the garden. Thanks to everyone involved.”
“Really pleased with the work from The Extension Company. We had our extension done in Hampstead and the whole experience was excellent. Great communication from start to finish, The quality of the finish is excellent and we’re really happy with the result. Would definitely recommend them if you’re thinking about an extension.”
Reviews shown word for word from our Google profile. See 9 more client reviews · Read all 16 reviews on Google
Free site visit
Ready to see what's possible on your street?
Free site visit anywhere in Beaconsfield, honest feasibility advice and a fixed, itemised price — design, planning and build handled end to end by the Pine Grove team.
020 3051 9430Lines open every day, 9am to 8pmNearby areas we cover
The Chilterns
Chorleywood & the Chalfonts · Gerrards Cross · Beaconsfield