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Free 2026 London Planning Report — Rear Extension Drawings in Harefield UB9

Subordinate rear extension on a period cottage in Harefield village UB9, Hillingdon
Harefield · UB9 · Hillingdon

Rear Extension Drawings in Harefield UB9

Fixed-fee, MCIAT-chartered rear extension drawings for Harefield (UB9) homeowners — London Borough of Hillingdon validation and local constraints handled from the start.

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Harefield (UB9) is one of Hillingdon's most rural neighbourhoods — a historic village core wrapped in Green Belt on the northern edge of the borough — and that setting, rather than a standard suburban street pattern, drives how extensions are assessed here. Schemes that keep additions subordinate and in-keeping with the village grain are the ones that move smoothly through the council.

The Harefield Village conservation area protects the scattered building layout, the green and the countryside views, so rooflines, materials and the openness between buildings are treated as part of the heritage. We check both the conservation-area boundary and the surrounding Green Belt designation before advising on what a UB9 plot can realistically support.

Subordinate rear extension on a period cottage in Harefield village UB9, Hillingdon
Isometric illustration of a Harefield UB9 home rear extension drawings design
Proposed floor plan
Harefield UB9

Planning in Harefield (UB9): what to know before you apply

UB9 combines two of the strongest planning controls in the borough — a rural conservation area and widespread Green Belt — so extension scale and siting matter more here than almost anywhere else in Hillingdon. We design Harefield schemes to read as modest, subordinate additions that respect the village setting, which is what the council looks for.

Typical Harefield housing stock

A dispersed village centre of cottages and period houses around the green and St Mary's Church, mixing medieval and post-medieval buildings with Victorian and 20th-century infill, set against open countryside on the borough's northern edge.

Streets we regularly draw for in Harefield

High Street · Church Hill · Park Lane · Rickmansworth Road

Rear Extension Drawings for Harefield (UB9) homes: the package and the process

Every rear extension drawings we prepare for an Harefield property is drawn to London Borough of Hillingdon’s validation standards and tuned to the UB9 constraints above. Here is what the drawing package covers and how the process runs from first survey to approval.

A single-storey rear extension is the most common way London homeowners add space, usually taking the form of an open-plan kitchen-diner that opens onto the garden through bi-fold or sliding doors, with rooflights or a roof lantern bringing daylight deep into the plan. Because depth and height are tightly controlled by permitted development rules and by the 45-degree rule that protects neighbouring windows, the design work sits as much in checking what the council will allow as in drawing what you want.

DrawingsDirect draws rear extensions for permitted development, the larger home extension prior-approval scheme and full householder planning, with structural calculations for the opening and roof produced in-house by our MCIAT-chartered team. If your project also involves widening the kitchen sideways or adding a second storey, see our Side Return, Wraparound and Double Storey Extension pages — many London rear extensions grow into one of those during design.

Do I need planning permission for a rear extension in London?

Many single-storey rear extensions qualify as permitted development, meaning no planning application is needed, provided depth, height and materials stay within set limits. That changes if your property sits in a conservation area or is subject to an Article 4 direction, both of which can remove permitted development rights across a street or borough — in that case a full householder planning application is required regardless of size.

Even where an extension qualifies, most homeowners obtain a Lawful Development Certificate to confirm that status in writing before building — useful for mortgage lenders, buyers and Building Control. We check your property against your borough's constraints before recommending a route.

How deep can a single-storey rear extension go?

Depth is the main constraint on a rear extension, and it depends on your house type and whether you use standard permitted development or the larger home extension scheme.

Permitted development

Standard permitted development allows a single-storey rear extension up to 3 metres deep for terraced and semi-detached houses, or 4 metres for detached houses, generally with eaves height limited to match or stay close to the existing house.

Larger home extension scheme

The prior-approval scheme extends this to 6 metres for terraced and semi-detached houses and 8 metres for detached houses. Your council writes to affected neighbours; if none object within the notification period, approval follows without a full planning application. If an objection is raised, the council assesses the impact on neighbouring light and outlook itself, rather than automatically refusing, so a well-considered design still has a good chance of approval.

Rear extension routes at a glance
RouteWhen it appliesTypical fee
Permitted development (Lawful Development Certificate)Depth within 3m (terraced/semi) or 4m (detached), height and materials within PD limitsPD/LDC pack ~£950–£1,450
Larger home extension (prior approval)Depth up to 6m (terraced/semi) or 8m (detached), with neighbour notificationfrom £1,100
Full householder planning permissionExtension exceeds PD/larger-home limits, or the property is in a conservation area with an Article 4 directionFull Planning pack ~£1,600–£2,400
Planning + Building Regulations (structural)Combined planning and construction-ready pack with structural calculations for the opening and roofPlanning + Building Regs pack ~£2,200–£3,850

Also in Harefield UB9

Planning PermissionPlanning DrawingsArchitectural DrawingsBuilding Regulations DrawingsLoft Conversion DrawingsRear Extension Drawings across HillingdonRear Extension Drawings across London
FAQ

Rear Extension Drawings in Harefield UB9 — FAQs

How much does a rear extension cost to design in London?+
Rear extension drawings start from £1,100, with the final fee set by the route your extension takes — permitted development, prior approval or full planning — and whether you need building regulations and structural calculations bundled in. The fee is fixed and agreed upfront.
Do I need an architect for a rear extension?+
No. DrawingsDirect is an MCIAT-chartered architectural technologist practice, producing the same council-accepted drawings as an architect for a fixed fee typically around 30% lower.
How long does it take to get rear extension drawings?+
Drawings are typically ready around 7 days from survey. Once submitted, councils have a statutory 8-week period to determine a standard householder planning application.
What is the 45-degree rule?+
It is a daylight test many London councils apply to check that a rear extension does not block too much light to a neighbour's nearest window, measured as a line drawn at 45 degrees from that window. We check it before submission, not after a refusal.
Will I need a Party Wall Agreement for a rear extension?+
Only if your foundations or new walls sit on or near the boundary with a neighbouring property. A straightforward rear extension set within your own plot often does not trigger the Party Wall etc. Act 1996, unlike a Side Return or Wraparound extension, which usually does.
Do I need planning permission for a loft conversion in Hillingdon?+
Hillingdon's Metro-land semis and detached houses in Ruislip, Eastcote and Ickenham suit hip-to-gable and dormer lofts, which frequently qualify as permitted development within the volume limits. The exceptions are the conservation areas — Ruislip Village, Uxbridge and Northwood — and green-belt land toward the Colne Valley. We check your address and can confirm permitted development with a Lawful Development Certificate.
How does the Colne Valley green belt affect my Hillingdon project?+
On green-belt properties toward the western edge of the borough, extensions are assessed against strict limits on disproportionate additions to the original dwelling. It does not rule out an extension, but scale and siting matter and the case must be evidenced carefully. We confirm whether your property is green belt and design a scheme that stays within policy.
Does proximity to Heathrow affect my plans?+
It can toward the south of the borough, where aircraft-noise considerations may influence habitable-room and glazing design. We evidence these considerations within the application where they apply so the council can validate and approve without repeated revisions.
How long does Hillingdon Council take to decide?+
Hillingdon determines most householder applications within the statutory eight-week period once validated; green-belt and conservation cases can involve additional consultation. We prepare Hillingdon submissions to the council's validation checklist to avoid the drawing queries that cause most delays.
How much do planning drawings cost in Hillingdon?+
We work to a fixed fee agreed upfront, usually around 30% below an architect's charge for the same council-accepted drawings, with free redraws until Hillingdon approves. A dormer loft, a suburban extension and a green-belt case differ in the evidence required, so we confirm the fee once we understand your project rather than billing by the hour.
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