Rear Extension in Hampstead NW3

Why Hampstead Properties Choose Us

Victorian/Edwardian terraces, conservation area, Heath proximity. Large detached and semi-detached houses, many Grade II listed. Our team works exclusively in NW London, bringing detailed knowledge of Camden planning requirements and the specific challenges of Victorian/Edwardian terraces & detached stock. As a designated conservation area, every project in this postcode requires specialist handling — knowledge our team has built over years of delivering projects here.

Planning Authority

Camden LBC

Average Property Value

£2,800,000

Conservation Area

Yes — planning applies

Typical Project Cost

£65,000–£140,000

How a Rear Extension Works — Step by Step

1. 1

   Site Survey and Design Brief

   We survey the rear garden, measure existing room layouts, and establish the maximum footprint permitted by the planning authority. We confirm the position of any drainage runs, manholes, and underground services that will affect foundation design. From this we establish the design brief with your architect.

2. 2

   Planning Application or Permitted Development Confirmation

   In conservation areas and Article 4 zones, full planning permission is required. Where PD rights exist, we apply for a Lawful Development Certificate to confirm permitted development status before work starts — protecting your investment against future challenges at sale. We manage the full planning or LDC process.

3. 3

   Architectural Design

   A RIBA architect produces construction drawings including floor plans, sections, elevations, and roof details. In conservation areas the external materials — brick, render, glazing — are selected to satisfy the design requirements of the planning authority. Full plans are submitted to building control alongside the structural engineer's calculations.

4. 4

   Structural Engineering and Foundation Design

   A structural engineer designs the foundations (strip, pad, or raft depending on soil conditions), the steel or timber frame for the roof structure, and any steels required to open up the rear wall. London Clay conditions are well understood by our engineers — foundation depths of 1.0–1.5m are typical but may be deeper near trees.

5. 5

   Groundworks and Foundations

   Excavation commences for the extension footprint, any utility diversions are completed, and the foundations are poured. Underground drainage runs are laid to connect the new extension's soil stack and ground drainage to the existing drain. Building control inspects the foundations before pouring commences.

6. 6

   Superstructure, Roof, and Weatherproofing

   Blockwork walls are built from the foundation up. The roof structure — typically a flat warm roof or a lean-to with a conservation rooflight — is constructed and made weathertight before any internal work begins. External cladding or render is applied and external joinery installed.

7. 7

   Rear Wall Opening and Steel Installation

   With the extension weather-tight, the existing rear wall is opened up under the new structural steel lintel or frame. Temporary props support the structure while the masonry is removed. The new bifold, sliding, or fixed glazing is installed, transforming the connection between house and extension.

8. 8

   First Fix, Screed, and Internal Fit-Out

   First fix electrics, underfloor heating pipes, and plumbing are installed before the screed is poured. Insulation to Part L standards is fitted. Plastering, second fix, kitchen installation, and decoration follow. Building control issues the completion certificate at sign-off, confirming compliance.

Rear Extension in Hampstead — Planning and Local Considerations

Article 4 Direction applies across Hampstead NW3 — all single-storey rear extensions require planning permission from Camden LBC regardless of size. The Hampstead Conservation Area officer assesses external materials (brick, render, glazing) against the character appraisal. London Clay and Hampstead drift geology require structural engineering attention, particularly near the Heath where groundwater levels fluctuate seasonally. Pre-application advice from Camden is strongly recommended before finalising the design.

Frequently Asked Questions