House Extension in North & North West London — Rear, Side-Return & Wraparound

What do you need?

Choose the job. Each one says what to send, and whether to call.

• A rear or side extension

  Photograph the garden elevation and say whether the house is a flat.

  Send this in a brief

• Planning and the build

  Send any drawings you already have. Consent stays with the authority.

  Send this in a brief

Frame the extension around household use and the existing plan

A house-extension brief should explain what the existing home cannot do and how the proposed space should connect to it. A rear family room, side-return kitchen, utility addition, accessible room or two-storey enlargement creates different daylight, circulation, privacy, service and structural questions. Mark which walls and rooms may change, how the garden should be reached and whether the home remains occupied. “Wraparound” or “rear extension” describes a form, not an evidenced design. The first output should be a clear brief and feasibility route rather than an assumed footprint or generic square-metre price.

Survey boundaries, levels, structure and buried constraints

Measured information should cover the house, previous additions, plot boundaries, ground and threshold levels, drainage points, trees, visible services, neighbouring buildings and construction access. Existing drawings, title information, planning history, surveys and service records should be assembled where held. A photograph cannot establish boundary ownership, foundation condition, drain ownership or ground bearing capacity. The designer and relevant specialists should identify what further investigation is proportionate before foundations, openings or drainage diversions are fixed. Unknowns belong in the survey plan and quote assumptions, not in confident marketing language.

Determine planning status from the complete proposal

Some house enlargements can fall within permitted-development rights in England, but only where all current conditions, limitations and cumulative-development tests are satisfied. Government technical guidance also explains that these rights do not remove other consent regimes and do not apply in every property context. Previous extensions, original-house interpretation, designated-land rules, removed rights and the relationship between rear, side and roof work can change the answer. The relevant authority or appointed planning professional should assess the exact design and address; an area hub cannot grant permission or declare an application unnecessary.

Coordinate foundations, openings and the retained building

The structural package should address the proposed foundations, ground conditions, nearby structures and drains, new walls and roof, lateral stability and openings through the existing house. Temporary support and the sequence for forming an opening matter as much as the final beam. Most extensions require Building Regulations approval, and the control route should be agreed before controlled work starts. Calculations, details and inspection stages need to align with the architectural design. A structural allowance without defined bearings, supports, fire protection and making good is not a complete construction scope.

Design drainage, thresholds and weatherproof junctions early

An extension changes roof runoff, external ground, thresholds and sometimes foul or surface-water routes. Kitchen, utility or bathroom layouts can add new drainage demand and coordination. Existing drains may cross the proposed footprint or involve a water-company or other approval route, but ownership and condition must be checked rather than assumed. The package should show roof drainage, waterproof junctions, damp protection, finished levels and how the new envelope meets the retained building. Delaying these decisions until groundworks or roofing makes avoidable changes more likely and can compromise access for inspection.

Treat boundaries and party-wall procedure as owner matters

Building on or near a boundary, working on a party structure or excavating near a neighbouring building can engage the Party Wall etc. Act. Government guidance describes this as a separate legal framework from planning and Building Regulations. The proposed foundations, wall position and structural openings need enough definition for the relevant owners and advisers to decide what procedure applies. A neighbour’s informal support is not the same as every required notice or consent, while a party-wall award does not determine the planning application. Responsibilities and lead times should be visible in the programme.

Plan an occupied-home project and its construction duties

Access, protection, temporary security, dust separation, utilities, deliveries, waste and welfare arrangements shape whether the house can remain occupied during work. Under CDM 2015, HSE explains how domestic-client duties normally pass to the contractor on a single-contractor project or the principal contractor where more than one contractor is involved, unless the permitted written arrangement applies. The project team and roles should be named rather than implied. A construction phase plan, site controls and realistic sequencing are part of delivery; a polished design alone does not manage safety or household disruption.

Price and hand over the accepted extension package

A useful proposal distinguishes design and professional fees, applications, investigations, structural work, groundworks, drainage, envelope, scaffold or access, services, finishes, protection, waste, allowances and exclusions. It should state which decisions remain provisional and how changes are approved before extra work proceeds. Programme milestones normally depend on design, consent, neighbour procedure, procurement, opening-up and inspections, so a fixed completion promise is not justified before those facts are known. Handover should assemble the agreed drawings, calculations, approvals, inspection evidence, product information, commissioning records and a written snagging status.

Frequently Asked Questions

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