Architect in Westminster for Planning Applications and Extensions

Horizon Architecture provides planning, extension, loft conversion and technical drawing services across Westminster, with active council monitoring and coordination from survey to decision.

Article reviewed 1 August 2026

Planning applications and approvals in Westminster

Development takes place in one of the world’s most valuable and historically sensitive property markets. Even small changes can need exacting design and heritage justification. The planning authority received 5,458 applications in the latest annual reporting period and issued 4,602 decisions. Of those decisions, 3,954 were granted and 648 were refused, equivalent to an authority-wide refusal rate of 14.1%. These totals provide useful context but do not predict the outcome of a specific property or proposal.

Approval depends on the site, planning history, Local Plan policies, the London Plan, permitted-development position, design quality, neighbour effects, heritage and environmental constraints. We review those matters before fixing the application strategy.

An active planning service rather than a submission-only service

We aim to make the process effortless for the client. After submission we check whether the application has been validated, monitor the council register and key dates, and remain available to provide information that is reasonably required. Where the case officer identifies a specific concern and is willing to consider an amendment, we assess it quickly and coordinate an appropriate response rather than allowing avoidable delay.

• Confirm the correct application route and local planning authority.
• Review planning history, designations, policy and neighbouring development.
• Prepare coordinated existing and proposed plans, elevations and sections.
• Compile the application forms, ownership certificates and supporting documents.
• Monitor validation and address reasonable validation queries.
• Track the application during determination and remain available to the case officer.
• Coordinate focused revisions or extra information where this is proportionate and may assist approval.
• Prepare Building Regulations drawings and coordinate the technical team after permission.

Conservation areas and heritage in Westminster

Westminster City Council contains conservation areas including Mayfair, Belgravia, St John’s Wood, Knightsbridge, Harley Street, Marylebone, Bayswater, Soho, Covent Garden and Pimlico. A conservation area does not prevent thoughtful change, but the council must give special attention to preserving or enhancing its character and appearance. This commonly affects roof alterations, dormers, front elevations, windows and doors, boundary walls, hardstanding, demolition, plant, materials, trees and development visible from public viewpoints.

Westminster contains numerous conservation areas, listed buildings and Article 4 Directions. High-value residential and commercial proposals often need coordinated heritage, townscape, servicing and acoustic evidence.

For a property in or near a conservation area we review the relevant appraisal and management guidance, identify features that contribute to significance and explain how the proposed design responds. A heritage statement, schedule of materials, detailed joinery information, streetscape drawings or verified views may be needed depending on the project.

Property types and recurring planning issues in Westminster

The borough includes listed terraces, townhouses, mansion flats, mews, garden squares, hotels, offices, retail, hospitality and internationally significant heritage assets. Recurring planning considerations include listed fabric, formal terraces and squares, townscape views, roofs and basements, plant, servicing, extraction, noise, transport and cumulative intensification. The correct solution is therefore site-specific: a form of development that is acceptable on one street may be unsuitable on another because of plot pattern, designation, visibility, neighbour relationships or planning history.

Projects we can prepare and coordinate

• Rear, side-return, wraparound and first-floor house extensions.
• Loft conversions, dormers, hip-to-gable and mansard proposals.
• Internal reconfiguration, refurbishment, façade and window alterations.
• Flat conversions, changes of use and Houses in Multiple Occupation where policy permits.
• Retail, office, hospitality, healthcare and mixed-use planning applications.
• Listed-building and conservation-area applications.
• Building Regulations drawings and technical packages after planning approval.

Supporting reports and other professionals

We coordinate the architectural work with other disciplines where the planning authority or project requires them. This avoids fragmented information and gives the client one coordinated route through the process.

• Structural engineering for beams, openings, lofts, foundations, basements and stability.
• Heritage statements and specialist conservation advice.
• Acoustic reports for plant, commercial uses, conversions, entertainment and transport noise.
• Arboricultural surveys and impact assessments where trees may be affected.
• Flood-risk, drainage, sustainable drainage and build-over advice.
• Daylight and sunlight, transport, servicing, extraction, fire, energy and building-services information.
• Construction management, ecology, contamination and land-quality information where relevant.

How much does a planning application cost in Westminster?

The principal statutory planning application fees are set nationally rather than by each London borough. From 1 April 2026, a typical householder application to alter or extend one house costs £548. Other development types use different calculations. Planning Portal service charges, council pre-application advice, Building Control, specialist reports and professional fees are separate.

Horizon Architecture charges £100 for planning application submission, with planning drawings starting from £1,400. We confirm the architectural scope, likely statutory fee and foreseeable specialist inputs before appointment.

Neighbourhood planning guides in this borough

Frequently asked questions

Planning guides for every Greater London borough

Select another borough below. Every guide uses the same official reporting period and explains conservation controls, current statutory fees and Horizon Architecture’s active application-management service.

Related architectural services

All London borough planning guides · Neighbourhood planning guides · Planning applications · Building Regulations drawings · Conservation area architect · Planning refusal help