Westminster architects | Residential architect projects

At GOAStudio London residential architecture we have extensive experience with working with the Westminster planning department and as your Westminster residential architect we are familiar with all the relevant planning policies that might apply for your home project.

Please see below links to some of our Westminster residential architect projects for ideas and inspiration.

Your brief requirements, the setting of the property, and the immediate context of the property are some of the factors that will determine what home alterations the Westminster planners will be prepared to allow.

We will advise you about what is reasonable to expect to get approval, what might be tricky but possible, and what most likely the planners will say no to.

When it comes to extensions and alterations to residential property the Westminster planning department is yet to prepare a definitive guide about the key principles that will determine the outcome of your planning application.

All relevant advice exists across a number of documents and below we have copied and highlighted extracts of the most relevant current policy and advice for your home project.



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Summary planning and design guide | Westminster residential architect advice

General principles and good practice

  • Works to alter and extend existing buildings will be supported where they are successfully integrated with their surroundings. To achieve this, extensions should be subordinate to the host building, respecting the scale, detailing and materials of both existing buildings and adjoining townscape. Care should always be taken not to disfigure buildings or upset their proportions and to ensure good standards of amenity as set out in Policy 7.
  • Roof extensions can be a practical way to create additional floorspace but can also have a significant impact on the character and appearance of buildings and the wider townscape, and a sensitive approach and highest standards of design will be required.
  • National and London Plan policy identifies the potential for building upwards to increase housing supply. Where upwards extensions will allow the creation of additional residential floorspace to provide family housing or new self-contained residential units and they are sympathetic to the townscape context, they will be supported.
  • Many of Westminster’s residential areas are characterised by terraced housing of consistent design. On terraced houses of the Georgian and Victorian eras, mansards will very often be the most appropriate form of roof extension. However, this will depend on the age and style of the building. Where mansards or other roofs are an established feature within a group of buildings, roof extensions which follow the established pattern will usually be considered acceptable, but they should respect existing architectural features such as chimneys, party wall upstands, parapets and cornices.
  • If properties affected form part of a group or terrace that remain largely unaltered or have a historic or distinctive roofscape integral to the architectural character of that building, further upward extension may be unacceptable, and the design of development proposals will need to be especially carefully considered. Where a terrace retains a uniform roofline with no roof extensions, the addition of one roof extension or multiple roof extensions of different designs can cause harm to the appearance of the roofscape. However, we will consider applications which would take a coordinated approach, adding roof extensions of consistent design to a complete terrace with a uniform roofline. This will typically be on Georgian and Victorian terraces where mansard roof extensions can be accommodated behind a parapet. In such cases we will require extensions across the whole terrace group to be implemented at one time and this may be secured by legal agreement. Upwards extension will usually be inappropriate where a mansard or other later roof extension already exists.
  • The creation of larger extensions to existing buildings may also lead to additional challenges and the capacity to support additional loading will be an important factor in determining the feasibility of delivering such rooftop development. Where substantial demolition of existing buildings will be required to allow for additional height this will be considered having regard to the criteria set out in heritage policy.
  • Even small-scale alterations and additions can have a cumulative impact on townscape character. The design of new doors, windows or shopfonts should be carefully considered to relate sensitively to the existing building and adjoining townscape. Additions such as plant, balustrades, fire escapes routes, telecommunications equipment, cameras and alarms, micro-generation equipment, any associated cables and fixings, as well as air conditioning units, flues and water tanks should always be carefully designed, sited and detailed or screened where appropriate.

Westminster residential architect and planning advice – Extent and depth of basements

Limiting the extent and depth of basement development can help reduce both the risks associated with basement development and mitigate negative environmental and amenity impacts.

Standards for extent of the garden (site area excluding the footprint of the original building) are intended to strike a balance between allowing development, while ensuring a substantial area remains undeveloped (without any impermeable surfacing installed) to ensure adequate drainage and preserve the garden setting.

The most appropriate form of basement development will be no more than one storey (approximately 2.7m floor to ceiling height) below the lowest part of the original floor level. In some cases, an exception could be made for large sites when they are able to accommodate plant and machinery and include appropriate access (e.g. rear or side access) to enable construction without an adverse impact on neighbouring uses or occupiers. The definition of large sites will depend on individual circumstances.

Sufficient soil depth will be required to support sustainable planting. In some circumstances a soil depth of up to 1.5m (plus drainage layer) may be required to support tree growth. Applicants should provide detail of soil profile and composition.

Work to basement vaults can restrict the space available for services in the highway and may make it difficult to access cables, pipes, sewers, etc. for maintenance and to provide essential items of street furniture. In order to ensure that services and essential street furniture can be provided, adequate space must be available between the highway and any excavation proposed under the highway.

Applications adjacent to or affecting the Transport for London Road Network (TLRN) or public transport infrastructure should seek advice from Transport for London.


Conservation areas in Westminster

Since the introduction of conservation area legislation in 1967, the City Council has designated 53 conservation areas which now cover three quarters of the City and include most of the central area.

The character and appearance of these areas vary considerably but all are of special architectural or historic interest. Some, such as the Strand, Trafalgar Square, Whitehall and Westminster Abbey and Parliament Square, have seen development and change from Anglo Saxon times and they contain some of the most historic streets and buildings in London. Others have much more recent origins, such as the Lillington Gardens, Hallfield and Churchill Gardens Estates, where the land was redeveloped for housing after the Second World War.

Westminster residential architect and planning advice – Extensions

Extensions to buildings in conservation areas should preserve or enhance the character or appearance of the area. They should in general be confined to the rear or least important facades and should not upset the scale or proportions of the building or adversely affect the character, appearance or setting of neighbouring buildings.

Extensions to the front or street facades of buildings will normally be unacceptable. This is because it is generally the street facades which make the greatest contribution to the character and appearance of a conservation area. Extensions which involve infilling of light wells at basement level at the front will not normally be acceptable, as these light wells are an important characteristic of many conservation areas, and should be retained.

More change is often possible at the rear, or occasionally the side, of buildings, without affecting adversely the character or appearance of conservation areas. At the rear, buildings have often been subject to many alterations over the years and the uniformity that often exists on the street frontage of a terrace may not be found at the rear. Rear areas are also less public, in that they cannot normally be seen from the street and are only overlooked by adjacent properties.

However, the design of rear extensions and alterations must respect the architectural character of the existing building, the terrace of which it is part (if it is within a terrace) and the conservation area as a whole. Extensions should respect the scale and proportions of the existing building and must be architecturally subordinate to the main building.

Normally the extension should terminate at the penultimate storey level, or lower, thereby leaving the existing parapet line unaltered. The depth of the extension needs to respect any existing addition on the building or the terrace of which it is part. Extensions, which cover the whole of the plot, are normally unacceptable. A significant area of garden or amenity space should normally be retained at the rear. This is particularly important in residential areas but may be less so in some commercial areas, such as Soho. If the building has an L-shaped plan form at the rear then this should normally be retained i.e. the lightwell should not be infilled, except for a glazed, conservatory type extension at ground floor or basement level. Generally, full width extensions are not acceptable, except in certain circumstances at basement level.

Westminster residential architect and planning advice – The design of roof alterations and extensions

Some roofs can be adapted to provide accommodation without major alterations and extensions. Tall pitched roofs may only need internal changes and/or the addition of a rooflight or dormer window. However, other roofs, such as the ‘M’ roof may need substantial alteration or demolition and replacement of the existing roof structure to provide additional accommodation. The form of roof extension that is most common in the City is the mansard roof.

Westminster residential architect and planning advice – The mansard roof 

The principal aim of this guidance is to assist in the design of mansard roofs which will be appropriate extensions on a large number of buildings in the City, where the principle of a roof extension is considered acceptable (see policies DES 6 iii and DES 8 vii).

The guidance is general because it can not deal with every circumstance that exists across the City but it sets out the fundamental rules which need to be followed. It is important to produce a roof form that is appropriate to the building and, if it is a terraced property, to the terrace of which it is part. In some cases it may be appropriate to deviate slightly from the guidance in order to preserve the uniformity that exists in a terrace, so long as the existing pattern of roof extensions is one which is appropriate and one which should be perpetuated.

The mansard roof is not only appropriate for many 18th and 19th century houses but also some classically designed commercial buildings of the 19th and 20th century. It may be inappropriate for many other building types. It is always important to consider carefully the architectural style and character of a building before designing any extension or alteration to it.

Westminster residential architect and planning advice – General rules

1. The principle slope should be pitched no greater than 70 degrees.
2. The upper slope should not normally be greater than 30 degrees.
3. The floor-to-ceiling height should be kept to a minimum. The normal maximum will be 2.3m (in domestic buildings).
4. The intermediate ridge, between the principal and upper slopes (the knee), should be kept as low as possible.
5. The roof should be set back behind a parapet gutter at the front and the rear.
6. The party wall slope should start behind the back line of the parapet coping.
7. The party wall profile should be parallel to the roof slopes, at the minimum upstand permitted under the Building Regulations (1991) of 375 mm.
8. Where a roof is extended the chimney stacks should be raised to retain the same height relationship with the roof.
9. Chimney stacks containing active flues must be raised to at least 1000 mm above the level of the adjoining roof covering to accord with Building Regulations (1991).

There are two types of mansard roof:-
a. The flat topped mansard
b. The double pitched mansard
In many cases the double pitched mansard may be the most appropriate. This is especially so on listed buildings because this form has been used from the early 18th century onwards and because it has a number of advantages, such as providing space for water tanks and other plant, within the roof space.

GOAStudio London residential architecture and interior design is an award-winning practice, specialising in architectural services for residential projects across London.

As your local residential architect our team aims to provide a friendly and professional service for your home project.

Our approach is based on carefully considering the particular aspects of each scheme before coming up with a creative way for you to instil your unique stamp on what we do and how we do it. 

Royal Institute of British Architects (RIBA) and Architects Registration Board (ARB).

Appoint us for Westminster residential architect projects in the following areas:

NW1 Marylebone, Regent’s Park
SW1 Belgravia, Pimlico, St James’s, Victoria, Westminster
Hyde Park, Marylebone, Mayfair, Piccadilly, Soho, West End
W2 Bayswater, Hyde Park, Paddington
W9 Maida Hill, Maida Vale, Warwick Avenue
Kensal Town
WC1 Holborn
WC2 Chinatown, Covent Garden, Holborn, Strand

 Westminster residential architect projects

For more information about the Westminster planning department, policies and requirements please click the link above to be re-directed to Westminster council website.

Name and origin

The name relates to the famous Abbey — ‘mynster’ being Old English for a church. The ‘West’ part simply denotes it as west of the ancient City, and its great church of St Paul. In Anglo Saxon and early Norman times, the area was known as Torneia or Thorney Island, for an islet of that character, upon which the abbey and Palace of Westminster are built. [Londonist.com]

Westminster planning department

You will probably need planning permission if you want to build something new, make a major change to your home – e.g. building an extension, or change the use of your property. There are different rules depending on what you want to do and the relevant planning policy that applies to your property. At GOAStudio we have a proud record of dealing with the local authority planners and building control inspectors and we are on hand to assist with your application and successfully handle every stage of your project.

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We are creative problem solvers who will deal with any construction, planning, and design issue relevant to your home project.

GOAStudio London residential architecture limited, 86-90 Paul Street, EC2A 4NE, Hackney

GOAStudio London residential architecture limited, Chestnut Avenue South, E17 9EJ, Waltham Forest

t: 0203 984 3005
e: george@goastudio.co.uk
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