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Gaining Necessary Consent

Extensions to dwellings – Notification of Prior Approval

Planning permission guidelines for single storey extensions have recently changed. It is now possible under the “Notification for prior Approval” system, introduced by the government for works commenced in the next 3 years to encourage growth in the building industry, to request a projection of up to 6m on rear extensions to semi-detached and terraced properties, and 8 metres on detached properties.


This only applies to single storey rear extensions on residential dwellings, and is subject to neighbour consultation. Where the local authority deem that a certificate of approval cannot be issued, then the full planning process as described below will be applicable. To benefit from this new, temporary legislation, the extension must be completed on or before 30th May 2016.

Permitted Development – Lawful Development Certificate

Most dwellings will have permitted development rights intact. This means that, subject to the proposed works, it may be possible to design and build an extension, loft conversion etc. without the need for full planning permission. Where works would be classed as permitted development, an application for a “lawful development certificate” can be carried out, this provides you with written verification from the council that the proposal is lawful.


Generally, an extension will require planning consent if;


  • More than 50% of the curtilage of the property is covered – note that previous extensions, detached garages, sheds etc. must be taken into consideration
  • The height of the extension exceeds that of the original dwelling
  • The height of the eaves exceeds that of the original dwelling
  • The extension is to the front of the property (or side of the property to corner plots)
  • The extension is to the rear of the property and exceeds more than 3m projection for semi-detached or terraced dwellings, and 4m for detached dwellings (notwithstanding the above Notification for Prior Approval guidelines). Single storey rear extensions should be no higher than 4m to the top of the roof from adjoining ground level
  • The extension is within 2m of the boundary, and the eaves is more than 3m high
  • The extension is to the side of the property, and more than 4m high, or has more than 1 storey, or is more than half the width of the original property
  • Materials to be used on a project should, where possible, match the existing dwelling. Where this is not the case, planning consent may be required
  • Two storey rear extensions can sometimes be permitted development, provided that they do not project more than 3m from the original rear wall of the dwelling, and should be no less than 7m from the opposite boundary.

When determining the width or depth of a proposed extension, it is important to consider theoriginal building, as existing extensions will need to be taken into consideration.


Previous extensions to a property will generally not have permitted development rights.This means that if, for example, you are proposing to construct a rear extension across thefull width of your property, and the property has previously been extended to the side, the proposed new extension will only be permitted development if it is sited only across the original part of the dwelling.


Note that installations of verandas, balconies, chimneys etc. will generally require planning consent.

Removal of Permitted Development Rights

Note that some properties, in particular newer buildings or those built as part of an estate,will often have a removal of permitted development rights. Certain geographical locations such as areas of natural beauty, or conservation areas, may also be subject to specific removal of permitted development rights.


This is imposed by the local authority, and may mean that the above permitted development guidelines cannot be applied. In this instance,planning permission will be required. Flats will generally have permitted development rights. Projects sited on land not registered as residential (such as farmland etc.) will also generally have permitted development rights removed.

Green Belt / Rural Classification

Development within the Green Belt is subject to certain restrictions not applicable to urban areas. Permitted Development rights are generally the same, and so the above requirements can be applied. However, in instances where planning permission is required the local authority will place restrictions on the amount of development allowable. This is generally around 30 % above the original floor area of the dwelling, although this can sometimes be negotiable with the relevant authority planning office. Note that existing extensions etc. will often count towards this overall area allowance.

Listed Building Consent

Planning Permission would be sought by Add A Room on our client’s behalf. The process is that full plans are submitted to the council for review. As part of their own system, the council will then write to any affected neighbours, and other bodies such as the Parish Council, where relevant. Any comments will be given consideration, and the council will reach a decision in generally around 8 weeks. This can take longer where, due to specific factors, the decision needs to be reached at committee instead of individually by the planning officer.


In instances where planning permission were to be refused, it is usual that a free re-submission of plans can be carried out on works of the same description, and within 1 year of the date of refusal.


If planning permission is only required due to a removal of permitted development rights on your property, it is usually the case that no fee to the local authority will be applicable, even on the first application.


Add A Room Ltd would always liaise with the relevant authorities throughout the application process, and act as agent on your behalf, to ensure that the application runs as smoothly as possible.

Listed Building Consent

Where full planning permission is not required, Add A Room will apply for a Certificate of Lawful Development on our client’s behalf. This provides you with written consent from the council that the proposed works are lawful, in the absence of a planning grant. The general process and timescale is similar to a full application, although neighbours are not consulted in writing.

Protected Species

Dependent on the nature of your project, if your property is in an area noted for the presence of protected species it may be necessary to provide proof that no protected species will be affected by the proposed works. Typically, this could be a loft conversion to a property which could potentially be used as a roost for bats, or construction work near to a badgers set, or a pond / watercourse with newts. In these instances, a specialist report may be required prior to commencement of works.

Prior Consultation

In some instances it will be worthwhile for us to consult on your behalf informally with the local authority planning office prior to submission of a formal application. This can be especially important if the works are in a prominent location or conservation area, green belt etc., and of a nature which could be contrary to the local authority’s planning guidelines.


Conservatories are subject to the same planning permission requirements as other works, however are generally considered exempt from building control below 30sqm floor area, provided that exterior doors are retained between the dwelling and conservatory, and the heating is retained separate from the main central heating of the dwelling. If you would prefer the conservatory to be open plan, then we can provide a SAP (heat loss) calculation for the project, and in this instance we would submit for building control approval. Please refer to above planning permission, permitted development guidance & building control notes.


Orangery style extensions are a hybrid of a conservatory and a traditional construction, and will be subject to building control approval. Heat Loss calculations could be required to prove thermal compliance.


Outbuildings such as detached Garages, stores, garden rooms etc. can often be built as permitted development, provided that the building is fully detached from the dwelling, and falls below the required threshold for eaves and ridge height. Building control for non- habitable outbuildings is generally not required, where the floor area is less than 30sqm.


Note that the use of an outbuilding must be recreational and subsidiary to the main dwelling, for example a detached annexe building providing sleeping accommodation will not be classed as permitted development.


Porches will often not require planning consent, provided that the area created is less than 3sqm measured externally. The maximum roof height of the porch must be no more than 3m above ground level, and the porch must be no less than 2m from the boundary of the dwelling with any public highway. To be classed as a porch, an external grade, lockable doors must be retained between the porch and the main dwelling. If separated from the dwelling by external grade, lockable doors, a porch will often be exempt from building control.

Hard standing Areas

The addition of hard standing areas for parking etc. will generally be classed as permitted development, provided that where the new hard standing is between the property and the public highway, and is more than 5sqm in size, the proposed hard standing should be either of porous construction, or should drain to a permeable area within the curtilage of the dwelling. This is to prevent surface water runoff from hard standing areas from overloading the main storm drains within the public highway.

Loft Conversions

Loft conversions will often not require planning consent ie. Would be classed as permitted development, subject to the following limitations;


  • No part of the extension should exceed the height of the existing dwelling
  • No part of the extension should be built forwards of the front facing roof slope
  • The cubic volume of the roof addition should be less than 40 cubic metres for terraced
  • dwellings, and 50 cubic metres for all other dwellings. When calculating this volume, it is important to note that previous additions and extensions to the roof must be taken into consideration
  • Side facing windows (such as a landing window to a new gable wall) must be fixed
  • closed below 1.7m above finished floor level, and glazed with obscure glass
  • Materials used on a loft conversion externally should match the existing dwelling
  • Verandas, balconies, chimneys etc. will generally require planning consent

As for standard extensions, where planning consent is not required, Add A Room would apply for a Certificate of Lawful Development on your behalf.

Balconies and Juliet Balconies

The construction of a raised terrace or balcony will generally require planning consent. This can, subject to ground levels, include decking, terracing etc. to a garden as well as balconies to the dwelling. When determining planning consent for a raised balcony or terrace, the local authority will need to consider the potential impact through overlooking and loss of privacy to neighbouring properties.


A Juliet balcony consists of inward-opening French doors, with a guarding installed across the opening. The requirement for planning permission to construct a Juliet balcony can be specific to the site and direction in which the balcony is to face, but a rear-facing juliet balcony will often not require planning consent. Juliet balconies do not form any additional outside space, and so issues of overlooking are minimised. The same applies for specialist balcony systems such as the Velux Cabrio product, which we have recently installed to several projects.

Balconies in general will be subject to building control approval.

Garage Conversions

It will generally be possible to convert a garage into habitable space, without requiring planning consent. The instances in which planning consent would be required are if a specific covenant relating to the property advises that it should be retained as a garage (often the case with newer dwellings or where off-street parking is limited), or if the garage in question forms part of a previous extension to the property. If planning consent is required, then, subject to the number of bedrooms in the property and the existing parking arrangements, it may often be necessary to provide additional off-road hard standing to replace the garage.
Garage conversions require building control approval as per standard extensions, although it is generally a straightforward process of installing additional insulation to existing floors, walls and ceilings.

Party Wall Act

The Party Wall act is a legal requirement for various projects, notably where constructing close to a boundary, or setting steel beams (for example on a loft conversion) into a Party Wall. For further information on the Party Wall Act we would recommend an internet search on the “Planning Portal”, this provides set examples and general requirements.


Please follow the attached link to the Planning Portal for further information on the requirements of the Party Wall Act. Please contact us if you need assistance or guidance in


Local Water Authority Limitations

Recent changes to water board legislation has re-defined the terminology of a public sewer.


It is now interpreted that if a sewer crosses onto or through your property, from another property, ie. You are not at the head of the run, then this will be classed as a public sewer. In most instances our approved inspector will be able to sign off works over or near to a public sewer. Where a manhole on a public sewer is to be moved, or a new connection made, or the sewer is larger than 100mm diameter or deeper than 3m, then the water authority must provide their own written approval prior to commencement of works. Please contact us if you need assistance or guidance in the above.


Please note, all the above are general guidelines and should be treated as such. Further information can be obtained on the Planning Portal website.


Our design team will offer specific advice relating to your project and the permissions which may be required.

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