Daylight & Sunlight Matters for those Planning an Extension or New Build

When embarking upon an exciting new project, such as extending your home, or possibly even a bigger scheme like building your new home from scratch, you should ensure that you discuss the massing and potential impact upon neighbours with your designer.

Many Local Authorities have policies that seek to ensure access to daylight and sunlight to neighbouring habitable room windows, and that sunlight to the neighbours’ principal garden is not adversely affected by a development.

Even in the absence of such a specific local policy, National Planning Policy stipulates that amenity should be considered, and thus, where your Local Council’s policies are not clear on the issues of Daylight and Sunlight, failure to assess can still lead to a neighbour challenging a planning decision if proper consideration has not been given.

The most widely recognised and used document for assessing good Daylight and Sunlight design, is “Site Layout Planning for Daylight and Sunlight – A Guide to Good Practice, 2nd Edition” by Paul Littlefair. This is a nationally recognised publication, and whilst not mandatory, it has been adopted by many design practitioners, planning consultants and Local Authority Planning Departments throughout the UK.

As a result of this, if your proposed extension does not meet the tests with this Guide (formally known and still widely referred to as BRE 209), and thus causes adverse impact to your neighbours’ home, planning permission can be refused, or, you may be asked to adapt your design to eradicate the harmful impact upon your neighbours’ property.

You may be asked to demonstrate that your design will not adversely affect your neighbour(s), by providing a Daylight and Sunlight Assessment to accompany your planning application.

If this does happen, we can help.

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    “Following a rejection of our plans for the building of a new house, by the Planning Authority, due to the effect of the proposed development upon the living conditions of the neighbouring properties, with particular regard to outlook and daylight / sunlight, we decided to appeal the decision. As part of our appeal we commissioned a Daylight & Sunlight Assessment from Smith Marston which reached an entirely different conclusion to the planning authority. The report was crucial, with the Planning Inspector concurring with it’s conclusions, and the decision of the planning authority overturned. We found the work undertaken by Smith Marston excellent, objective and in accordance with Industry standards, and would have no hesitation in recommending them.”

    Mr Brown
    “Smith Marston helped us gain planning approval on our two-storey extension after a number of objections from neighbours. The advice they gave and the detailed letter to the council gave factual information to dismiss unfounded objections.”
    Mr A, Warrington

    “A Local Authority Planning Officer required confirmation that a proposed housing development would not cause any loss of sunlight to an adjacent property. On this basis Smith Marston completed a BRE garden sunlight test which on completion satisfied the planning officers concerns. This specialist report proved to be invaluable in securing the planning approval for our client.”

    Keith Butler, KB Design

    Frequently Asked Questions

    From a planning perspective, when considering the impact your extension will have upon the daylight and sunlight on your neighbour’s hall and stairs, then no, these would not be considered by the Local Authority as these areas would be classed as ‘non-habitable’ areas. However, you should be aware that such areas CAN have a legal right to light and so even if you get planning permission, you could still potentially cause a legal injury to your neighbour’s home. The extension you describe is one of the most common legal right to light problems we come across, and so the risk should not be ignored.

    Of course. We can take your architects drawings and prepare a 3D computer model to calculate how much daylight and sunlight your neighbours will enjoy pre and post development. We can also ascertain how many sunlight hours your neighbour’s garden will be able to receive. If the impact is to such an extent that it will cause you problems with your neighbours, or, is to a level that might hinder you gaining planning approval, we can help to redesign the ‘mass’ of your proposal by calculating the amount of ‘cutback’ you would need to undertake.

    Unfortunately, this is quite common. Whilst more common to consider the impact of a new scheme on a neighbouring property, Planning officers can also consider the daylight and sunlight availability to a proposed scheme as well. We have had several projects where planning officers have ‘felt’ a new dwelling would be poorly lit and have been minded to refuse consent. Some have even refused consent and forced the applicant to go to Appeal. In these situations, a ‘Within’ Daylight and Sunlight Assessment could be invaluable for you. If a planning committee (or Planning Inspectorate at Appeal) is faced with considering the ‘gut instinct’ of a planning officer versus a professional study, based upon computer modelling, and adopting widely accepted, industry measured criteria, the latter puts you in a much stronger position.

    Not really. There are genuine times when such studies are necessary, and these are when the ‘rules of thumb’ tests fail (see our e-brochure here). However, in your case, your drawings show that your new extension does not cut through a line drawn at 25-degrees from the horizontal plane from the centre of your neighbour’s window. Therefore, the 25-degree rule of thumb test is not breached and there would be no risk to your neighbour’s windows. Furthermore, in your case the neighbour’s windows are ‘non-habitable’, which do not require consideration. In situations like this, we have in the past written to the Local Authority in question to explain that a study should not be necessary to ask them to retract the request for such a report. Many Local Authorities will do this if we can demonstrate why there is no risk. Unfortunately, the request you have received may have stemmed from a ‘tick-list’ approach by somebody in the Validation team, without careful thought having been given as to whether such a report is necessary.

    Technical Information on Daylight & Sunlight

    A neighbour to a proposed development may have grounds to object within the planning process based upon loss of daylight and sunlight.

    In such circumstances, a neighbour wishing to object to a proposed development may wish to add some weight to this objection by arranging for a formal assessment to demonstrate whether the scheme would fail the tests described within the BRE document. Although there may be overriding factors which would still lead a Council’s planning department to grant planning permission despite the failure of the scheme in respect of the BRE guidance tests, this is a serious ‘material consideration’ matter which could give grounds for refusal of an application for planning permission.

    More Details

    This considers only the hours of sunlight a window will receive over a 12 month period. Because the test relates only to sunlight, only windows facing within 90 degrees of due south are considered under the methodology contained with the BRE document Site Layout Planning for Daylight & Sunlight.

    The guidance is that main windows should receive at least 25% of the ‘total probable sunlight hours’ for a 12 month period. This should include 5% of the total probable sunlight hours over the winter months between 21 September and 21 March.

    As for the Legal Right to Light, this takes no account of direct sunlight and assesses only the amount of diffuse light within a room related to an affected window.

    The principal method of assessing this is a measure of the amount of sky visible from the window of an affected room. This assessment component is called the Vertical Sky Component (VSC). For a window of a room to be adversely affected under the BRE guidance, the window must have a view of less than 27% of the ‘dome of the sky’ (a VSC of less than 27%) and the VSC must be less than 0.8 times its previous value.

    A further more detailed assessment is called the Average Daylight Factor. This is a measure of the actual likely natural diffuse daylight in a room taking account of various matters influencing this such as the reflectivity of surfaces and the glazing in the window. The no sky-line is a measure of those parts of the room which have no view at all of the sky at all.
    The BRE guidance suggests that consideration of sunlight to external areas should normally include:

    • Gardens, usually the main back garden of a house, and allotments;
    • Parks and playing fields;
    • Children’s playgrounds;
    • Outdoor swimming pools and paddling pools;
    • Sitting-out areas, such as those between non-domestic buildings and in public spaces;
    • Focal points for views, such as a group of monuments or fountains.

    The BRE guide recommends that at least half of the garden/amenity area should receive at least two hours of direct sunlight on 21 March.

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