Objecting to an extension on daylight grounds

An objection about loss of light works when it describes a specific window, in a specific room, and explains geometrically why the proposed extension will block the light reaching it. An objection that says the extension will be overbearing and make the garden gloomy will be read, recorded and given almost no weight. Loss of daylight and sunlight to a habitable room is a material planning consideration. Loss of a view is not, and neither is the effect on your property value.

The difference between those two objections is about a page of work.

What the council can and cannot take into account

Case officers weigh material considerations, and on a householder extension the list is short: daylight and sunlight to neighbouring habitable rooms, overlooking and loss of privacy, an overbearing or enclosing effect, noise and disturbance from the use, design and its effect on the character of the area, parking and highway safety, and trees.

The list of things that cannot be taken into account is longer than most objectors expect. Property values, loss of a view, disruption during construction, the applicant's personal circumstances or conduct, boundary and ownership disputes, and covenants on the title all fall outside planning.

Rights of light sit in a category of their own. A right to light acquired over time is a private legal right enforceable in the civil courts, and it is entirely separate from the planning judgement about daylight. A council cannot refuse permission to protect your private right, and a grant of permission does not extinguish it.

The 45 degree and 25 degree tests

Most councils publish a householder design guide that applies a 45 degree test, and it is the workhorse of householder daylight assessment.

The method is simple enough to do yourself with a tape measure and a plan. From the centre of your nearest habitable room window, draw a line at 45 degrees in plan towards the proposed extension. Then draw a 45 degree line in section from the same window to the top of the proposal. If the extension crosses both lines, the council's own guidance usually indicates unacceptable harm and the officer has to justify departing from it.

The 25 degree test comes from national good practice guidance on site layout. Measured from the centre of the lowest window of the affected room, if the new obstruction subtends an angle of less than 25 degrees to the horizontal, daylight is unlikely to be materially affected. Above that angle, further analysis is warranted.

Check your council's adopted guidance before relying on any of these. Some authorities apply 45 degrees only to the rear, some measure from the window reveal rather than the centre, and a few use a 30 degree line in tighter urban settings.

Where BRE guidance fits on a householder case

The BRE guide to site layout planning for daylight and sunlight sets out numerical measures: vertical sky component, the no-sky line, and annual probable sunlight hours, each with a retained proportion of the former value as the test of acceptability.

Those measures were written for site layout planning, and councils rarely require that analysis for a single storey rear extension. Asking for a full assessment on a small householder case usually gets a polite refusal.

Where it does become relevant is a two storey extension close to a boundary, a first floor side extension opposite a neighbour's only window, or a scheme where the 45 degree test is breached and the applicant disputes the consequence. If you are in that position, say in your objection that the 45 degree test is breached and that the applicant has produced no daylight analysis to show the effect is acceptable. That puts the burden where it belongs.

Describing your own window properly

Officers cannot assess what they cannot picture. Give them the facts.

• Which room the window serves and what it is used for. A living room or bedroom carries more weight than a utility room, and a kitchen sits somewhere in between depending on whether it is used for dining.
• Whether it is the only window serving that room. A single aspect room is the strongest case there is.
• Its orientation and the distance from the window to the boundary and to the proposed wall.
• The window's height above ground and the height of the proposal opposite it.

Two photographs help more than two pages of text: one from inside the room looking out, and one from the garden showing the boundary and the existing building line. Add a rough sketch section with the measurements marked. It does not need to be to scale, though it helps if it is.

An illustrative example: a 1930s semi where the neighbour proposes a two storey rear extension 3.5 m deep on the party boundary. The affected room is a ground floor kitchen and dining room, single aspect, with its only window 1.2 m from the boundary. A 45 degree line from the centre of that window is crossed by the first floor element. That objection writes itself, and it is the kind of case where officers commonly negotiate a first floor set back.

Asking for a specific amendment

The objection that gets a result is rarely the one asking for refusal. Councils negotiate. An officer with a workable amendment in hand can often get it agreed with the applicant and avoid a refusal and an appeal.

So say what would resolve it. Set the first floor back by a metre from the boundary. Reduce the depth from 4 m to 3 m. Replace the flank window with a rooflight. Hip the roof rather than building to a gable. A named amendment gives the officer something to ask for.

Keep the tone measured. Objections that attack the applicant personally tend to be summarised in the officer report in a single dismissive line, and the substance gets lost with them.

Timing and who to send it to

The formal consultation period is 21 days from the date of the site notice or neighbour letter, and comments received after it will normally still be considered if they arrive before the decision is made. Do not rely on that. Submit within the period, through the council's online form so it is logged against the application reference.

If the application will be decided by officers rather than committee, which is the normal route for householder cases, ask your ward councillor whether they will request that it goes to committee. That request has its own deadline, usually tied to the consultation period, and it is the only mechanism by which a householder application gets a public hearing.

Watch for amended plans. A revised scheme triggers a further, usually shorter, consultation, and an objection to the original drawings does not automatically carry across. Ask the officer to confirm that your comments have been carried forward.

The same discipline of naming the mechanism and hitting the deadline applies to objecting to tree works in a conservation area and to asking the council to serve a section 215 notice on untidy land.

Where a larger scheme is involved, the applicant's own consultation is documented in a Statement of Community Involvement, which is worth reading to see what they told the council about your comments.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.