Planning permission for a new house in a back garden

A new house in a back garden is a full application in its own right, never a householder one, and backland development planning permission usually turns on four questions the case officer asks in the first ten minutes. Can the plot be reached safely. Does the new house harm the amenity of the homes wrapped around it. Does the subdivision read as part of the area's grain. Do the boundary trees survive the layout. Answer those four with drawings rather than assertions and a single garden plot becomes one of the more straightforward minor applications. Get the access wrong and the rest of the pack cannot rescue it.

Where garden land sits in policy

Residential gardens are not previously developed land. The Framework's glossary has excluded them since 2012, so a garden plot attracts none of the policy support that a brownfield site does, and the presumption in favour of sustainable development is doing far less work for you than you might hope. Check the glossary wording in the current edition of the NPPF, published on 17 August 2026 and arranged by policy code rather than paragraph number.

What matters far more is the adopted local plan. Most authorities carry a design or residential development policy that deals directly with infill, backland and garden land, often with a clause about respecting the established pattern of development and the spacing between buildings. Some carry a specific garden land policy written after the 2010 change. Read it before you draw anything, because the wording tells you which of the four questions your council treats as the deal-breaker.

Two other checks belong at this stage. The site is a new planning unit created by subdividing a curtilage, which is development under section 55 of the Town and Country Planning Act 1990, and you will need the right ownership certificate if any part of the access strip belongs to someone else. And if the plot sits in Flood Zone 2 or 3, the sequential test arrives before the design discussion, not after it.

Access, turning and the bin question

Access kills more backland schemes than design does. The new house needs a route from the highway that satisfies the local highway authority on visibility, width and gradient, and that route almost always runs alongside the host dwelling.

The practical tests are these. Visibility splays measured from the back of footway in both directions, to the standard in the council's own design guide. A drive wide enough for a car to pass a pedestrian, usually taken as around three metres over the first stretch and wider where two vehicles must pass. Enough space on the plot to turn, so that a car leaves in forward gear rather than reversing onto the carriageway. Manual for Streets is the national reference most highway officers reach for, and it is worth quoting the relevant paragraph in your covering statement rather than leaving the officer to find it.

Refuse collection is the detail that catches self-builders out. Councils set a maximum distance residents can be expected to drag a bin to the collection point, and a maximum reversing distance for the refuse vehicle, both in a local waste and design guide rather than in national policy. Find those two numbers, put a collection point on the site plan, and show the drag distance as a dimension. An officer who has to ask for that drawing has already started writing a holding objection.

Overlooking, privacy and the amenity case

Backland plots are surrounded on three or four sides by other people's gardens, so the amenity assessment is unusually exposed. Many councils' design guides use a back-to-back separation of about 21 metres between facing habitable room windows and around 12 metres between a habitable window and a blank flank wall or boundary. These are local rules of thumb rather than national standards, and the officer will apply the version in their own supplementary planning document.

Design out the problem instead of arguing about it. Single storey or one and a half storeys with rooflights on the sensitive elevation. First floor windows serving bathrooms or landings, obscure glazed and fixed shut below 1.7 metres, secured by condition. Blank flank walls where the separation is tight. Balconies and terraces facing the plot's own garden, never a neighbour's.

Overshadowing is the other half of the case. On a tight plot it is worth running a simple shadow study at the equinox and midsummer, and if the geometry is awkward, a formal daylight and sunlight assessment against the BRE guidance carries far more weight with a committee than a paragraph of reassurance.

Trees, roots and the layout that follows

Boundary trees in mature suburbs are frequently protected, either by a Tree Preservation Order or by conservation area status, and they will shape the footprint before the architect does. Commission a BS 5837 tree survey early, because the root protection area for a single-stem tree is calculated as twelve times the stem diameter, and on a small plot that circle can swallow the parking court you were relying on.

The sequence matters. Survey first, then the tree constraints plan, then the layout, then the arboricultural impact assessment and method statement. Doing it the other way round produces a design that needs the tree removed, and removal of a protected tree to enable development is a poor start with the tree officer.

Check the drainage runs and the driveway construction against the same constraint. No-dig surfacing within a root protection area is normal practice and needs to appear on the drawings as well as in the text.

The tandem development objection

Tandem development is the standard objection to a house directly behind another, sharing a single access past the flank of the front dwelling. The harm alleged is disturbance to the host dwelling from vehicles passing its windows and garden, a cramped relationship between the two properties, and a form of development at odds with the street's established rhythm. Inspectors have treated it as a genuine planning issue for decades, so it is worth meeting head on.

The answers that work are physical. Separate the access from the host dwelling's main garden with a wall or a change in level. Keep the drive away from habitable windows where the geometry allows. Give the new house its own garden of a size comparable to others nearby rather than a token strip. Show the plot depths and garden areas of neighbouring properties on a context plan, so the officer can see for themselves that the proposal sits inside the local range.

Character is judged on what is visible. If the plot is well screened and the street scene barely changes, say so and prove it with a long section and a view from the pavement.

Levels, drainage and boundaries

Garden plots often sit lower than the road, which turns surface water into a design problem rather than a paperwork one. Set out existing and proposed levels, the finished floor level, and how run-off is dealt with on site. Infiltration testing to BRE Digest 365 tells you whether a soakaway works before you commit to one, and where infiltration fails you need an attenuated connection agreed in principle with the sewerage undertaker. On a single dwelling a proportionate drainage strategy is usually enough, and the lead local flood authority will only be consulted on larger schemes.

Boundary treatment is worth a drawing of its own. Close boarded fencing at 1.8 metres on three sides is what most applicants propose and what most neighbours dislike. Hedging retained and reinforced, with fencing behind it, reads better and helps the ecology case.

The evidence base for one plot

Biodiversity net gain applies to a single new dwelling unless an exemption bites. The two that matter here are the de minimis exemption, where the development affects less than 25 m² of on-site habitat and no priority habitat, and the self-build and custom build exemption for schemes of no more than nine dwellings on a site under 0.5 hectares. If neither applies, a biodiversity net gain assessment and a biodiversity gain plan are unavoidable, and the metric baseline has to be taken before you clear the plot.

A workable pack for a single backland dwelling is a site location plan, existing and proposed site plans with levels, floor plans and elevations, a street scene or context elevation, the tree survey and constraints plan, the drainage and levels information, ecology and the metric where required, and a Planning Statement that answers access, amenity, character and trees in that order. A Design and Access Statement is only mandatory for certain applications, but on a contested plot it is the document that carries the design argument.

One honest uncertainty. Whether a plot reads as acceptable infill or as cramped backland is a matter of planning judgement, and two officers can reach different views on the same drawings. Pre-application advice costs little relative to a refusal and a nine-month delay, and it is the only way to test that judgement before you spend money on surveys.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Enter your postcode on PlanScope to see which reports a garden plot is likely to need.