Balconies, verandas and raised platforms in the garden
Part 1 of the GPDO excludes verandas, balconies and raised platforms from householder rights, and defines a raised platform as one more than 300 millimetres high. Sloping gardens are where that catches people.
A raised platform in a garden needs planning permission once it stands more than 300 millimetres above the ground, because Part 1 of Schedule 2 to the General Permitted Development Order 2015 excludes verandas, balconies and raised platforms from the householder rights and then defines a raised platform by that height. The figure is in the interpretation paragraph of Part 1, it applies across the classes, and it catches far more garden decking than homeowners expect. If you are working out whether a raised platform permitted development garden project is covered, start by measuring from existing ground level to the top of the deck boards.
Why balconies and verandas are excluded from the rights
The exclusion appears in the same form in several classes. Class A, which covers extensions, Class B, which covers roof enlargements, and Class E, which covers outbuildings and incidental buildings, each say that the development is not permitted if it would include the construction or provision of a veranda, balcony or raised platform.
The reasoning is overlooking. An extension at ground level affects a neighbour's light and outlook in ways the dimensional limits control. A platform at height changes the sightlines into neighbouring gardens and windows, and no dimensional limit controls that, so the drafters took it out of the rights altogether.
That makes the exclusion absolute rather than a limit. There is no size of balcony that is permitted, and no proportion of a roof that can be used as a terrace. Either you are below the platform threshold or you need an application.
The platform height that triggers a need for permission
Part 1 defines a raised platform as a platform with a height greater than 300 millimetres. Three points follow.
Measure from the existing ground level immediately adjacent, not from a datum, and not from the lowest point if the ground falls away. On sloping gardens a deck that is level with the patio at the house end will be well above 300 millimetres at the far end, and the far end is what counts.
Measure to the walking surface. The top of the deck boards or paving, rather than the top of the joists or the top of a balustrade.
And measure as built, including any make-up layers. A deck designed at 290 millimetres and built on a sand blinding over a membrane comes out above the line.
| Garden structure | Position under Part 1 |
|---|---|
| Decking up to 300mm above ground | Generally outside the platform exclusion |
| Decking over 300mm above ground | Excluded from the rights, needs permission |
| Steps up to a door | Not normally treated as a raised platform |
| Balcony on a rear elevation | Excluded in all cases |
| Veranda or covered seating deck | Excluded in all cases |
| Flat roof of an extension used as a terrace | Excluded in all cases |
Decking, steps and garden terracing
Low-level decking laid close to the ground is usually fine, and the practical question is what happens at the edges.
Terracing a sloping garden into levels is the common trap. Cutting into the slope and retaining the upper level with a wall creates, at the lower level, a platform relative to the adjoining ground. Councils look at the finished relationship between your surface and your neighbour's ground, and a terrace that lets someone stand and look over a 1.8 metre fence is treated as a raised platform regardless of how the earthworks were described.
Steps serving a door are not generally caught, because they are a means of access rather than a platform to occupy. A landing wide enough to put a table on is a different matter, and the distinction in practice is whether the surface is somewhere you pass through or somewhere you sit.
Hard surfacing within the curtilage has its own rules about permeability and front gardens, and it does not count towards the 50 per cent coverage limit, so a patio is a simpler proposition than a deck of the same area at height.
Flat roofs used as terraces
Using the flat roof of a single-storey rear extension as a terrace needs permission, and it is one of the most commonly refused householder proposals.
The reason is straightforward. A roof terrace at first floor level looks directly into neighbouring gardens and often into neighbouring windows at a similar level, and the harm is to privacy rather than to light. Screening helps and rarely resolves it, because a screen high enough to prevent overlooking is itself a visually prominent structure on a roof.
Where a roof terrace is the client's objective, the design response that works is to pull it back from the boundary, screen the flanks with solid obstruction rather than slatted panels, and limit the depth so the usable area sits away from the party boundary. Where the house is semi-detached and the extension runs along the boundary, expect the answer to be no.
A Juliet balcony is a different case, and an arguable one. A balustrade fitted across a door opening with no platform projecting beyond the face of the wall is often treated as an alteration to the opening rather than the provision of a balcony, which brings it within the window and door rules rather than the exclusion. Our note on replacement windows and doors and when they are development sets out that boundary.
Overlooking and the neighbour position
Overlooking is a material planning consideration and loss of a view is not. Separate the two before you write anything, because conflating them weakens an otherwise good case.
Officers assess privacy by looking at the separation distance between the proposed platform and the nearest habitable room window and private garden area, the angle of view, the level difference, and any existing screening. Many authorities publish a householder design guide with indicative separation distances, and those figures are the first thing the case officer will check.
Upper floor windows carry their own obligation, and the obscure glazing requirement for side windows in Class A often appears as a condition on balcony permissions too. Our note on upper floor side windows and the obscure glazing condition explains how that is worded and enforced.
Guarding and Building Regulations issues
Planning permission is only half the exercise. A raised platform needs guarding where there is a drop, designed to the relevant Approved Document, and a balcony on a dwelling involves structural design and fire considerations as well.
Three items to raise with your building control body early: the guarding height and the gap dimensions, the structural connection where a balcony is fixed back to the building, and the fire performance of any balcony construction where the building is in a terrace or has flats above. Timber balconies on multi-occupied buildings have had a difficult decade and the detailing expectations have moved.
Access for maintenance and drainage of the platform surface are the two things the drawings usually omit.
Applying where the right does not reach
A householder application is the normal route, and it is a short exercise if the submission addresses privacy directly.
Submit existing and proposed plans and elevations, a section through the platform showing levels relative to the neighbouring ground, a sightlines drawing from the platform towards the nearest neighbouring windows and gardens, and the screening detail. A short Planning Statement setting out the separation distances against the authority's own design guidance does more than any amount of general argument about enjoying the garden.
This is general guidance, not legal advice, and only a lawful development certificate confirms formally that works are lawful. Check the position with your local planning authority or a qualified professional before relying on it.
Enter your postcode on PlanScope to see which documents your householder application is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
How high can garden decking be without planning permission?
Up to 300 millimetres above the adjacent existing ground level. Above that it is a raised platform, which Part 1 of the GPDO 2015 excludes from the householder rights. Measure to the walking surface, from the ground immediately adjacent, and remember that a level deck on a sloping garden exceeds the height at the lower end.
Is a balcony ever permitted development on a house?
No. The exclusion of verandas, balconies and raised platforms in Part 1 is absolute rather than a dimensional limit, so there is no size of balcony that is permitted. A planning application is needed in every case, and privacy is the issue the application has to answer.
Can I use the flat roof of my extension as a terrace?
Not without permission, and these proposals are commonly refused. A first floor terrace looks into neighbouring gardens and windows at a similar level, which is a privacy harm that screening rarely resolves. Pulling the usable area well back from the boundary and using solid flank screening gives the best prospect.
Does a Juliet balcony need permission?
It is arguable. A balustrade across a door opening with no platform projecting beyond the face of the wall is often treated as an alteration to the opening rather than the provision of a balcony, which brings it within the window and door rules. Where it matters, apply for a lawful development certificate rather than assuming.
What about guarding and Building Regulations?
Planning permission does not cover construction. A raised platform with a drop needs guarding designed to the relevant Approved Document, and a balcony needs structural design and fire consideration, particularly where the building is in a terrace or has flats above. Raise guarding heights, fixings and fire performance with building control early.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.