Red line and blue line boundaries on a planning application
The red line defines the application. It is the single most misunderstood mark on a planning drawing, and drawing it wrongly is the most common reason a location plan is sent back.
Last reviewed 1 August 2026. General guidance for England, Scotland and Wales — your council’s own requirements take precedence.
What the red line encloses
The red line goes around everything the application relates to — not just the building being altered. In practice it normally includes:
- The building or structure the proposal concerns
- The part of the garden, yard or curtilage affected by the proposal
- Any land needed to carry out the proposal, such as a new parking or turning area
- The access from the site to a public highway
The access to the highway — the mistake that costs the most time
If your site does not directly adjoin a public road, the red line must normally extend along the driveway, track or private lane that connects it to one. A site drawn as an island with no route to the highway leaves the council unable to assess access, and the plan comes back.
This catches out sites behind other properties, farm and rural sites reached by a track, and flats or units reached across shared land. If you are unsure whether the road at the end of your drive is adopted, the council’s highways team can tell you.
When you need a blue line
A blue line marks other land in the same ownership or control that is adjacent to or near the application site but is not part of the application.
Its purpose is to show the council the full extent of what you control nearby, so they can see whether the proposal is a fragment of something larger. If you own only the application site and nothing adjoining it, no blue line is needed.
Red and blue must not overlap. Land is either in the application or it is not.
The red line is not your title boundary
This distinction matters and is frequently missed. Ordnance Survey mapping shows physical features — walls, fences, kerbs, building outlines — surveyed on the ground. It does not show legal ownership.
A red line drawn on OS mapping describes the extent of your application. It is not evidence of what you own, it does not determine a boundary dispute, and it does not change your title. Legal boundaries are a matter for the title plan registered at HM Land Registry and, ultimately, the deeds.
The two often coincide, which is why the difference is easy to overlook. Where they do not — a fence built in the wrong place years ago, for example — the physical feature on the map is what is surveyed, and the red line you draw is what you are declaring.
Ownership certificates follow the red line
Planning application forms include an ownership certificate, and which one you sign is determined by who owns the land inside the red line.
Broadly: you certify that you own all of it, or that you have given notice to those who own part of it, or that you have taken steps to identify owners you could not trace. Extending a red line over a neighbour’s land — often the access track — therefore creates a notice obligation people do not expect.
That is a legal declaration rather than a drawing question, and getting it wrong can invalidate a permission later. If ownership inside the red line is not entirely yours, take advice before signing.
Common questions
Does the red line have to follow my fence exactly?
It should follow the extent of the land your application covers, which usually follows physical boundaries because that is what is on the map. It does not have to match your title plan, and it is not a statement about ownership — it is a statement about what the application relates to.
What colour and thickness should the lines be?
Solid red for the application site and solid blue for other land in the same ownership are the near-universal convention. Some authorities specify a line weight or ask that the red line be unbroken. The convention matters more than the exact shade — a dashed or faint line invites a query.
My driveway crosses a neighbour’s land. What do I do?
If the proposal depends on that access, it normally needs to be inside the red line, which means the ownership certificate on your application form changes and notice may need to be served on the owner. This is worth getting right before submission rather than after.
Can the red line cover more than one parcel?
Yes. An application site can include several parcels, and the red line can enclose them as one area or as separate areas on the same plan. What matters is that the total enclosed area is exactly what the application covers.
Need the plans themselves?
We draw location and block plans on current, licensed Ordnance Survey mapping at a true stated scale, with your red line boundary, north arrow, scale bar and our OS licence number. Draw the boundary yourself and see the price before you buy.
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