How to Prepare Drawings for a Planning Application

Start with what the planner actually needs to see

Every planning application lives or dies on how clearly it communicates a proposal to a case officer who has never set foot in your home. They will not read a long-winded covering letter before they look at the drawings — they will spread the plans on a desk (or, more likely these days, open them on a screen) and try to picture exactly what you want to build. If that picture is muddled, unclear or incomplete, you will almost certainly receive a request for further information, and in the worst cases your application will be refused at validation before anyone has even considered its merits.

The good news is that the drawings required for most householder extensions and alterations follow a fairly predictable pattern. Get the essentials right and you give yourself the best possible chance of a smooth ride through the system.

Location plans and site plans: the foundation of your submission

Nearly every application in England and Wales needs a location plan, and the planning authority has strict expectations about it. The plan should be based on up-to-date Ordnance Survey mapping, usually at a scale of 1:1250, and it must show the application site outlined with a red line. The red line should enclose the whole of the property to which the application relates, and it must be drawn tightly around the boundary — not a generous scribble that swallows half the street.

Anything else you own or control nearby may need a blue line, particularly if access, drainage or parking crosses a neighbour's land or a shared driveway. A north point is essential, however obvious the orientation feels to you.

Alongside the location plan you will usually need a site or block plan, typically at 1:500 or 1:200. This is where you show:

• The footprint of the existing house and the proposed extension
• Boundary treatments and the position of neighbouring buildings
• Access, parking and turning arrangements
• Any trees, hedges or levels that affect the design
• Distances from the proposal to the nearest neighbouring walls

This distance information matters. Case officers check it constantly against local plan policies on overlooking, overshadowing and light, so save them the trouble of measuring by marking the key dimensions clearly.

Existing and proposed plans and elevations

The core of your application is a matched set of existing and proposed drawings, usually at 1:100 or 1:50. Scale matters — 1:100 is generally acceptable for extensions, but 1:50 is preferable where the design is intricate, where a roof shape is unusual, or where you are working on a listed building.

For each state — existing and proposed — you should provide:

• Ground floor, first floor and roof plans
• All four elevations (front, rear and both sides), even if some show no change. Stating "no change" is fine, but omitting the elevation altogether is not
• At least one section drawing through the main part of the proposal, showing floor-to-ceiling heights and roof construction

Elevations should be more than bare line drawings. Note materials and finishes — facing brick, render colour, roof tile type, window frames, rainwater goods — either as annotation on the drawing or in a short accompanying schedule. Planning authorities read materials almost as closely as heights, especially in conservation areas or on streets with a strong local character. If your extension is meant to match the existing house, say so explicitly.

Make sure your drawings carry a title block with the project address, drawing title, scale, a north point, the date and a revision letter. When you submit revised plans after a case officer's comments, never overwrite the old file. Issue a new drawing number so it is obvious what has changed.

Floor plans: showing the change at a glance

A common mistake is to submit proposed floor plans using coloured shading to indicate the new extension. While colour can help, it should never be the only means of distinguishing new from existing work. Some drawings are photocopied, some are viewed in black and white, and some reviewers simply miss the tint. Use solid hatching or a clear annotation, and always label new walls and retained walls distinctly. Include the position of any removed walls and mark them "to be demolished" so the structural change is obvious.

The design and access statement

A design and access statement is formally required for major development, listed building consent, and applications involving flats or buildings open to the public. For a straightforward house extension it is often optional — but that does not mean you should skip it.

A short, well-illustrated statement can quietly answer the questions a case officer will otherwise raise. In two or three pages you can explain:

• What you are proposing and the brief behind it
• How the design responds to the street, neighbours and local character
• How scale, height and materials were chosen
• How access, parking and servicing work in practice
• Any constraints — tree roots, flood risk, listed features — and how they have been addressed

Photographs of the house, the street and the boundary are worth including, along with a few notes on the local context. Warm, plain English beats planning jargon every time.

Before you press submit, check the small things

Drawings that are accurate but sloppy still cause delays. Confirm the following before uploading:

• Everything is to a stated, consistent scale — no plans stretched to fit a sheet
• The application form, drawings and design statement all agree on dimensions and materials
• Site boundaries on the location plan match the boundary shown on the site plan
• Files are named sensibly and the PDF is legible at A3
• Any trees shown are accurately positioned, since removals and root protection areas frequently trigger conditions

Take the time to get the drawings right and the process becomes considerably more predictable. It is a small investment of effort that pays back generously the moment a case officer opens your file and understands exactly what you are proposing.