What is the difference between existing and proposed plans in London?

Why does the council need both sets?

A planning officer is not assessing your whole house. They are assessing the change: how much bigger it gets, how close it comes to next door, whether a new window looks into a neighbour's garden. The only way to see a change on paper is to put the before and the after next to each other.

Southwark's householder checklist puts it plainly: the floor plans should show the floorplan now and after the proposed changes, and the elevations should show the building's outside now and after the proposed changes. It asks for an individual floor plan for each floor of the building, so a ground-floor extension can still need the first floor drawn.

Neighbours read the pair too. When the application goes on the council's website, the person next door compares your existing and proposed rear elevations to see what they will look at from their garden. A clear pair answers their question before it becomes an objection.

Same scale, same north point, same viewpoint

Every plan and drawing must be drawn to an identified scale, and every plan must show the direction of north: that is the national rule in article 7(2) of the 2015 Order, not a local preference. For a householder set, the scale is usually 1:50 or 1:100; Richmond's local validation checklist, agreed for adoption in February 2026, asks for existing and proposed floor plans and elevations at one of those two scales.

Matching matters as much as the scale itself. Kensington and Chelsea's submission requirements, dated January 2022, ask for each existing and proposed drawing to be at the same scale, with adjoining buildings shown so that relative heights and positions are clear, and recommend placing existing and proposed elevations beside each other for ready comparison.

Viewpoint is the part people miss. If the existing rear elevation is drawn looking at the house from the garden, the proposed rear elevation must be drawn from the garden too, with the same neighbour on the same side. Southwark asks for an elevation of the front, the back and both sides, so a flank wall with no windows still gets its own existing and proposed sheet when the work changes it.

How demolition is shown on the existing drawings

Anything being removed belongs on the existing sheets, not the proposed ones, because it exists today and will not tomorrow. Kensington and Chelsea's 2022 list asks for walls or buildings to be demolished to be shown by hatching or colour, and annotation, and gives the reason in blunt terms: demolition not identified will not be authorised under any planning permission granted.

That makes the existing drawing more than a formality. If a rear wall, a chimney breast on an outside wall or an old outhouse is coming down and the drawings do not say so, the permission may not cover it. The same council asks that where a roof, a parapet or a building line is raised or extended, the line of the existing is shown as a dotted or coloured line on the proposed drawing, so the officer sees the old outline and the new one together.

Richmond goes further on bigger schemes and asks for demolition plans showing the parts of the building to be fully or partially removed. Taking out a load-bearing wall inside the house is usually a building control matter rather than a planning one; our post on the drawings for removing a load-bearing wall covers that route.

Common validation errors in existing and proposed sets

Richmond's checklist says applications that are incomplete or contain poor-quality information will be considered invalid and not processed until the missing items arrive; if the deadline it sets is missed, the application is returned and a new one has to be made. With existing and proposed drawings, the same few faults come up again and again:

A proposed sheet at a different scale from its existing partner, or a pair printed so that one is mirrored. An elevation missing because nothing visible changes on that side, when the extension still shows on it. Existing plans traced from an old brochure or a previous owner's drawings, so the proposed sheets carry the same errors. No north point, or north pointing a different way on the two sheets. A 'do not scale' note, which Richmond asks applicants to avoid. Demolition drawn on the proposed plan only, or not marked at all. Neighbouring houses left off, so the officer cannot judge the effect on them.

None of these is about design; each is a drawing that fails to match its partner or the house. If the problem is that the existing plans were wrong to begin with, our post on what to do when your drawings don't match your house sets out the fix at each stage.

Where accurate existing drawings come from

Every proposed sheet is built on top of an existing one, so an error in the existing set carries through to everything after it. That is why our planning drawings include a measured survey: the walls, openings, heights, boundaries and neighbouring windows are measured, and the existing drawings are drawn from those measurements.

For some straightforward houses part of the survey can be done from your photographs and measurements, and our post on getting planning drawings online without a site visit explains when that works and when it does not. If you already have drawings from a previous application, we check them against the house before we draw anything new on top.

What a full existing and proposed set costs

Our planning drawings start at £745, and that price covers both halves of the job: the measured survey behind the existing drawings, and the proposed drawings for every floor, elevation and roof the work changes. The chart below splits the fee and sets it beside the council's own householder fee, which you pay to the council when you apply.

The full list of sheets a householder application needs, including the location and block plans that sit alongside the existing and proposed pairs, is in our post on what drawings a householder planning application needs. If the council asks for a change once the set is in, our post on how many revisions are included in drawing fees explains what the fixed fee covers.