Elevations and sections drawn against a real surveyed datum

What is the difference between an elevation and a section?

An elevation is the building seen straight on from outside, with no perspective: it shows what a face of the building looks like. A section is the building sliced vertically, showing floor and ceiling levels, roof pitch and wall build-ups. Elevations answer how it looks. Sections answer how tall it is.

Drawing conventions follow BS 1192 and standard London validation checklist requirements; scales and required views vary slightly between boroughs, so the local checklist governs.

Elevation or section — which is which?

An elevation is what a photograph taken from infinitely far away with an infinitely long lens would show: the face of the building, flat, with no perspective and nothing converging. That flatness is the point. It means an officer can measure directly off the drawing, and can compare your proposed rear elevation against your existing one without allowing for the angle it was drawn from.

A section is a cut. Imagine slicing the house vertically with a very large knife and standing at the cut looking in. You see the floor levels, the ceiling heights, the pitch of the roof, the depth of the foundations, and — in a building regulations section — every material layer in the walls, floors and roof.

Applicants frequently submit four elevations and no section, on the reasoning that the elevations already show the height. They show an outline height. They do not show floor-to-ceiling dimensions, they do not show the relationship between the new floor level and the existing one, and they do not show whether a person can stand up in the room you are proposing.

How many drawings does an application actually need?

The honest answer is: as many as it takes for the officer to never have to imagine anything. In practice that is four elevations existing, four proposed, and at least one section of each.

The street scene is the one worth volunteering. It shows your proposal drawn alongside the two or three houses either side, and it answers the question a case officer is actually asking — whether the thing will look out of place. On a terrace where every neighbour already has a rear extension, a street scene converts an argument into a picture.

Ground levels, datums, and why heights go wrong

London gardens slope. A rear extension that measures 2.9 metres to the eaves at the house can measure 3.3 metres at the garden end, and the permitted development limit for the eaves of a single-storey rear extension is 3 metres, absolutely, with no tolerance for the fact that your garden falls away.

This is what a datum is for. A section carries a fixed reference level — a manhole cover, a threshold, an ordnance datum height — and every height on every drawing is measured from it. Without one, each drawing is measured from whatever ground happened to be under it, and the set silently disagrees with itself.

It is also why a measured survey comes before the drawings rather than after. Levels are surveyed, not assumed, and our measured building survey establishes the datum that the whole set is then drawn against.

What changes at the building regulations stage?

The elevations barely change. The sections change completely.

A planning section is an outline: floor, ceiling, roof, height. A building regulations section is the same cut annotated with every layer — screed and insulation thicknesses, the damp-proof course and where it laps the membrane, the joist size and centres, the insulation between and below the rafters, the ventilation path, and the clear head height under any new beam.

That last one decides whether the project works. A loft conversion needs 2 metres of head height over the centre line of the stair, and the section is where you find out whether you have it before you have paid anyone to build it. Our building regulations drawings carry the annotated sections, and the structural drawings confirm the beam sizes they are drawn against.

What do elevations and sections cost in London?

Across London, 83.0% of the 77,680 householder applications decided in the twelve quarters to March 2026 were approved, and 39.0% of the 15,646 householder appeals decided by the Planning Inspectorate were allowed. Both numbers say the same thing: most householder schemes are acceptable in principle, and the ones that fail usually fail on how they were presented rather than on what they proposed.

Source: Planning Inspectorate appeals casework, decided appeals only; withdrawn, invalid and unrecorded outcomes are excluded from the denominator. Retrieved 1 September 2026. Open Government Licence v3.0.

Why do drawings fail before anyone has looked at the design?

Because validation is a completeness check, not a judgement, and it happens first. A validation officer is not deciding whether your extension is acceptable — they are confirming the application is capable of being assessed at all. A set that fails here never reaches a case officer, and the clock never starts. It is the cheapest rejection to avoid and the most annoying to receive.

Two requirements are statutory and apply everywhere in England. Every plan and drawing must be drawn to an identified scale, and every plan must show the direction of north. A drawing marked “not to scale”, or scaled to something no rule measures like 1:1.25, fails on the first. An elevation does not need a north point; a floor plan or site plan does, and omitting it is one of the most common single-item rejections.

Source: Town and Country Planning (Development Management Procedure) (England) Order 2015 (SI 2015/595), article 7(1)(c) and 7(2). Retrieved 3 September 2026. Open Government Licence v3.0. Individual boroughs publish their own local validation lists in addition to these national requirements.

When do you need a street scene elevation?

Whenever the argument is about how the building sits among its neighbours rather than what it does on its own plot. A street scene draws your house with the properties either side, at the same scale, on the same ground line — and it either wins the point or loses it in one glance. Front extensions, mansards, dormers to a front roof slope, anything raising a ridge, and almost anything in a conservation area will attract the request.

It is worth volunteering one before you are asked, for a reason that has nothing to do with compliance. Most refusals of this kind turn on a phrase like “incongruous in the streetscene”, which is a visual claim. If the only visual evidence in the file is a photograph taken by an objector, that claim goes unanswered. A drawn street scene puts your proposal in the same frame as the terrace it joins, and where the neighbours already have the thing you are proposing, it makes that fact impossible to overlook.

One caution: draw it honestly. A street scene that quietly flattens a neighbour’s ridge or omits the house that already has a mansard is worse than none, because the officer will visit the site.

Elevation and section questions