Reports for a two-storey side extension on a semi

A two-storey side extension on a semi always needs planning permission, because permitted development under Class A allows a side extension of one storey only. The documents for a two-storey extension are the standard householder set: forms, certificates, a location plan, a site plan, existing and proposed floor plans and elevations, and the fee. What changes with the second storey is the amenity evidence, because a first-floor flank wall close to a boundary is the single most common reason householder extensions get refused.

What a householder application must contain

The national requirements are short. Everything else comes from your council's local validation list.

• The completed householder application form and the correct ownership certificate.
• A location plan at 1:1250 or 1:2500 with the application site edged red and any other land in the same ownership edged blue.
• A site or block plan, usually at 1:200 or 1:500, showing the extension, boundaries and any trees.
• Existing and proposed floor plans and elevations at a standard metric scale, with a scale bar and a north point.
• The application fee. Householder fees are indexed annually, so use the current schedule on the Planning Portal fee calculator rather than a figure quoted in an older article.
• The CIL additional information form, which most authorities require even where no levy is payable.

A Design and Access Statement is not required for an ordinary householder application. Article 9 of the Development Management Procedure Order 2015 requires one for major development, for listed building consent, and for development in a conservation area or World Heritage Site that creates a dwelling or 100 m² or more of floorspace. Outside those cases a short Design and Access Statement is still worth writing, because it is the only place you get to explain the design choices in your own words.

Why a two-storey flank wall changes the evidence

Ground-floor extensions are judged mostly on depth and on the boundary relationship. Add a storey and three further issues appear.

The first is the terracing effect. Most householder design guides ask for a set-in of at least one metre from the side boundary at first-floor level, and a set-back of one to two metres from the front elevation, so that the pair of semis still reads as a pair rather than as a continuous terrace. Councils apply this firmly and it is written into the design guides rather than into national policy. Our note on what officers check in a householder design guide SPD sets out how much weight those documents carry.

The second is loss of light and outlook to the neighbour. The rule of thumb most officers reach for first is the 45-degree line taken in plan and in section from the nearest neighbouring habitable-room window, and it is a screening test rather than a standard. We have written separately on how officers apply the 45-degree rule.

The third is overlooking. A first-floor side window facing a neighbouring garden invites a condition requiring obscure glazing to a stated level and fixed opening below 1.7 metres above floor level. Draw the window as obscure-glazed from the start and the condition becomes unremarkable.

When a daylight and sunlight assessment earns its fee

Most two-storey side extensions do not need one. Commission a Daylight and Sunlight Assessment when one of these is true.

The neighbouring window closest to the extension serves a habitable room, sits within about three metres of the boundary, and the extension breaches the 45-degree line in section. Or the neighbour has already objected on light grounds and the case is going to committee. Or the local design guide sets a numeric standard that your scheme fails and you want to show the actual effect rather than the geometric shortcut.

The assessment applies the BRE guidance on site layout planning for daylight and sunlight, which works through vertical sky component at the window face, the no-sky line inside the room and annual probable sunlight hours where the window faces within 90 degrees of due south. It is a modelling exercise using measured survey data, and the result is only as good as the inputs. Fees are meaningfully lower if you supply an accurate measured survey rather than asking the consultant to arrange one.

An honest word about this. A daylight assessment does not win a refusal-bound scheme. It converts an argument about a line on a drawing into an argument about numbers, which helps when the numbers are on your side and does not help when they are not.

Trees, drains and the extras councils ask for

Side extensions dig foundations close to boundaries, so two other consultees appear.

If a protected tree or a tree in a conservation area sits within about 12 times its stem diameter of the works, expect a request for an arboricultural report to BS 5837:2012 showing the root protection area and the foundation solution. Councils rarely ask for this on a rear extension and often ask for it on a side extension, because the side of a plot is where street trees and boundary trees live.

If the extension crosses a public sewer or sits within three metres of one, you need a build-over agreement from the water and sewerage undertaker. That is a separate consent from planning permission and it is not a validation requirement, but it holds up construction if you leave it until the foundations are dug.

Where the semi sits in a conservation area or is listed, the pack grows again: a heritage statement, a materials schedule, and for a listed building a separate listed building consent application with its own drawings.

An illustrative pack for a 1930s semi

Illustrative example. A two-storey side extension on a 1930s semi in an unconstrained suburban street, with the neighbour's ground-floor kitchen window 1.5 metres from the shared boundary and a rear garden of ordinary depth.

1. Householder application form, Certificate A, and the CIL additional information form.
2. Location plan at 1:1250 and a block plan at 1:200 showing the one-metre set-in and the boundary.
3. Existing and proposed plans and elevations at 1:100, plus a street elevation at 1:100 showing both semis so the officer can see the pair.
4. A short design and access statement of one or two pages covering the set-in, the set-back, the roof form and the materials to match.
5. A 45-degree diagram in plan and section from the neighbour's kitchen window, drawn to scale.
6. A daylight and sunlight assessment only if that diagram shows a breach.

That pack validates in most English authorities. It is not a promise about the decision.

Checking the local validation list before you submit

Every council publishes a local validation list, and they differ more than people expect: some require a parking and access statement for any extension adding a bedroom, some require a biodiversity checklist on all applications, some want photographs of the existing building.

Download the list for your authority, read the householder section, and tick each item against your drawings. Fifteen minutes there saves the three weeks that an invalid application loses while the paperwork goes back and forth.

Enter your postcode on PlanScope to see which reports your site is likely to need before you draw anything. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance rather than legal advice, so check the position with your local planning authority or a qualified professional before relying on it.