Adding a second storey to a bungalow

A bungalow first floor extension is one of the few householder projects with a genuine permitted development route and a high refusal rate when it goes to a full application. Both facts come from the same place. Class AA of Part 1 of Schedule 2 to the GPDO 2015 allows one additional storey on a single-storey house, subject to prior approval and a long list of limitations. Where the house or the street does not qualify, the planning argument becomes a question about the character of a uniform single-storey street, and that argument is often lost.

Work out which route applies before you pay anyone to draw anything.

The permitted development route and its limits

Class AA permits the enlargement of a house by adding storeys, with one storey allowed where the existing house has a single storey. It is a prior approval right, so you still apply to the council. What the council may consider is restricted to the matters the Order lists rather than to the whole planning merits.

The limitations that most often rule a bungalow out:

• the house must have been built between 1 July 1948 and 28 October 2018
• it must be detached, semi-detached or terraced, and not a flat or a maisonette
• it must not be listed, and must not be in a conservation area, National Park, National Landscape, World Heritage Site, the Broads or on a site of special scientific interest
• the new storey must sit on the principal part of the house, not on a rear addition
• no storeys may have been added to the house before
• the floor to ceiling height of the new storey is capped, and so is the increase in roof height and the overall height of the finished house
• no windows are permitted in any wall or roof slope forming a side elevation
• engineering works are limited to strengthening the existing walls and foundations

The height limits differ according to how many storeys are added, and they are drafted tightly. Read Class AA itself, or the government's technical guidance for householders, rather than working from a summary. The side elevation window restriction catches a lot of designs, because a first floor laid out around a central landing usually wants a side window for the stair.

Prior approval also requires you to submit material on the impact on neighbours' amenity, including daylight and sunlight. That is not a box-ticking exercise on a tight plot.

Where the house was built before July 1948, or sits in a conservation area, or has already been extended upwards, the permitted development route is closed and you are making a full householder application.

Why bungalow streets attract refusals

Bungalow estates were usually built in one go, to one house type, with a consistent eaves line and a long uninterrupted roofscape. Adding a storey to one house in that street doubles its height and leaves it standing alone.

Officers refuse these for three recurring reasons. Harm to the character and appearance of the street, where the uniform single-storey roofline is identified in the local plan or a design guide as a feature worth keeping. Loss of light or outlook to the bungalows either side, which sit low and close. And overlooking, because a first floor window in a street of bungalows looks down on gardens that have never been overlooked.

The honest position is that in a wholly unaltered bungalow street, an early application to go up is hard to win and the fifth is straightforward. Policy on character does not operate retrospectively, so precedent in the street is the strongest single factor in your favour.

Which is why the survey of the street comes before the design.

Evidence on street character and scale

Walk the street and the two streets either side with a camera and a notebook. Record every house that has been altered above eaves level: a full second storey, a raised ridge, a large rear dormer, a loft conversion with roof lights to the front.

Then build the evidence into three items:

1. A street elevation drawing showing your house and its neighbours either side at the same scale, existing and proposed
2. A location plan marking every property within the immediate context that has been altered above eaves level, with the planning reference where you can find it on the council's register
3. Photographs from the opposite footway showing the roofline as built

The street elevation is the drawing that decides the application. An officer looking at a proposal that sits below the ridge of a neighbouring two-storey house, or that matches an already-altered neighbour, has a different conversation from one looking at a single tall house in a flat run.

Where several houses in the street have already gone up, say so in plain terms in the Planning Statement with the references listed. Where none have, be realistic about the odds and consider the alternatives in the next section but one.

Daylight and the neighbours either side

Bungalows sit low. A new first floor on the house next door can take light from a kitchen window or a conservatory in a way that the same extension on a two-storey house would not.

Two tests do most of the work. The 45 degree test, applied on plan and in elevation from the centre of the neighbour's nearest window, is the one most councils use for householder applications and most design guides illustrate. The 25 degree test from the centre of the neighbour's window, taken in section, checks whether the new massing breaches a line drawn upwards from the window.

Three practical moves reduce the problem. Set the new storey back from the flank wall nearest the neighbour, so the mass is pulled away from their window. Use a hipped roof rather than a gable on the side facing the closest neighbour, which drops the bulk at the point it matters. And keep the ridge as low as the floor to ceiling heights allow.

Overlooking is answered by window position rather than by glazing treatment. Design the new storey so habitable rooms look front and rear, with bathrooms and the stair on the flanks. Where a flank window is unavoidable, expect a condition requiring obscure glazing and a restricted opening, and our note on obscure glazing conditions on side facing windows covers how those conditions are worded and enforced.

Can the existing walls take it

This is the question that changes the budget rather than the permission, and it is worth answering early.

Bungalows of the 1950s and 1960s commonly sit on shallow strip foundations sized for a single storey and a light roof. A new storey adds load that those foundations may not have been designed for, and the answer is often underpinning or a new internal frame carrying the new floor down to new pads.

Three things a structural engineer will look at: the foundation depth and width, exposed in a trial hole rather than assumed; the wall construction, since a single-skin or a thin cavity with poor ties behaves differently from a modern cavity wall; and the existing ground floor, which may need strengthening if it becomes a transfer structure.

Under the permitted development route, engineering operations are limited to strengthening what is there. If the structural answer is a new frame or a substantial rebuild, Class AA may no longer cover the work, which pushes the project into a full application. Get the structural view before you commit to the prior approval route.

Design approaches that get consent

Four approaches come up repeatedly, roughly in order of how easily they are accepted.

A storey set within a new roof rather than added above the existing eaves, using rooms in the roof with dormers, which raises the ridge without creating a two-storey elevation. This is often the better answer in a uniform street, and it overlaps with the ground covered in raising the ridge height on a bungalow.

A partial first floor over part of the footprint only, set back from the front elevation, so the single-storey frontage reads from the street.

A full storey with a hipped roof matching the pitch and the eaves detail of the original, which works where the street has a mixed roofscape already.

A contemporary storey in a different material, lighter in weight and clearly a later addition. This succeeds in some authorities and fails in others, and it needs a design officer on side.

Rear dormers are the usual fallback where a full storey is refused, and the rules for them are set out in rear dormers on a semi detached house.

What to submit

For a full householder application: existing and proposed floor plans, existing and proposed elevations, a street elevation with neighbours at the same scale, a section through the house and the nearest neighbour showing the daylight angles, a site and location plan, and a short planning statement covering character, light, overlooking and any precedent in the street.

For prior approval under Class AA: the plans and elevations, the information the Order requires about the proposed development, and the material on neighbour amenity including daylight and sunlight. Councils have eight weeks, and if they do not determine it in time the development may proceed, so get the submission complete.

Either way, the drawing to get right is the street elevation. Enter your postcode on PlanScope to see which supporting documents your site is likely to need.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it, and remember that a lawful development certificate is the formal way to confirm that works are lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.