What is the 45-degree test?

A line drawn at 45 degrees from the centre of the neighbour's nearest habitable room window. If your first-floor extension crosses it, officers treat it as harming their daylight and will ask for the depth to be reduced or the extension set in from the boundary. We plot it on every two-storey scheme before submission.

Can the ground floor go deeper than the first floor?

Yes, and it usually should. A common approach is a 4 m ground floor with a 3 m first floor set 1 m in from the shared boundary, which keeps the daylight line clear while giving a full-width kitchen below.

Does the roof have to match?

Councils expect the extension roof to follow the form of the main roof, for example a hipped roof on a 1930s semi, and to sit below the existing ridge. A flat-roofed first floor is normally refused on a pitched-roof house.

How long does Guildford take to decide?

The statutory period is 8 weeks from validation for both a householder application and a Lawful Development Certificate, and 42 days for a larger home extension prior approval. Decisions can run past the statutory 8 weeks; allow 8–12 weeks.

Two-Storey Extensions in Guildford: Planning

Two-storey extensions in Guildford depend on the house. Typical homes here: Victorian and Edwardian terraces and villas around Guildford town centre and in Charlotteville; 1930s semi-detached houses in Stoughton, Burpham and Merrow. Designations to check first: Green Belt; Surrey Hills National Landscape; Conservation areas and Article 4 directions. Applications are decided by Guildford Borough Council and the Guildford Borough Local Plan: Strategy and Sites 2019 and Development Management Policies 2023.

The permitted development rules for two-storey extensions

A two-storey rear extension is permitted development only within tight limits: no more than 3 m deep, at least 7 m from the rear boundary, no higher than the existing house, eaves matching the existing eaves, materials similar in appearance, and any upper-floor side window obscure-glazed and non-opening below 1.7 m.

Most two-storey extensions exceed one of those limits, most often the 7 m rear boundary rule on London plots, so the usual route is a householder planning application. Flats have no permitted development rights.

What changes in Guildford

Extensions of more than one storey are not permitted development in a conservation area, so planning permission is always needed there.

The local constraints that most often decide the route in Guildford are listed below, taken from our Guildford area page. Each one is a reason to confirm the address on Guildford's constraints map before relying on permitted development.

Green Belt. Most of the borough outside Guildford town and the larger villages is Green Belt, including land around Shalford, Send, Ripley, East Horsley and Effingham. Source
Surrey Hills National Landscape. The Surrey Hills National Landscape (formerly the Surrey Hills Area of Outstanding Natural Beauty) covers the downs and wooded slopes south and east of the town, including land around Shalford, the Horsleys and Effingham. Source
Conservation areas and Article 4 directions. Guildford town centre, Charlotteville and Onslow Village are conservation areas, and many of the villages, including Shalford, Ripley, Send, East Horsley and Effingham, have designated centres. Source
Thames Basin Heaths Special Protection Area. The heathland around Ash and the north-west of the borough forms part of the Thames Basin Heaths Special Protection Area. Source
River Wey flood risk. The River Wey and the Wey Navigation run through Guildford town centre and on through Shalford, Send and Ripley, and land alongside them sits in Flood Zones 2 and 3. Source
Listed buildings. Guildford town centre, Shalford, Ripley, Send, the Horsleys and Effingham contain many listed houses, cottages and churches. Source

What Guildford planning officers look for

On the 1930s semis in Stoughton, Burpham and Merrow they tend to look for two-storey side extensions set back from the front wall and below the main ridge, a gap kept to the side boundary so the pair does not read as a terrace, and rear extensions that pass the 45-degree test to the neighbour's nearest habitable window. In the Green Belt and the Surrey Hills officers usually measure the extension against the original dwelling by floorspace or volume and treat outbuildings more strictly. Common refusal reasons are full-width box dormers, side extensions that create a terracing effect, and disproportionate additions on village plots. The council offers a paid pre-application service.

Fees and timelines

Guildford decides a householder application or a Lawful Development Certificate within 8 weeks of validation. The council fee is £528 for a householder application and £264 for a Lawful Development Certificate (England, from 1 April 2025; verify before applying).

Our own fee is fixed once quoted. The quote tool gives an indicative figure in minutes and a written quote follows within 24 hours.

Primary sources

The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2: the permitted development limits quoted above.
Planning Portal: do you need permission: the national guidance and the application service every council accepts.
Guildford Borough Council: planning: the council's own constraints map, validation checklist and pre-application service.

Do I need planning permission for a two-storey extension in Guildford?