The permitted development rules for loft conversions
A loft conversion with a rear dormer is permitted development on a house if the added roof volume is no more than 40 m³ on a terraced house or 50 m³ on a semi-detached or detached house, the dormer sits at least 200 mm back from the eaves and no higher than the ridge, there is no dormer on the roof slope facing the road, materials are similar in appearance, and side windows are obscure-glazed.
Flats and maisonettes have no permitted development rights, so a loft to a top-floor flat always needs planning permission. Full-width box dormers that reach the ridge, and hip-to-gable conversions on semis whose volume exceeds 50 m³, also fall outside the allowance.
What changes in Broxbourne
Roof extensions are not permitted development in a conservation area, so a dormer or hip-to-gable there needs a householder planning application designed to the area's appraisal.
The local constraints that most often decide the route in Broxbourne are listed below, taken from our Broxbourne area page. Each one is a reason to confirm the address on Broxbourne's constraints map before relying on permitted development.
- Green Belt. Land west of the A10, including Goffs Oak and the countryside around Cheshunt and Hoddesdon, is Green Belt, along with much of the Lee Valley to the east. Extensions to houses in the Green Belt must not be disproportionate to the original dwelling, and outbuildings face a strict test on size and siting. Check the council's constraints map for the boundary at your address. Source
- Lee Valley Regional Park and River Lea flood risk. The Lee Valley Regional Park runs the length of the borough east of the railway, and land alongside the River Lea, the Lee Navigation and the reservoirs sits in Flood Zones 2 and 3. Ground-floor extensions and basements there may need a flood risk statement with the application, and houses backing onto the park can face additional landscape and ecology requirements. Source
- Conservation areas. Broxbourne's conservation areas include Hoddesdon town centre, Broxbourne, Wormley and parts of Cheshunt, with others in the villages. Roof extensions are not permitted development inside them, and officers apply the character appraisal to extensions and dormers. Check the council's constraints map for the exact boundaries before relying on permitted development. Source
- Article 4 direction on HMOs. We understand the Borough of Broxbourne has used an Article 4 direction to remove permitted development for converting a house into a small house in multiple occupation (C3 to C4), so HMO conversions normally need planning permission. Check the constraints map for the current extent of the direction. Source
- Listed buildings. Hoddesdon High Street, Broxbourne, Wormley and the older parts of Cheshunt and Waltham Cross contain listed houses, inns and churches, including the Eleanor Cross at Waltham Cross. Listed building consent is needed for almost any alteration, internal or external. Source
What Broxbourne planning officers look for
Broxbourne officers assess householder applications against the Broxbourne Local Plan 2018–2033 and the council's supplementary guidance on residential extensions. On the 1930s and post-war semis that dominate Cheshunt and Hoddesdon 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, rear extensions that pass the 45-degree test to the neighbour's nearest habitable window, and hipped roofs kept where a gable would unbalance the pair. In Goffs Oak and other Green Belt areas they check the extension against the original house and resist large outbuildings. Common refusal reasons are full-width box dormers, side extensions that create a terracing effect, and disproportionate Green Belt extensions. Outside conservation areas, hip-to-gable and rear-dormer lofts within 50 m³ on a semi are routinely lawful and we secure a Lawful Development Certificate as proof. Broxbourne offers a paid pre-application service. Decisions can run past the statutory 8 weeks; allow 8–12 weeks.
Fees and timelines
The council fee for a householder application is £528 and for a Lawful Development Certificate £264 (England, from 1 April 2025; verify before applying). Both are decided within 8 weeks of validation.
Our own fee for the drawings and the application is fixed once quoted and depends on the project type, its size and the constraints above. Answer six questions in the quote tool and we email you an indicative figure within minutes, then a written fixed-fee quote within 24 hours.
