Crawley rewrote its householder rules in 2026
On 1 June 2026 the council adopted a new Householder Development SPD. It replaced the householder parts of three 2016 documents. Crawley puts numbers in it. Read them before you brief anybody.
Neighbours' light comes first. A single-storey addition should not cut a 45 degree line drawn from the middle of the nearest habitable room window or glazed door next door. Go up to two storeys and the line tightens to 30 degrees, drawn on plan. On a terrace, with neighbours both sides, that line often sets the depth.
Then the garden. Officers expect at least 10.5 metres of garden left between the back wall of the new room and your rear boundary, and more for a bigger house or a two-storey scheme. Behind that, two-storey rear additions should keep 21 metres between your back windows and the windows of the houses facing you. A short garden can run out of room here before the budget runs out.
Two smaller points catch people out. A pitched roof over a single-storey back room should stay below the sills of the bedroom windows above it. And a first-floor side window has to be obscure glazed and fixed shut below 1.7 metres, so plan the room so that window is never the only one.
Flat roofs, open fronts and old estate conditions
Parts of the SPD read as if written for Crawley's estates. It accepts that in parts of the town the original stores and garages were built with flat roofs, and says a flat-roofed single-storey addition may suit those streets better than a pitched one. Two-storey flat roofs are still discouraged. Where a row of houses shares matching door canopies or flat-roofed porches, the council wants them kept, and any porch should stay within a third of the house's width and 1.5 metres of the front wall.
Check the original permission too. Some estates have conditions keeping front lawns open plan, and many homes have conditions stopping the loss of parking or garages. Build over a garage or a parking bay and you may need consent even where national rules would otherwise allow the work. The council measures a parking space at 2.4 by 4.8 metres.
Flood statements and clay
The borough's flood study, prepared for Crawley and Horsham councils in 2020, singles out Langley Green, Three Bridges and Forge Wood for river flooding from the Mole and the Gatwick Stream. In June 2012 surface water flooded homes in Maidenbower, Furnace Green and Ifield Green. If the Environment Agency map shows your house in Flood Zone 2 or 3, or at surface water risk, the application needs a Flood Risk and Resilience Statement. The council's own modelling can show lower risk than the national map, so check both. Where the risk is real, new floors should sit at least 300mm above the design flood level.
Underfoot, the SPD itself says clay covers much of the borough and drains poorly, so a soakaway may not cope with rain off a new roof. Water butts and permeable paving are its suggestions. Clay also means building control will look at foundation depth, more so near trees, and the council will resist an addition built so close to a tree that it creates pressure to fell it.
How each type of extension fits Crawley
Single-storey rear. The usual first step, and no Article 4 direction in the borough takes the right away. Outside a conservation area you can add 3 metres on a terrace or semi, 4 metres detached, without an application. Prior approval stretches that to 6 or 8 metres, with the neighbours asked first.
Kitchen. Glass is where a kitchen succeeds or fails. Rooflights bring light in without adding windows that face a neighbour, which keeps you clear of the privacy distances, and a flat roof can take them where the street already has flat-roofed stores.
Open plan. Taking out the old back wall means a steel beam and pads to carry it, and on clay those pads need proper design. Crawley Building Control, the council's own service since October 2025, will check the calculations.
Two-storey. Always an application. On the side, leave at least a metre to the boundary, step back from the front and drop the ridge, or a row of semis starts to look like a terrace. On the back, the 30 degree line and the 21 metre gap usually set the depth.
Wrap-around. The side leg takes it outside permitted development, so it needs planning permission. It suits an end-of-terrace or semi with a side path, as long as that path isn't the parking a condition protects.
Side return. Most at home on the Victorian and Edwardian streets of Southgate and Three Bridges. Malthouse Road and Hazelwick Road are conservation areas, where any side extension needs permission.
Ground-floor bedroom. Attach it to the house. Council policy says a garden outbuilding should not be used as main living space. In a flood zone, a downstairs bedroom may need its floor raised further still.
Home office. A garden room must stay single storey and away from trees. An attached study shares the heating and broadband and avoids the outbuilding rules altogether.
Planning. In the 13 conservation areas, from Ifield Village to Forestfield and Shrublands, side additions and anything over one storey at the back need consent, and cladding is out. The council also asks applicants to fill in its energy and water checklist.
Cost and value. We don't print prices. Raised flood floors, deeper footings in clay and a new parking bay can each move a quote. Get three builders to see the plot.
Where these facts come from
- Crawley Householder Development SPD (adopted June 2026)
- Householder Development SPD, May 2026 text (committee papers)
- Crawley Borough Council: SPD adoption decision
- Crawley and Upper Mole Strategic Flood Risk Assessment (2020)
- GOV.UK: Permitted development rights for householders, technical guidance
- Crawley Borough Council: Article 4 directions
- Crawley Borough Council: conservation areas
- Crawley Borough Council: water neutrality
- Crawley Historic Character Assessment (2008)
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Questions people in Crawley ask
Our garage has a condition saying it must be kept for parking. Can we still extend over it?
Possibly, but you will need planning permission even for work that would normally be permitted development. The council's guide says many Crawley homes carry these conditions, so look up your estate's original permission on the planning register first.
We back onto another row of houses. How deep can a two-storey rear extension go?
Two tests apply. The new back windows should stay at least 21 metres from the windows of the houses behind, and you should keep at least 10.5 metres of garden. Angled windows can sometimes allow a little less.
We live near the Gatwick Stream in Three Bridges. Does that stop us extending?
No. Crawley's flood policy supports householder schemes where lost flood storage is made up and the new room is designed to cope. You will need a Flood Risk and Resilience Statement with the application.
Do we need to say anything about water use now water neutrality has gone?
Natural England withdrew its Sussex North position in October 2025, so you no longer have to prove water neutrality. The council still asks for efficient fittings, such as showers of no more than 8 litres a minute.