What the council's 2023 house guide asks for
Coventry City Council adopted a new Householder Design Guide on 11 April 2023, replacing the version from 2003. Planning officers check every householder application against it, so a designer who hasn't read it is guessing. It runs to ten principles. The ones that shape most Coventry extensions sit under rear and side.
For a single-storey rear addition the guide gives two tests. Either it stays within 4m along the boundary, or it stays inside a line drawn at 45 degrees from the centre of the neighbour's nearest habitable rear window, whichever allows more depth. Ground levels and which way the gardens face can change the answer. A two-storey addition gets the 45 degree test only, measured from the neighbour's nearest rear window on either floor, plus 20m between facing rear windows and usually 10m from first-floor windows to the back boundary.
Side extensions should be subservient with a lower ridge. At first floor the guide wants the wall pulled in 0.5m from the side boundary and set back 1m from the front of the house, so that pairs of semis don't join up into a terrace. On a corner plot keep at least 2m between the extension and the boundary at its narrowest point. Match the bricks for colour, size and bond, and match the mortar joints too.
Two things the guide is cool on. Balconies off a rear extension are rarely accepted, because of overlooking. Front extensions that push past the established building line generally aren't either.
Fitting each type to a Coventry house
Ordered by how often each comes up here, with a full guide behind every one.
Single-storey rear. Outside a conservation area, a semi or terrace can usually go 3m beyond the original back wall without an application, or 4m on a detached house. The prior approval route allows 6m or 8m, but the neighbours get a say and the council has 42 days to respond.
Kitchen. The council's guide wants rooflights flush and on rear slopes. Over a new kitchen that tends to suit anyway, since daylight from above doesn't put a window facing next door.
Side return. Where a Victorian terrace has a long outrigger and only a narrow passage to the fence, the guide says infilling is not normally appropriate unless the 25 degree test is met. Otherwise it prefers you lengthen the outrigger.
Open plan. Knocking the old back wall through needs a beam sized by an engineer and approved by the council's own building control team. On sulphate-bearing mudstone the foundation concrete may need a resistant mix as well.
Two-storey. Common over the side drive of an interwar semi. Plan for the 1m front set-back and 0.5m side gap at first floor, a lower ridge, and a full application.
Wrap-around. The side leg takes it outside permitted development, so it always needs planning. Keep a gap to the boundary where you can, as the guide asks, for bins and access to the back.
Downstairs bedroom. A bedroom and shower room at the back lets an older relative stay at home. It must be part of the house, though. The guide doesn't let a garden outbuilding be used as living accommodation.
Home office. An attached room is easier to heat and get broadband to. A cabin in the garden has to stay incidental to the house under the council's guide, and can't be run as a business.
Planning. In all 19 conservation areas, a side extension, cladding or a rear extension of more than one storey needs an application. Elsewhere, check that the original estate consent didn't remove your rights.
Cost and value. We don't publish prices. Deep foundations near trees, made ground in the inner city and matched brick in a conservation area all push a quote up. Get three builders round to see the house itself.
Brook valleys, mudstone and protected trees
Coventry's flood risk follows its brooks. The council's 2022 flood summary puts homes in Flood Zones 2 and 3 along the Sherbourne and Pickford Brook, in parts of Allesley, Coundon and Spon End, beside the Sowe around Holbrooks and Wyken, and along Canley Brook west of the Fletchamstead Highway. If your house is in one of those zones, the application needs a flood risk assessment. The Environment Agency's standing advice for minor extensions sets out what it should cover, including floor levels. Surface water is a separate problem, and the same summary says a large number of properties in Cheylesmore and Stivichall are at risk.
Underneath, the British Geological Survey describes the Mercia Mudstone as a heavily overconsolidated clay, with gypsum that can give high sulphate levels and attack ordinary concrete. Much of the city has boulder clay on top. The inner city sits on made ground several metres thick in places, and there may be old shallow coal workings along the eastern edge of the coalfield. None of that stops an extension. It does mean the inspector wants to see the trench before it is filled.
Trees matter too. The council says about 5,000 trees in the city are covered by more than 500 preservation orders. A protected tree near the new footings can change the foundation design, so look at the online planning map and email the tree officer if you're unsure.
Earlsdon, Brownshill Green and the other conservation areas
Earlsdon and Brownshill Green became conservation areas in November 2022. Since then a side extension there needs planning permission, as it is in Chapelfields, Stoke Green, Kenilworth Road and the rest. Both areas also carry Article 4 directions, made in March 2022. The council publishes the wording on its Article 4 page. Read it, or ask the conservation team, before you assume a single-storey rear addition is still allowed.
On the city's rural edge some houses fall in the Green Belt. National policy allows extensions there only if they aren't disproportionate to the original building, and earlier additions count against you. The planning register shows what neighbouring owners have been given, which is the best guide you'll find.
Where these facts come from
- Coventry City Council: Householder Design Guide SPD (2023)
- Coventry City Council: Householder Design Guide adoption statement
- Coventry City Council: Article 4 directions
- Coventry City Council: list of conservation areas
- Coventry City Council: summary of flood risk (October 2022)
- Coventry City Council: tree preservation orders
- Coventry City Council: online planning register
- British Geological Survey: geology of the Coventry area (WA/89/29)
- GOV.UK: householder permitted development technical guidance
- Environment Agency: flood risk standing advice
- GOV.UK: NPPF, protecting Green Belt land
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Questions people in Coventry ask
My neighbour's kitchen window is close to our boundary. How far back can I go?
Under Coventry's 2023 guide a single-storey rear extension should stay within 4m along the boundary or inside the 45 degree line from the centre of their nearest habitable rear window, whichever allows more. The planner will also look at ground levels and which way the gardens face.
We're on a corner plot. Can we build out to the side?
Possibly. The guide asks for a width in proportion to the original house and at least 2m between the extension and the boundary at its narrowest point.
Our house backs onto Canley Brook. Does that change anything?
Check the flood map first. Parts of the Canley Brook corridor are in Flood Zones 2 and 3, and an extension there needs a flood risk assessment with the application. The Environment Agency's standing advice says what to put in it.
Can we turn the garden room into a granny flat?
Not as a separate home. Coventry's guide says garden buildings must stay incidental to the house and can't be used as living accommodation. A ground-floor extension attached to the house is the usual answer.