What the Northampton design guide asks for
Northampton has its own householder rulebook. The Residential Extensions and Alterations Design Guide was adopted by the old borough in December 2011, and West Northamptonshire Council still lists it and still quotes it in planning reports. Two lines from it come up again and again. An addition should respect the form and design of the house it is joined to, and it should normally stay subservient to it.
The numbers live in Appendix 6. Officers quote a recommended minimum of 21 metres between the rear walls of facing houses, and 13 metres from the side of one house to the back or front of the next. Those distances matter most when you build upwards. A ground floor kitchen rarely troubles them. A bedroom above it can.
Reports also talk about a 45 degree test for a neighbour's nearest window, and about the gaps between detached houses. Close a gap with a two-storey side addition and the street can start to look terraced, which is where refusals tend to come from.
Ten ways to add room to a Northampton house
Single-storey rear. The default for an interwar semi or a post-war estate house. Permitted development allows 3 metres from the original back wall, or 4 metres if detached, up to 4 metres high. Notify the council first and outside a conservation area that rises to 6 or 8 metres.
Side return. Made for the Victorian terraces off Kettering Road and Wellingborough Road, where a narrow yard runs beside the back wing. In the Boot and Shoe Quarter it counts as a side addition, so it needs an application.
Kitchen. On a shoe-trade terrace the kitchen usually sits in the back wing, dark and narrow. Glass in the roof of a new side or rear section does more for it than a few extra square metres of floor.
Wrap-around. Joining a side return and a rear addition in one L gives a terrace its biggest ground floor. In a conservation area the side leg alone means a planning application, and the two together are judged as one scheme.
Open plan. Knocking the old back wall through needs a steel beam and something firm under each end. On the Victorian grid that is often a party wall shared with next door, so the Party Wall Act notices go out early.
Two storey. Permitted development stops at 3 metres deep and 7 metres clear of the back boundary, and allows none in a conservation area. Most Northampton plots mean an application, measured against the 21 and 13 metre distances above.
Downstairs bedroom. Where a semi or estate house has space at the side, a bedroom and shower room on one level lets someone stay put when the stairs get hard. Keep thresholds level from the start.
Home office. An attached office borrows the house's heating and broadband. Some terrace yards still have an old outworkers' workshop worth surveying first.
Planning. Check the conservation area map, the flood map and the planning register for your street, in that order. Anything taller than a single storey should be tested against the 2011 guide before you appoint anyone.
Cost. No figure here. Floor levels raised for flood risk, deeper footings on old quarry ground and the size of the steel move a Northampton quote more than the room size does. Ask three builders to price one set of drawings.
Brooks, the Nene and old ironstone pits
Flooding shapes more extensions here than people expect. The Environment Agency runs a warning area for land near the Dallington Brook and the Brampton Branch, naming Shankley Way, Baring Road, Newcombe Road, Swansea Road, Swansea Crescent and Dallington Green. A wider one covers low-lying ground beside the Nene and its tributaries through the town.
A warning area is not a flood zone, so check your address on the government flood map. If it falls in Zone 2 or 3 and the work needs an application, a flood risk assessment goes in with it. The standing advice for minor extensions asks for floors at least 600 millimetres above the estimated flood level, or 300 millimetres where that level is known with confidence.
Uphill, the ground has its own history. The Northampton ironstone was quarried heavily from the late 19th century into the 1920s, and Camp Pit at Hunsbury was worked in the 1880s. Below the ironstone sits Whitby Mudstone, a clay the British Geological Survey lists among those that shrink and swell. If your house is near old workings or on clay, let the engineer dig a trial hole before the footings are drawn. Northamptonshire is also a radon-affected county, so ask building control whether the new floor needs protection.
Streets where the rules tighten
In Abington Park, Barrack Road, Billing Road, Kingsley, St Giles, Derngate, the Boot and Shoe Quarter and the old village cores of Duston and Kingsthorpe, a side addition or anything over one storey at the back needs permission, and so does cladding. A plain single-storey rear room can still be permitted development.
Six of those areas carry heritage Article 4 directions. Barrack Road's dates from 2000 and was made under the old article 4(2), which could only catch an enlargement facing a road, waterway or open space. Corner and end-of-terrace houses are the ones to check. Duston's 2009 appraisal names rear extensions among the piecemeal changes wearing down the village.
Where these facts come from
- West Northamptonshire Council: Northampton SPDs, incl. Residential Extensions and Alterations Design Guide (2011)
- West Northamptonshire Council: Northampton Local Plan Part 2
- GOV.UK: Permitted development rights for householders, technical guidance
- GOV.UK: Flood risk assessment standing advice
- Environment Agency: Dallington Brook and Brampton Branch flood warning area
- Environment Agency: River Nene and tributaries in Northampton
- Northamptonshire HER: Camp Hill desk-based assessment (ironstone quarrying)
- British Geological Survey: Northampton Sand Formation
- West Northamptonshire Council: Article 4 directions
- Duston Conservation Area Appraisal and Management Plan, 2009
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Questions people in Northampton ask
Our garden backs onto houses in the next street. Can we build a bedroom over the kitchen?
Measure the gap first. Northampton's 2011 design guide recommends at least 21 metres between facing back walls, and officers use it. A first floor that cuts that distance needs a strong design reason, such as high-level or obscure windows.
We live off Swansea Road in Dallington. Does flooding stop us extending?
No, but it changes the drawings. The street is in the Environment Agency's Dallington Brook warning area, so check the flood map. In Zone 2 or 3 any application needs a flood risk assessment and raised floor levels.
Can I put a two-storey side extension on my detached house in Northampton?
Only with planning permission, and the gap to your neighbour is the issue. Officers look hard at the space left beside the house, and losing the break between buildings has been a reason for refusal. Set the upper floor back from the front and down from the main roof so it reads as an addition.
Our end-terrace on Barrack Road faces a side street. Can we add a single-storey kitchen without applying?
Check before you assume. The area is a conservation area, and its Article 4 direction from 2000 was the kind that targets work facing a road or open space. Ask the council for the notice and confirm whether your side wall is caught.