Four metres on a terrace, three on a semi
Bolton's planners are unusually relaxed about the back of a terraced house. Their House Extensions guidance, approved in August 2012 and still the council's current document, says a single or two storey rear addition on a terrace of up to 4 metres will normally be acceptable, measured from the original back wall. Semis are held to 3 metres for a single storey and detached houses to 4.
Why the generosity? The guidance admits that applying it will cause more loss of light next door, but says better living conditions in cramped terraced homes deserve real weight. It even allows a single storey to go further than 4 metres if what's left of the yard would be unusable anyway, or if you're building up against a neighbour's existing back addition.
There's a price for that. The same section says full width additions on terraces are unlikely to be allowed, because a row of them creates what it calls a tunnel effect between houses. Follow the pattern already on your row. And talk to the people next door first, since the council strongly encourages joint, handed schemes built as mirror images.
None of this applies within permitted development. Go beyond 3 metres on a terrace without prior approval and you'll be applying, so read it first.
The tests an officer will run
Expect the 45 degree check, a line from the centre of your neighbour's nearest main room window that your addition shouldn't cross. Bolton calls it a rule of thumb. It adds that a mostly glazed conservatory can sometimes go longer.
Going up a storey at the back of a semi or detached house? The guide wants it at least 2 metres off any shared boundary. Going up at the side, keep 1 metre to the boundary. Can't manage that? Then step the first floor back from the front and drop the roof, so the house doesn't visually join up with next door. The guide calls flat roofed two storey side additions visually unacceptable.
Then there's space. On a semi or detached plot the council treats about 50 square metres of private garden as a reasonable minimum after building, though it accepts that can't work in terraced streets. A garage or car port should keep a parking space about 6 metres long in front of it. Terraces must keep somewhere for the bins.
Which addition suits a Bolton house
Single storey at the back. Permitted development lets a terrace or semi go 3 metres without an application, or up to 6 with prior approval. If you make a full application instead, a terrace has the council's 4 metre guideline to work with.
Kitchen. On a yard-backed terrace the kitchen is most often the room being extended. Because full width is unlikely to be approved, plan a narrower room with good light from above rather than chasing every last centimetre.
Side return. Suits an older terrace whose back wing has a passage alongside it. Remember the tunnel effect warning, and check whether neighbours have already filled theirs before drawing yours.
Two storey. Almost always an application, since permitted development caps it at 3 metres deep and 7 metres from the back boundary. Bolton's 21 metre spacing between facing main room windows is offered as layout guidance, not a fixed minimum.
Open plan. Taking out the back wall of a brick terrace means a steel and an engineer's calculations, both checked by the council's own building control team. Sort that before asking for prices.
Wrap-around. Better suited to the semis of Westhoughton or Astley Bridge than to a terrace. The side leg counts as a side extension, so it needs permission in any of the 26 conservation areas.
Downstairs bedroom. Bolton's guide says the council may depart from its normal rules for someone with a disability, given evidence such as a professional needs assessment. It suggests speaking to the council's occupational therapist before applying.
Home office. On a semi, an attached study eats into the same garden as a cabin would, so keep the 50 square metre guide in mind either way.
Planning. In a conservation area there's no side extension or two storey rear addition under permitted development, and every application there needs a heritage statement. Barrow Bridge also has an Article 4 direction, so ask before assuming anything there.
Cost. We don't publish Bolton prices. The guide does make one money point, that a flat roof can be cheaper to build but costly to repair or replace later.
Rivers, culverts and the moors
Most of Bolton sits well clear of river flooding, but not all. The council's strategic flood risk assessment puts the highest river risk in Kearsley, below where the Croal meets the Irwell. It also shows the flood zones reaching furthest along the lower Tonge towards the Croal, and a small patch of Flood Zone 3a around Church Wharf in the town centre. Build in Flood Zone 2 or 3 and any planning application needs a flood risk assessment, which for a small household addition follows the Environment Agency's standing advice.
Surface water is the wider problem. The same report lists Horwich, the town centre, the inner Bolton renewal areas, Little Lever and Kearsley as susceptible, and notes that many incidents happen in culverted brooks. Know where any culvert runs before the footings are set out.
Ground is mostly glacial till over Coal Measures. Bolton doesn't ask for a coal mining report with a householder application, but national guidance still says that in a development high risk area you must check the mining risk, avoid building over a mine entry, and get a permit if the digging could disturb old workings.
For homes in the Green Belt, policy CG7AP from the 2014 Allocations Plan allows extensions that don't add disproportionately to the original building. Bolton sets no percentage, so expect the officer to judge it on the drawings.
Where these facts come from
- Bolton Council: House Extensions SPD (2012)
- GOV.UK: Permitted development rights for householders, technical guidance
- Bolton Council: Allocations Plan written statement (2014)
- Bolton Council: Strategic Flood Risk Assessment
- GOV.UK: flood risk assessments for planning applications
- GOV.UK: home extensions in former coal mining areas
- Bolton Council: local validation checklist
- Bolton Council: Article 4 direction in conservation areas
- Bolton Council: supplementary planning documents
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Questions people in Bolton ask
I live in a terrace in Halliwell. Can I go 4 metres out the back?
Without an application, no. Permitted development stops at 3 metres for a terrace unless you use prior approval, which allows up to 6 after the council has notified neighbours. With a full application, Bolton's guide says 4 metres is normally acceptable on a terrace, though probably not across the whole width of the house.
My neighbour and I both want to extend our semis. Should we apply together?
Bolton actively encourages it. Its guide says joint, handed proposals reduce overshadowing and maintenance problems and keep the street looking consistent.
Our house in Kearsley is near the Irwell. What extra do we need?
Look up the plot on the government's flood map for planning. If it falls in Flood Zone 2 or 3, a planning application has to include a flood risk assessment. For a minor household extension that means following the Environment Agency's standing advice on floor levels and flood resistant materials.
Our house is in the Green Belt. How big can we go?
There's no fixed figure in Bolton. Policy CG7AP only says additions mustn't be disproportionate to the original building, so earlier extensions count against you. Keep the new part clearly smaller than the house.