Three metres along the fence, then a splay
Stockport planners judge house extensions against their Extensions and Alterations to Dwellings guidance, adopted in February 2011. For anything at the back, the number to remember is 3 metres. The guide says a single storey rear addition should not normally run further than that along or close to a shared boundary, particularly where it passes a neighbour's habitable room window.
It doesn't stop dead there. Beyond 3 metres a 45 degree splay is allowed, angling the far corner away from next door so the room can reach a little deeper. That chamfered corner is usually cheaper than arguing.
Two storeys on the boundary get a firmer answer. The guide says to avoid them, "even more so on the south facing side", where the shadow falls straight onto the house next door. If you want more bedroom space at the back, pull the upper floor in from the party wall and keep the single storey part against it.
All of this only bites if you make a planning application, and officers apply it case by case. Within permitted development it never comes into it. Go past the national limits, though, and this is where the council starts.
Semis and the one metre gap
Stockport is a borough of semis, from Edwardian Heaton Moor to Bramhall estates of the 1960s such as Parkside. The obvious way to grow one is sideways over the drive, and that is where the council is most careful.
A two storey side addition should sit at least one metre back from the front wall, or one metre in from the side boundary, with its ridge lower than the main roof. The aim is a visible gap. In the guide's words, houses "should not be physically or visually linked, particularly at first floor level", because a street of semis joined up above the garages starts to look like a terrace.
The front is harder still. On a street with a strong building line, front additions are unlikely to be acceptable, though a porch that copies the house's roof pitch and materials normally is. Adding a whole storey? Planners expect that only on detached houses.
Matching the job to the house
Roughly in the order people here ask about them.
Single storey at the back. Permitted development allows 3 metres on a semi or terrace and 4 on a detached house, or 6 and 8 through prior approval, where neighbours get a say. Inside any of the 37 conservation areas the basic right stays but the prior approval route goes.
Kitchen. The usual brief on a three bedroom semi. If you need to apply, the 3 metre line along the shared fence will shape the room before the budget does, so ask your designer to try the splayed corner early.
Two storey. Permitted development caps it at 3 metres deep and 7 metres from the back boundary, and rules it out in conservation areas. It usually works best on the side of a semi away from the party wall.
Side return. Made for the red-brick Victorian terraces around Reddish, where a back wing leaves a narrow yard beside it. Under permitted development it stays single storey, no higher than 4 metres and no wider than half the house.
Wrap-around. Counts as a side extension as well as a rear one, so in a conservation area it needs permission. Planners look hard at how the side leg of a corner semi meets the road.
Open plan. Opening the back of a Heaton Moor semi or a Reddish terrace into a new room means a steel, and Stockport building control names steel beams as an inspection stage. Get the engineer's calculations before the builder quotes.
Downstairs bedroom. A single storey side addition over the drive of a semi can take a bedroom and level access shower room. Draw wide doors and turning space in from day one.
Home office. Attached usually wins on a suburban Stockport plot, with heating and broadband from the house. Under permitted development, extensions and outbuildings share one half-of-the-garden limit anyway.
Planning. Before paying for drawings, find out whether your street is in a conservation area and whether your plot sits in a flood zone. Either answer changes the paperwork.
Cost. No figure from us. A brick semi in Cheadle Hulme and a stone cottage in Marple need different foundations and different materials, and only site visits will price that.
Rivers, boulder clay and the Green Belt
Stockport grew where the Tame and Goyt meet to form the Mersey, so flood risk follows the valleys. The Environment Agency's warning area for the Goyt and Mersey runs from New Bridge Lane to junction 2 of the M60, taking in Great Portwood Street, Heaton Lane and Chestergate. Upstream, its Marple Bridge warning covers homes on Brabyns Brow and Low Lea Road. To the west, the Middle Mersey flood alert names Cheadle, Cheadle Hulme and Gatley, along with the Micker Brook.
If your plot is in Flood Zone 2 or 3, a planning application needs a flood risk assessment with it. For a householder job, the Environment Agency's standing advice for minor extensions sets out what to cover, such as floor levels.
Underfoot, much of the borough sits on glacial deposits the British Geological Survey calls the Stockport Glacigenic Formation, a mixed bag of gravelly clay with boulders, sand and laminated clay. Let the inspector see the trench before any concrete goes in.
On the rural edges, Green Belt policy takes over. Stockport's saved policy says extensions adding more than about a third to the volume of the original house are unlikely to be acceptable, and earlier additions count towards that.
Where these facts come from
- Stockport Council planning committee report quoting the Extensions and Alterations to Dwellings SPD (2011)
- Stockport Council planning committee report quoting the SPD on side and rear extensions
- Stockport Council planning committee report on Green Belt policy GBA1.5
- GOV.UK: Permitted development rights for householders, technical guidance
- Stockport Council: Article 4 directions
- Environment Agency: Rivers Goyt and Mersey at Stockport flood warning area
- Environment Agency: River Goyt at Marple Bridge flood warning area
- Environment Agency: Middle River Mersey catchment flood alert area
- GOV.UK: flood risk assessments for planning applications
- Environment Agency: flood risk standing advice
- BGS Lexicon: Stockport Glacigenic Formation
- Stockport Council: booking a building regulations inspection
How FirQuote works in Stockport: We connect you with local specialists who visit your property before giving you a price. You get up to 3 written quotes — no call centres, no estimates from photos, no obligation to accept any quote.
Questions people in Stockport ask
Will Stockport Council approve a 4 metre extension along my party wall if I apply for planning permission?
Possibly, but not as a straight 4 metre wall. The council's guide normally expects 3 metres along a shared boundary near a neighbour's window, with a 45 degree splay allowing a little more beyond. The other route is prior approval, which can allow up to 6 metres on a semi or terrace if neighbours' objections don't sink it.
Does the Article 4 direction in Heaton Moor stop me building at the back?
The council's Article 4 page covers things like windows, roofs, porches and boundary walls, not rear extensions. Being in a conservation area matters more. You keep the basic single storey rear right, but not side additions, two storeys at the back or new cladding.
I'm in Cheadle near the Micker Brook. Do I need a flood risk assessment for a kitchen extension?
Only if you're making a planning application and the plot is in Flood Zone 2 or 3. Check the government's flood map for planning first. Within permitted development there is no application to send.
Can I build a two storey side extension right up to the boundary of my semi?
Not under permitted development, which only allows single storey side additions. With planning permission, Stockport's guide wants it one metre back from the front wall or one metre off the boundary, with a lower ridge, so that it doesn't join your house to next door.