The 440mm step and the one-metre gap
Solihull planners judge extensions against their House Extension Guidelines, a supplementary planning document from February 2010. It is specific. Most councils talk about side additions looking subservient. Solihull gives you the measurements.
Going up over the side of a semi or detached house? The first floor should normally step back at least 440mm from the front wall. Where a semi has a cat-slide roof down the side, or a detached house has a shallow-pitched gable to the street, that rises to a metre. The new wing should be clearly narrower than the original house, and the guide expects a gap of at least one metre to the boundary in most cases, more on wide, leafy plots. The aim, in the council's words, is that any terracing effect between dwellings is avoided. A bedroom built over a three-metre garage right up to the fence is the classic case it resists.
Next door's windows matter as much as your boundary. The council draws a 45-degree line from the centre of the nearest main habitable room window in the neighbouring house. A first-floor addition that breaks it will normally be refused. Single-storey work is treated more flexibly, and the guide accepts that orientation and changes in level can count for as much as the line itself. If next door has a glazed conservatory, the line is taken from halfway along it.
On a corner plot, expect to keep a decent gap. The council values those side gardens, and drivers at the junction need to see round them.
Matching the build to the house
Each type below, set against Solihull's houses and rules, links to a longer guide.
Single-storey rear. Outside a conservation area you can usually go 3 metres out from the original back wall of a semi or terrace, or 4 on a detached house, without an application. The prior approval route allows 6 or 8 metres, but neighbours are consulted and you wait up to 42 days. Flat roofs are only welcome where nobody sees them from the road.
Two-storey. Almost always an application, and this is where the 440mm set-back and the 45-degree line bite. The roof should copy the pitch of the house. On a pair of inter-war semis in Shirley or Olton, matching the brick size, bond and mortar colour is what the planners will look for.
Kitchen. Glazing close to the boundary needs care here. The guide asks for obscured top lights on mostly glazed rooms near the fence, because a raised floor lets you see over it. Plan rooflights instead of a glass side wall.
Open plan. Knocking the old back wall through means a steel and padstones sized by an engineer. Under most of the borough the ground is clay-rich mudstone, so ask for the foundation design before the kitchen catalogue.
Wrap-around. Part of it runs beyond the side wall, so permitted development stops at half the house's width and one storey. In a conservation area there is no side element without permission at all.
Side return. Less usual in a borough of semis and detached houses than in a city of terraces. Where two houses share a one-metre passage, the council still wants the 440mm step back at the front.
Ground-floor bedroom. The number of Solihull residents in their seventies rose by 30% between the 2011 and 2021 censuses, so a downstairs bedroom and shower room is a sensible plan for many owners. Build in level thresholds from the start.
Home office. A detached garden room usually falls under permitted development, but the guide wants enough back garden left over. Attach it to the house and it gets heating and broadband off the existing supply.
Planning. First check whether the house is in one of the 20 conservation areas or the Green Belt, and whether an earlier permission took away permitted development rights. The council's Public Access register shows what has been approved on your road.
Cost. We don't give a Solihull price. Foundations on clay, steel, glazing and the finish you choose decide it, and a 1990s house in Dickens Heath is a different job from an inter-war semi in Lyndon. Three local quotes will tell you more.
Driveways, brooks and the Green Belt
One rule surprises people. A Solihull extension should normally leave six metres of usable driveway, or 4.8 metres where there is no garage. Building forward over the drive can fall foul of it. Front extensions are seldom approved anyway if they stand out or throw a pair of semis off balance.
Flooding is patchy. The council's 2017 flood risk study says the River Cole puts more homes at risk than the Blythe, mainly in Kingshurst, Chelmsley Wood and the Solihull wards, where its floodplain is narrow. Sewer flooding is reported most often in Solihull town, Dorridge and Hampton-in-Arden. If your house sits in Flood Zone 2 or 3, the application needs a flood risk assessment, and the extension guide asks for floors 300mm above the modelled 1-in-100-year river level.
Out in the Green Belt the cap is 40% of the original habitable floor space, measured externally. Original means as built, or as the house stood on 1 July 1948. Earlier additions count towards it, permitted development included, and so do permissions you never built.
White House Way and the older streets
On the 1960s White House Way estate an Article 4 direction means any extension to the side or front, of any size, needs permission, along with porches facing a road, new hardstanding and new fences or walls. Rear additions are not on that list, but a two-storey one at the back still needs permission because the estate is a conservation area.
In the town centre, Olton, Knowle and the other conservation areas, side extensions and two-storey rear extensions both need an application. So does cladding. Trees there over 75mm across at chest height are protected, so tell the council before a digger goes near one. Building control is in-house at the Council House on 0121 704 8008.
Where these facts come from
- Solihull MBC: House Extension Guidelines SPD (February 2010)
- GOV.UK: Permitted development rights for householders, technical guidance
- Solihull MBC: Strategic Flood Risk Assessment (JBA, 2017)
- Solihull MBC: White House Way conservation area appraisal
- Solihull MBC: conservation areas
- Solihull MBC: tree preservation orders
- Solihull MBC: Census 2021 first results
- Solihull MBC: building control application form (contact details)
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Questions people in Solihull ask
Can I build a bedroom over my garage in Solihull?
Sometimes. The council resists first-floor additions that run to the side boundary and create a terraced look. Expect to keep a one-metre gap and step the front back at least 440mm, which may mean the garage below is wider than the room above.
My neighbour's conservatory is next to where I want to extend. Does that stop me?
Not on its own. For the 45-degree test the council measures from the middle of the conservatory's depth, and single-storey work is judged more flexibly than first-floor work.
Will an extension over my drive be refused?
The guide expects six metres of usable driveway to remain, or 4.8 metres if you have no garage. Fall short and the planners may say no, so measure before you draw.
Do I need a flood risk assessment near the River Cole?
Only if the house is in Flood Zone 2 or 3. Check the Environment Agency map, and if you are in, the floor should sit 300mm above the modelled 1-in-100-year flood level.