Four metres by right, three and a half on paper
Two sets of numbers matter in Wrexham, and they don't agree. Welsh permitted development lets you build a single storey addition up to 4 metres beyond the original back wall, and up to 4 metres high, on any kind of house. Terraces and semis get the same as detached homes. Keep the eaves to 3 metres if you're within 2 metres of a boundary, and don't cover more than half the garden around the house as first built.
Once you need an application, the council turns to its Local Planning Guidance Note 20, House Extensions, last updated in March 2010. It is stricter. Anything built within a metre of a boundary will normally be held to 3.5 metres long, with an extra metre allowed for every extra metre you step away. A 4 metre kitchen that is fine as permitted development can look too deep to an officer once it needs consent for another reason, perhaps a taller roof.
Officers also draw the 45 degree line. Take it down from the near top corner of the new wall on the elevation, and back from its end on the plan. If the middle of next door's main window sits on your side of both lines, expect questions about lost light. Passing doesn't guarantee approval, the council says, and failing doesn't guarantee refusal.
Gardens, gaps and Victorian streets
The guidance wants at least 50 square metres of usable private garden left behind, or 30 for a small house for one or two people. Facing habitable windows should be 22 metres apart, and a window looking at a wall taller than itself needs 13 metres.
For side additions the council recommends leaving a metre to the boundary and stepping the front back by about a metre, so a row of semis doesn't fuse into a terrace. A pitched roof will normally be expected. Corner plots are limited to half the original frontage.
The county borough has 12 Article 4 directions. In the city they cover Salisbury Park, Fairy Road and Gerald Street, and further out villages such as Holt and Rossett. The council says these bite on work fronting a road, footway, waterway or open space. A rear kitchen out of public view isn't caught by the direction, though conservation area status still applies. In any Welsh conservation area nothing over one storey is permitted development, a side addition is held to 3 metres and set a metre behind the front wall, and new render or cladding needs consent. The Grosvenor Road appraisal calls flat roofs unacceptable.
Which job suits which Wrexham house
Single storey rear. Usually the simplest route, because the Welsh 4 metre allowance applies to every house type. Check the planning history before you start, since a condition on an estate consent can remove the right.
Kitchen. Red brick houses need bricks to match the old walls. Size the glazing to the room, not the catalogue.
Side return. Worth a look on an older terrace with a back addition and a strip of yard beside it. Where infill needs consent, anything within a metre of the boundary falls under the 3.5 metre length guide.
Open plan. Taking out the old back wall means a steel and an engineer's calculations. On a semi or terrace serve Party Wall Act notice first, because the Act applies in Wales.
Two storey. Always an application in a conservation area. Elsewhere the council wants two storey rear work kept 2 metres off a party wall boundary and a metre off others. Narrow semis rarely have the width.
Wrap-around. Best on a detached house or a wide semi on the private estates. Expect to apply, with the side leg judged on the metre gap and the set-back.
Ground floor bedroom. Keep it plainly part of the house. A self-contained annexe is treated differently and can be caught by the River Dee phosphate rules, which ordinary extensions escape.
Home office. Attached to the house, it counts against the same 4 metres and the half-garden limit.
Planning. English figures don't apply here. If you're unsure, the Welsh Government suggests a Lawful Development Certificate.
Cost. We don't publish a Wrexham figure. Foundations on wet till or near old mine workings can change a quote more than the kitchen does, so get prices after a site visit.
Soft ground, old shafts and the drains
Footings deserve the most thought here. The British Geological Survey describes most of the city as glacial sand and gravel, water-bearing in places, with till that softens quickly when wet. Around King's Mills and Cefn Park glacial silts can run in an open trench, and along the Clywedog there is soft alluvium with peat. Ask the groundworker which one they expect before the concrete is booked.
Old coal workings matter too, with some 1,350 shafts and adits on record locally. A householder application doesn't need a coal mining risk assessment, but foundations that might disturb old workings need a Mining Remediation Authority permit, and the building inspector may want evidence that the ground will stay put.
Building over or within 3 metres of a public sewer needs the sewerage company's consent, so ask which company serves your street. On flooding, the council's flood plan picked out Acton, Caia Park, Offa and Rhosddu for surface water, with the culverted Gwenfro adding risk in Caia Park and Offa. If the Natural Resources Wales flood map puts your house in Zone 2 or 3, an application needs a flood consequences assessment sized to the job.
Where these facts come from
- Welsh Government: planning permission for extensions
- Welsh Government: permitted development for householders, technical guidance
- Wrexham Council: Local Planning Guidance Note 20, House Extensions
- Wrexham Council: conservation area management and Article 4 directions
- Wrexham Council: Grosvenor Road conservation area assessment
- Wrexham Council: river phosphate targets
- British Geological Survey: engineering geology of the Wrexham area
- GOV.UK: home extensions in former coal mining areas
- Dลตr Cymru Welsh Water: building over or near sewers (example of the consent rules)
- Natural Resources Wales: Flood Map for Planning
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Questions people in Wrexham ask
We're in Salisbury Park. Can we still build at the back without applying?
Possibly a single storey one. The Article 4 direction there covers work fronting a road, footway or open space, so a rear kitchen out of view isn't caught by it. Conservation area limits still apply, so nothing over one storey.
Our house is in Caia Park. Will flooding stop us extending?
Not usually by itself. Check the Natural Resources Wales flood map first. If you're in Zone 2 or 3 an application needs a flood consequences assessment. Within permitted development there's no application at all.
Next door got 4 metres without planning. Why is the council talking about 3.5?
Their extension was probably permitted development, which allows 4 metres on any house in Wales. The 3.5 metre figure is the council's guide for applications covering work within a metre of a boundary.
We're outside the city near Rossett. Is there a size limit?
Outside settlement limits the council's guidance says an extension shouldn't normally be more than a third of the original floor area. Rossett is also a conservation area with an Article 4 direction, so talk to the planners early.