What Cardiff counts as a parking space
People always ask whether the council will mind losing the car space. Cardiff's answer is a little unusual. Its July 2018 parking guidance, Managing Transportation Impacts, says that for the purpose of its standards garages are not counted as parking provision for homes at all. The standards are maximums, not minimums.
The same document wants a new garage to be 3.2 metres wide and 6 metres long inside. If yours barely takes a hatchback with the doors shut, it was never much of a parking space. The driveway in front is what matters. Cardiff's householder guide treats a standard space as 2.4 by 4.8 metres and says no car should hang over the pavement.
None of that is a free pass. The 2017 householder guidance says parking lost through a garage conversion will be assessed against the parking standards, and the 2018 guide warns that streets full of shared houses and flats may already be oversubscribed. A short drive on a road that's packed every evening invites questions.
Nor does it mean you need an application. The Welsh Government's line is that a garage conversion usually needs no planning permission if the work is internal and the building gets no bigger. The catch is a condition on the original consent, which gov.wales flags as a particular risk on new housing developments. Look your address up on the council's planning register and read the conditions before you book a builder.
Matching the conversion to the house
Integral garage. You won't find one on a Victorian terrace in Roath or Splott, which were built long before cars. Where a house has one, the council's 2017 guide asks that the new window and door match the house in proportion, materials and openings.
Single garage. Measure it before you plan anything. One at or above the council's 3.2 by 6 metre standard makes a decent room. Anything much smaller suits a study or utility better than a bedroom.
Read our full guide: Single Garage Conversion: What Is Involved and What to Budget For →
Bedroom. Welsh guidance asks for an escape window at least 450mm each way with 0.33 square metres of clear opening, its bottom edge no higher than 1100mm off the floor. A garage door opening gives you room for that. Check the flood map first if you live in the south of the city.
Home office. A sensible use for a short garage. It still counts as a habitable room for Building Regulations.
Utility or playroom. Keep the front half as a store and turn the back into a utility. A new utility room without an opening window needs an extract fan rated at 30 litres a second.
Double garage. Usually attached to a larger detached house. Converting one bay and keeping the other avoids most parking arguments.
Detached garage. Using it as a gym or office that belongs to the house is one thing. Making it a home someone lives in is a new dwelling. That needs planning permission and, under Welsh Building Regulations since 2016, a sprinkler system.
Gym or studio. The concrete slab copes with weights, but it will need a new damp membrane and insulation. Where it adjoins next door's garage, deal with sound through that wall before the kit arrives.
The two approvals. Planning is often not needed. Building Regulations approval nearly always is, from Cardiff Council's building control team or a registered approver. Keep the completion certificate for when you sell.
Cost. We don't put prices on this page. New foundations under the door opening and the floor build-up are what move quotes the most, so ask each firm what they've assumed for both.
Llandaff, Whitchurch and front doors facing the road
Swapping an up-and-over door for a window is the part of the job neighbours see. In most of Cardiff that's a matter of matching the house. Llandaff is different. Its Article 4 direction needs planning permission for altering, removing or renewing any door or window of a house where it fronts a highway, so a road-facing garage door is caught. New hard surfaces nearer the road than the house are covered too, so you can't quietly pave the lawn to replace the lost space.
The 2006 appraisal for Church Road in Whitchurch proposed the same kind of control over front doors, windows and hardstandings, and said keeping the planted front gardens and hedges may mean refusing a hardstanding altogether. In any of Cardiff's 27 conservation areas, ring the council before drawings are done.
Under the slab
Welsh Government guidance expects the old garage floor to need a new damp membrane and insulation, often finished with a screed of about 75mm, and it points to the BRE radon guide for floors. In Public Health England's 2016 report for Wales, 11 of the 250 Cardiff homes tested were at or above the Action Level, although testing leaned towards higher-risk spots. Check your postcode on the UK radon map.
The wall that fills the door opening usually needs its own foundation, because a garage normally sits on a thin slab. Southern Cardiff is built on soft estuarine clay, so let the engineer decide the depth. Where Natural Resources Wales's map puts a house in Flood Zone 2 or 3, think hard before putting a bedroom at garage level. Welsh flood policy treats every home as highly vulnerable and lists raised floors and high-level electrics as basic resilience.
Where these facts come from
- Welsh Government: planning permission for garage conversions
- Welsh Government: building regulations for garage conversions
- Welsh Government: garage conversion flooring
- Welsh Government: in-filling a garage door
- Welsh Government: building regulations for doors and windows
- Cardiff Council: Managing Transportation Impacts SPG (2018)
- Cardiff Council: Residential Extensions and Alterations SPG (2017)
- Cardiff Council: Llandaff Conservation Area Appraisal (2020)
- Cardiff Council: Church Road Conservation Area Appraisal (2006)
- Public Health England: Radon in homes in Wales, 2016 data report
- Welsh Government: TAN 15, development, flooding and coastal erosion (2025)
- Building (Amendment) (Wales) Regulations 2013: fire suppression
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Questions people in Cardiff ask
Will Cardiff Council object because I'm losing my garage parking?
Only where an application is needed, and even then the 2018 standards don't count garages as parking. Officers look at whether the drive still holds a car clear of the pavement and how busy the street is.
We're in Llandaff. Can we replace the garage door with a window?
Probably, but not without asking. The Article 4 direction there covers doors and windows facing the road, so a front-facing garage door needs planning permission. Match the house's materials and the council has less to argue with.
Can my mum live in our converted detached garage?
As part of the household, sharing your kitchen or garden and entrance, it can be treated as an annexe. Cardiff's guidance wants that kept modest. If it becomes a fully separate home it is a new dwelling, which needs planning permission and, in Wales, sprinklers.
Do I need to test for radon before converting?
It's sensible, as some Cardiff homes have tested above the Action Level. Tell building control what the UK radon map shows for your postcode, because a barrier is far easier to lay with the new floor than afterwards.