Along the foot of Portsdown Hill
On Portsea Island most people never had a garage. The Portsmouth Plan, adopted in 2012, describes the island as rows and rows of artisan terraces on a grid, and a terrace that opens straight onto the pavement has nowhere to put one. Garages arrive once you cross onto the mainland.
The plan sketches that northern strip too. Paulsgrove, Wymering, Cosham, Drayton and Farlington line the slopes of Portsdown Hill, running from post-war development in the west to larger detached homes in the east, with plenty of 1930s semis in between. It also notes that big detached houses are relatively rare in the city. So most conversions here mean one single garage beside a semi, and a double is the exception.
Three metres by six, measured inside
Portsmouth's parking standards SPD, adopted in July 2014, sets the size a garage must be before the council will count it as a car space. A single needs 3 metres by 6 inside, with a door at least 2.3 metres wide. A double needs 5.5 metres by 6, and the council wants a 7 metre length where bikes are kept in there too.
Older garages can be narrower. Then it may never have counted as parking, so measure it first. The space in front matters more: the SPD wants 3 metres by 5 for a car parked square to the house, and asks for permeable surfaces wherever they can be used.
The same document is blunt about newer housing. It says the council may remove permitted development rights to stop garages, car ports and other parking spaces in new developments being lost later. On a house built in the last few decades, look at the planning permission for the estate before you commission plans, or ask the planners to check it for you.
If an application is needed, the SPD measures parking against bedrooms. For a house being extended or converted, it counts the bedrooms you add. A third bedroom becoming a fourth adds half a space, which rounds up to one, and that is on top of the space the garage itself used to provide.
Which conversion suits which house
Single. The everyday job in Cosham and Drayton. The tricky bit is the old door opening, where the footing under the threshold often turns out to be shallow or missing once it is dug out.
Read our full guide: Single Garage Conversion: What Is Involved and What to Budget For →
Integral. More likely on later estates than on the 1930s semis. These are the houses where the 2014 SPD's warning about removed rights bites, so check that first.
Office. A converted garage is one of the few ways to get a quiet room for work without touching the roof. Inspectors treat it as habitable, so it is insulated to the same standard as a bedroom.
Bedroom. If the room can only be reached through another room, LABC asks for an escape window with a clear opening of 450 by 733mm, its sill no more than 1.1 metres up. In a house let to sharers, a garage bedroom that pushes the count past six needs planning permission.
Utility or playroom. Putting the washing machine at the back and toys at the front can work well in a single garage. Adding a WC means connecting to the drains, and the partnership's guide suggests asking the water company where the sewer runs before you design around it.
Gym or studio. Pairs of semis often have garages built side by side. LABC says a party wall thinner than 200mm of dense block usually needs extra sound work, and weights dropping at 6am will test it.
Double. Likeliest on the larger detached houses at the eastern end of the hill. Splitting one into a room and a store keeps the bikes dry, and the SPD wants a detached store to be secure if it counts as cycle parking.
Detached. A study or gym used with the house is one thing. A self-contained home for someone else is another, and the Planning Portal says that can need permission whatever the building work. The Building Control Partnership's guide goes further and treats a detached conversion as a change of use, so speak to the planners first.
Planning and building control. Planning permission usually isn't needed for work inside the shell that leaves the building the same size. Inspection is another question. The partnership's guide says every conversion needs approval, and it issues a completion certificate after the final inspection.
Cost. No Portsmouth prices on this page. The ground under the door, the floor level and whether the drive needs a new dropped kerb move the figure more than the room's finish does.
Front gardens, low floors and who signs it off
In Southsea's conservation areas the front is what the council protects. A few streets carry Article 4 directions that go as far as the front garden. In Owen's Southsea, the direction for Richmond Terrace, Netley Place and part of Netley Road removes the right to lay a hard standing there, so a new parking space out front needs permission.
A new kerb crossing goes through the council's highways contractor. You can use your own builder for the work, but the highways contractor has to approve anything done to the public highway.
Ground level is the other check. The Portsmouth Plan puts around a third of the city's land in the tidal floodplain, and garage slabs usually sit below the house floor. Where your address is in Flood Zone 2 or 3, the Environment Agency's standing advice recommends floors at least 600mm above the estimated flood level, or flood-resistant materials where that can't be done. A bedroom is where that matters most. Look your address up on the UKradon map as well, because conversions in the higher bands need basic or full radon protection.
Inspections for the city are carried out by the Building Control Partnership, shared with Fareham, Gosport and Havant. Let them know within five days of finishing, and keep the certificate with the deeds for when you sell.
Where these facts come from
- Portsmouth City Council: Parking standards and transport assessments SPD (2014)
- Portsmouth City Council: The Portsmouth Plan (adopted 2012)
- Portsmouth City Council: Owen's Southsea conservation area and Article 4 directions
- Portsmouth City Council: dropped kerbs and entrance markings
- Building Control Partnership: how to plan a garage conversion
- Building Control Partnership: frequently asked questions
- Planning Portal: garage conversion planning permission
- LABC: garage conversion tips from building control
- LABC: do I need to consider radon?
- GOV.UK: flood risk assessment standing advice
How FirQuote works in Portsmouth: 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 Portsmouth ask
Our garage in Drayton is only about 2.5 metres wide. Does the council count it as parking?
Under the 2014 parking standards SPD, a single garage needs to be 3 metres by 6 inside to count as a car space. Show the internal size on your plans if an application is needed.
Could converting our garage leave us short of parking under the council's standards?
Only if the work needs planning permission. Then the SPD looks at the bedrooms you add, so turning a three-bed into a four-bed raises the expected parking by half a space, rounded up to one.
We live on Netley Road. Can we pave the front for the car once the garage goes?
Some houses there are covered by an Article 4 direction removing the right to lay a front-garden hard standing, so check your number with the council before booking anyone.
The previous owner converted the garage without approval. What now?
The Building Control Partnership accepts regularisation applications for work done after November 1985. You may have to open up parts of the floor or walls so the inspector can see them.