An island with nowhere to go but up
Most of Portsmouth sits on Portsea Island, and the council's own description is hard to improve on. Flat, low lying, laid out in rows of artisan terraces on a grid, built for dockyard workers and seafarers' families. It is the most densely populated authority in the South East. Gardens are small and plots are tight, so the roof is usually the only place left to find another room.
Off the island, the picture changes. The mainland suburbs between Paulsgrove and Farlington are mostly larger 1930s semis, and those roofs suit a different kind of conversion. Wartime bombing destroyed over 6,000 buildings in the city, and estates such as Paulsgrove, Landport, Somerstown and Buckland were rebuilt between the late 1940s and the 1970s. Roofs from that period vary a lot, and some are better left to a surveyor before anyone talks about dormers.
Picking a conversion for a Portsmouth roof
Here is how each type tends to sit on the city's housing. Every one links to a longer guide.
Rear dormer. The usual answer for an island terrace in Fratton or Southsea. A full-width box on the back slope turns a cramped roof void into a proper room, and outside a conservation area it is often permitted development.
L-shaped dormer. Where a terrace has a back addition, a second dormer over it gives you two rooms instead of one. On a narrow plot that second section is usually where the shower room goes.
Hip to gable. Mainly a mainland job. Where a 1930s semi in the northern suburbs has a hipped end, squaring it off to a gable is what makes the loft wide enough for a staircase.
Read our full guide: Hip-to-Gable Loft Conversions: What It Involves and Which Houses It Suits →
Rooflights only. Often the realistic choice in Southsea's conservation areas, where a dormer needs consent on any slope. Some of Owen's houses have low-pitched slate roofs, though, so check the headroom first. Rooflights won't help much if you can't stand up under the ridge.
Mansard. Nearly always a planning application, and the council's Old Portsmouth guidance discourages large roof extensions on fronts that face the street. Where one is allowed, expect to match the existing building's materials.
Extra bedroom. What most island families are after. If you plan to let that room to a sharer, read the FAQ below first, because Portsmouth controls that change more tightly than most cities.
En-suite. Worth planning in from day one. In a narrow terrace the soil stack position decides almost everything, and moving it later is messy.
Home office. A small rear dormer makes a quiet office above a busy street. Get a data cable run up while the walls are open.
Read our full guide: Loft Home-Office Conversion: What Works Well Up There and What to Specify →
Planning. Outside conservation areas, many rear dormers here go ahead under permitted development. Flats get no such rights at all. Check before you pay for drawings.
Cost. No figure here. A terrace with a sound roof and a stucco villa with a shallow slate pitch are different jobs, and a web page price would mislead you. Three site visits will.
Southsea's slate roofs and the rules that come with them
Portsmouth has 25 conservation areas, and a good number are in Southsea: Owen's Southsea, Stanley Street, The Terraces, Castle Road, Campbell Road, East Southsea and Craneswater and Eastern Parade among them. Owen's Southsea was designated in 1969 and covers the terraces and villas Thomas Ellis Owen and others built from the 1830s. His Portland Terrace, from the late 1840s, is stuccoed brick under low-pitched slate roofs with deep boxed eaves. Lovely to look at, not much room inside.
In any conservation area, a dormer, a hip to gable or a mansard needs planning permission, whether it faces the street or the back garden. Some Southsea houses also carry an Article 4(2) direction, set street by street and house by house. The ones on Stanley Street, St Edward's Road and Yarborough Road, and those across Owen's Southsea, remove rights to change front windows and doors, chimney stacks, front boundary walls and the roof covering on the slope facing the road. So keep the chimney, and don't swap the front slates for concrete tiles while the scaffold is up.
Old Portsmouth has its own council guidelines. Large dormers are to be kept mostly to the rear roofscape, interlocking concrete tiles are discouraged, and the council points to Spice Island as a place where roof extensions have been done well.
Who checks the work
Planning applications go to Portsmouth City Council at the Civic Offices, and you can search the council's Public Access register by street. Seeing what neighbours were allowed is the quickest guide to what will get through.
Building control is not run by the city alone. It is the Building Control Partnership, shared with Fareham, Gosport and Havant and based in Fareham. Your structural engineer should look at the ground as well as the roof. The British Geological Survey records brickearth, flint gravels and clays across the island, varying over short distances, so new steels resting on old walls deserve a proper check. Keep the completion certificate with your deeds.
Where these facts come from
- Portsmouth City Council: conservation areas
- Portsmouth City Council: Owen's Southsea conservation area
- Portsmouth City Council: Article 4(2) direction, St Edward's Road and Yarborough Road
- Portsmouth City Council: city-wide HMO Article 4 direction
- Portsmouth City Council: Old Portsmouth conservation area guidelines
- Portsmouth City Council: building control
- Portsmouth City Council: Solent special protection areas
- Historic England: Furness Villa, Southsea
- British Geological Survey: Portsea and Hayling resurvey
- ONS: Census 2021 population change, Portsmouth
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Questions people in Portsmouth ask
Can I add a loft room and let it to sharers?
Not without asking. Since 1 November 2011 an Article 4 direction across the whole city has removed the right to turn a family house into a small HMO, so the change needs planning permission and an HMO licence as well. The loft itself may be permitted development, but the change of use is not.
I own a converted flat in Southsea. Can I go into the roof?
Not under permitted development. Flats don't have those rights, so any dormer needs a full planning application, and in a conservation area the bar is higher. Check your lease too, because the roof space may not be yours to build into.
My house is covered by an Article 4 direction on St Edward's Road. Does that stop a loft conversion?
Not by itself. The direction protects the street face, such as front windows, chimneys and the front roof covering. The street is in a conservation area, so a rear dormer needs planning permission anyway. Plan to keep the chimney and the front slope as they are.
Could I turn the top floor into a separate flat?
That is a new home, not a loft conversion, so it needs full planning permission. Every net new dwelling within 5.6 km of the Solent's protected sites pays a Bird Aware contribution, and the council also applies its nitrate mitigation strategy to new housing. Talk to the planners before anyone draws plans.