Loft Conversions in South East London: Which Loft Suits the Terraces of Lewisham, Southwark, Greenwich, Bromley and Bexley, the Conservation Areas, and Prices
By Anderson & the LCCL Construction Team | Finchley N3
South east London — Lewisham, Southwark, Greenwich, Bromley and Bexley — holds more Victorian terraces than any other part of the capital, street after street of them from Peckham and Nunhead through Brockley and Catford to Plumstead, nearly all with a two-storey rear outrigger and a slate roof. Behind them sit the Edwardian semis of Blackheath, Lee and Eltham, and beyond those the 1930s hipped semis that fill Bromley, Bexleyheath and Sidcup. Each house type takes a different loft, and each borough has its own planning habits and conservation areas. This guide takes them in turn.
As LABC Building Excellence Award Winners 2024 for Best Residential Extension in London — and London Regional Winner 2026 for Best Conversion or Alteration to an Existing Home — we design and build lofts across south east London from our Finchley base, and the terrace loft we built in Lewisham SE3 — a double bedroom with an en-suite and double doors with a balustrade at the rear, built under a temporary roof — is the project described below.
Not sure whether your project needs planning permission? Enter your postcode and tick what you want to build — about two minutes, free, and the from-price for each part that qualifies appears on screen and in your inbox.
The house decides the loft
On the Victorian terrace with an outrigger — most of Lewisham and Southwark and the older streets of Greenwich — a rear dormer across the main roof gives one room of 20 to 30 square metres, and an L-shaped dormer that adds a second dormer over the outrigger gives two rooms or a room and a proper bathroom, 30 to 40 square metres in all. The three-storey Victorian villas of Brockley and Telegraph Hill have tall roofs that often take a rooflight loft with no change to the roof shape. The Edwardian and 1930s semis of Blackheath, Eltham, Bromley and Bexley have hipped roofs, so the standard answer is a hip-to-gable with a rear dormer behind it, 25 to 35 square metres. And where the ridge is low — some of the smaller terraces of Deptford and Woolwich — a mansard is the only loft that gives standing headroom, and it always needs a planning application.
Is a loft conversion permitted development in south east London?
Outside the conservation areas, usually. A loft on a house (not a flat) is permitted development where the new roof space stays within 40 cubic metres on a terraced house — an end-of-terrace counts as a terrace — or 50 cubic metres on a semi or detached house, nothing rises above the existing ridge, no dormer faces the road, the materials match the house, side windows are obscure-glazed and the dormer sits at least 200 mm back from the eaves. A rear dormer on a terrace typically adds 30 to 40 cubic metres; a hip-to-gable with a dormer on a semi, 45 to 50; a full-length L-shape can tip over 40 and is sized to what is left. The allowance is a volume, not a floor area — 40 cubic metres on a terrace (an end-of-terrace counts as a terrace), 50 on a semi or detached house, measured on the outside of the new roof; here is how the 40 and 50 m³ rule works for each loft type.
The conservation areas are where south east London differs from the north and west: they are large and they cover whole neighbourhoods rather than single squares. Brockley is one of the biggest in London; Telegraph Hill, Blackheath, Greenwich Park and West Greenwich, Camberwell Grove, Peckham Rye and the Dulwich estate — where the Dulwich Estate's own Scheme of Management applies on top of Southwark's planning — all remove the dormer and roof-enlargement rights, so a loft that changes the roof shape there is a householder planning application (£548, eight weeks); a rooflight loft usually stays permitted development. The boroughs' records differ too: in the year to June 2026 Bexley was among the fastest London boroughs to decide householder applications and Bromley handled the most of them, 1,609, with Lewisham and Southwark in the middle of the table (see our borough planning-speed ranking). Our Planning check reads the conservation-area and Article 4 data for your postcode first; the council has the final say on any application.
Not sure whether your project needs planning permission? Enter your postcode and tick what you want to build — about two minutes, free, and the from-price for each part that qualifies appears on screen and in your inbox.
Building control across the five boroughs
Building regulations apply to every loft whatever the planning route, and the inspection is the same whichever council you are in: the new floor structure and the steel beams before they are covered, the staircase and its headroom, the fire-protected escape route from the loft to the front door with FD30 fire doors on the rooms that open onto it, the insulation and ventilation of the new roof, and the finished loft before the completion certificate is issued. On a terrace both party walls carry steel, so notices under the Party Wall Act go to both neighbours; south east London's clay and its street trees are a foundations question for extensions rather than lofts, but they are why a loft and an extension together are surveyed as one job. Our structural engineer produces the calculations and the drawings go to building control before the scaffold goes up.
What a loft conversion costs in south east London
Velux / rooflight loft: from £32,400 inc. VAT (£27,000 + VAT), 15–25 m², four to six weeks on site.
Rear dormer: from £56,400 inc. VAT (£47,000 + VAT), 20–30 m², six to eight weeks on site.
L-shaped dormer: from £58,800 inc. VAT (£49,000 + VAT), 30–40 m², eight to ten weeks on site.
Hip-to-gable with rear dormer: from £60,000 inc. VAT (£50,000 + VAT), 25–35 m², eight to ten weeks on site.
Mansard: from £76,800 inc. VAT (£64,000 + VAT), 30–45 m², ten to fourteen weeks on site, planning application always required.
Every figure is design and build at economy specification, shell-and-plaster finish, and includes the survey, the drawings, the structural calculations, building control and a 12-month workmanship guarantee, with a 10-year LABC structural warranty on every project. The final price is fixed in writing after the survey and is postcode dependent. A loft built together with a rear or side-return extension starts from £98,400 inc. VAT (£82,000 + VAT) under one contract — the combination most south east London families end up with.
Our project in Lewisham SE3
On a terraced house in Lewisham SE3 we designed and built a loft conversion with a large double bedroom and an en-suite, finished with double doors and a balustrade at the rear so the room opens to the garden side. The rear roof came off under a temporary scaffold roof — the tin hat — so the house stayed dry while the new floor and steels went in, and the front roof was supported throughout. It is the loft a south east London terrace takes most often, and the same sequence we follow from Peckham to Plumstead: scaffold, tin hat, steels, floor, dormer, stair, finish.
Anderson's advice
If the house is in Brockley, Blackheath, Telegraph Hill or anywhere else with a conservation area, ask about the rooflight option before you ask about the dormer. A Velux loft stays permitted development inside a conservation area, costs from £32,400 and is on site for four to six weeks; a dormer there is an application, a design the officer judges, and usually a longer wait. On the tall Victorian villas of these neighbourhoods the roof is often high enough that rooflights give a real bedroom — our team measures the ridge at the survey and tells you which route the house allows before anyone draws anything.
What our clients say
“used LCCL construction for my loft conversion. Very happy with the works, arranged everything from planning to finish. completed on time with no hassle.”
— Brian Edwards, Google Reviews
Frequently asked questions
Do I need planning permission for a loft conversion in south east London?
Outside the conservation areas, usually not: a rear dormer, L-shaped dormer or hip-to-gable within the 40 cubic metre allowance on a terrace or 50 on a semi, with no dormer facing the road, is permitted development, confirmed with a Lawful Development Certificate from your borough. Inside Brockley, Telegraph Hill, Blackheath, Greenwich, Camberwell Grove or the Dulwich estate a dormer needs a householder planning application; a rooflight loft usually does not. The council has the final say.
How much does a loft conversion cost in south east London?
From £32,400 inc. VAT (£27,000 + VAT) for a rooflight loft, £56,400 inc. VAT (£47,000 + VAT) for a rear dormer, £58,800 inc. VAT (£49,000 + VAT) for an L-shaped dormer and £60,000 inc. VAT (£50,000 + VAT) for a hip-to-gable, design and build at economy specification. The final figure follows the survey and the drawings.
Which loft conversion suits a Victorian terrace in Lewisham or Southwark?
A rear dormer for one room, or an L-shaped dormer that adds a second dormer over the rear outrigger for two rooms or a room and a full bathroom. On most terraces a rear dormer fits inside the 40 cubic metre allowance; a full-length L-shape can exceed it and is sized to what is left, or taken through a householder application.
Check your own house
Not sure whether your project needs planning permission? Enter your postcode and tick what you want to build — about two minutes, free, and the from-price for each part that qualifies appears on screen and in your inbox.
To talk through a loft anywhere in south east London, book a free 30-minute consultation call with LCCL Construction on 020 8037 7332, or get an instant estimate in about two minutes. For extensions on the same houses, see rear extensions in Brockley SE4.
One team, one contract, one point of contact — from first sketch to handover.
%2C%20founder%20of%20LCCL%20Construction.jpeg)
