Most people asking this question want a straight answer, not a range so wide it tells you nothing. So here it is upfront.
A loft conversion in South London typically costs between £40,000 and £80,000 in 2026, depending on the type of conversion, the size of your roof space, and the level of finish. That covers the majority of projects Lordans Lofts has carried out across the area, from Velux jobs in Carshalton to full dormers in Croydon and Sutton.
London prices run higher than the national average. Loft conversion costs in London average £50,000 to £90,000, with South London generally toward the lower end of that range compared to central and west London.
What Type of Loft Conversion Do You Need?
The type of conversion is the single biggest factor in your price. These are the three most common in South London.
Velux (Roof Light) Conversions
The most affordable route. No changes to the roofline. You’re adding skylights and insulating the existing roof slope. Works well on houses with adequate existing pitch and enough head height to start with.
For the London and Surrey area, a realistic budget for a Velux conversion in 2026 starts at approximately £40,000. Simpler projects with high existing headroom can come in below that.
Most Victorian and Edwardian terraces in Wallington, Carshalton, and Sutton will support a Velux conversion without planning permission, provided it falls within permitted development limits. Worth confirming with a specialist before assuming.
Dormer Conversions
A dormer extends outward from the roof slope, adding a vertical wall and providing proper standing height and usable floor space. The difference between a cramped void and a full room is significant.
Dormer conversions in London typically cost between £50,000 and £85,000 in 2026. The range reflects differences in roof structure, party wall complexity, and finish level.
South London’s mix of 1930s semis and Victorian terraces suits rear dormers particularly well. You gain space without significantly altering the house’s street-facing appearance.
Hip-to-Gable and L-Shaped Dormers
These are larger, more structural jobs. A hip-to-gable conversion rebuilds the end of a hipped roof to create a vertical gable wall, common on semi-detached properties across Sutton, Cheam, and Epsom. An L-shaped dormer, well-suited to Victorian terraces with a rear outrigger, combines two dormer volumes into a single connected space.
Hip-to-gable conversions in London run from £55,000 to £90,000. L-shaped projects at the upper end of that range or above, depending on size.
Both types may require planning permission. Lordans handles the design drawings and planning application as part of the full project.
What Makes the Price Go Up or Down?
Two projects at the same headline figure can end up very different in scope. These are the variables that move the needle most.
Head height. Building regulations require a minimum usable height of 2.2 metres. If your existing loft falls short, structural work is needed to bring it up to standard. This is more common on lower-pitched roofs, which are found in parts of South London’s 1950s and 1960s housing stock.
Access stairs. A proper fixed staircase is non-negotiable for a habitable room. The design, straight, dog-leg, or space-saving, affects both cost and how much floor space you lose on the level below.
Structural work. Steel beams, changes to load-bearing walls, and party wall agreements all add to the total. Party wall agreements in London typically cost £1,500 to £3,000 per neighbour when surveyors are involved, which is relevant for most terraced and semi-detached properties in South London.
Scaffolding and access. Scaffolding for a standard 8- to 12-week build typically costs £5,000 to £9,000. Narrow South London streets and restricted parking can add logistical costs that don’t always appear in initial quotes from less experienced contractors.
Finish level. The structural shell, insulation, first-fix electrics, plasterboard, and plastering are typically included in the Lordans project price. Flooring, en suite fittings, joinery, and decoration are quoted separately. Some clients handle that part themselves; others ask Lordans to coordinate the whole thing.
Planning. Permitted development covers most rear dormers. Front-facing changes, conservation areas, and listed buildings require full planning permission. Lordans advises at the survey stage, which applies to your property.
What Does Lordans Include?
A common source of confusion when comparing quotes is scope. With Lordans, the project price covers initial design and architectural drawings, structural calculations, liaison with the building inspector and sign-off, carpentry, roofing, insulation, electrics to the first-fix stage, and plastering.
Mark Lordan and the team manage the project from the first survey through to the building control certificate. You won’t be chasing trades or managing subcontractors yourself. That’s how Lordans has worked for 18 years across South London and Surrey, with full project management and consistent communication from the same team throughout. It’s the reason 90% of enquiries come through word of mouth.
“Very impressive from start to finish. The building team were so efficient that the work was done amazingly quickly and to a very high standard. All the tradesmen used were also excellent.” — Mr & Mrs Scally, Epsom, Surrey.
How Long Does a Loft Conversion Take?
Most Velux and dormer projects take 6 to 10 weeks from the start of groundworks. Larger hip-to-gable or L-shaped jobs typically take 10 to 14 weeks. That clock starts after planning approval (where required) and structural drawings are signed off, so allow a few weeks of pre-build lead time when planning around school terms.
Lordans will give you a realistic programme at the outset, not an optimistic one.
Frequently Asked Questions
Do I need planning permission for a loft conversion in South London?
Most rear dormer conversions fall under permitted development across South London boroughs. Properties in conservation areas, those that have already used their permitted development allowance, or houses in certain parts of Croydon and Sutton, may need full planning permission. Lordans checks this at the survey stage. You won’t be left to figure it out yourself.
Can I add a bathroom to my loft conversion?
Yes. An en suite is the most common addition and typically adds £5,000–£8,000 to the project, depending on the specification. Lordans can coordinate the plumbing and bathroom fitting as part of the wider project if needed.
Will a loft conversion add value to my home?
Industry data consistently shows that a well-executed loft conversion adds 15% to 25% to the value of a property, and in some parts of London and the South East, the return can be even higher. That said, value uplift varies by location and market conditions. For most families, the extra living space is the primary reason to proceed; the increase in value is a welcome side effect.
What if my roof space isn’t suitable?
Lordans checks head height and structural suitability at the initial survey. If the roof isn’t viable as-is, there are often ways to make it work, but that conversation happens before any money changes hands.
How do I compare quotes accurately?
Make sure every quote covers the same scope: drawings, structural calculations, building control, carpentry, roofing, insulation, first-fix electrics, and plastering. A lower headline figure that excludes several of those items is not a cheaper job.
Get In Touch
To find out what your loft conversion would cost in 2026, call Lordans Lofts on 0333 207 4233 or use the contact page. Mark and the team cover South London, Surrey, and Kent, and are happy to arrange a site visit at a time that works for you.