Types of loft conversion we deliver
Mansard conversions give the maximum head height and floor area but require planning permission and are most common on Victorian and Edwardian terraces in central and inner London. L-shape mansards are the standard solution for Victorian terraces with an existing rear addition. Hip-to-gable conversions suit semi-detached and end-of-terrace properties in the suburbs (Walthamstow, Wanstead, Winchmore Hill). Dormer conversions are typically permitted development and the fastest to build.
What you get with a KRAMAN loft conversion
Architectural drawings, structural engineer calculations, party wall surveys and agreements, building control application and inspections, demolition and steelwork, new floor and ceiling joists, rafters and roof construction, insulation to current Part L standards, full electrical installation, plumbing for en-suite, plastering, joinery, decoration, flooring, staircase. Velux windows and dormer cheeks finished in matching tile or zinc. Smoke and heat alarms wired into the existing system to comply with London building regulations.
Programme
A typical L-shape mansard runs 10 to 14 weeks on site, including building control sign-off and final inspection. A standard dormer runs 8 to 11 weeks. Hip-to-gable conversions run 10 to 13 weeks. We work to a written programme agreed at contract signing and our handover includes the building control completion certificate, FENSA certificate for windows, NICEIC electrical certificate and Gas Safe boiler servicing record.
Common loft conversion postcodes we cover
East London: E10 Leyton, E11 Leytonstone and Wanstead, E14 Canary Wharf and Isle of Dogs, E15 Stratford, E17 Walthamstow. North London: N6 Highgate, N21 Winchmore Hill. South East London: SE4 Brockley, SE10 Greenwich, SE13 Lewisham. Central London: SW3 Chelsea, SW7 South Kensington, W11 Notting Hill.
How much does a loft conversion cost in London?
Loft conversion prices in London in 2026 vary mostly by conversion type, structural complexity and finish quality. Below are the bands we quote within for a standard London terrace or semi after a free site visit. These are real ranges from completed KRAMAN projects, not headline-only figures, and exclude VAT and architect fees.
| Loft conversion type | Typical London price | Programme |
|---|---|---|
| Rear dormer loft conversion | £40,000 to £65,000 | 8 to 11 weeks |
| Mansard loft conversion | £55,000 to £85,000 | 10 to 14 weeks |
| Hip-to-gable loft conversion | £45,000 to £75,000 | 10 to 13 weeks |
| L-shape mansard loft conversion | £60,000 to £90,000 | 11 to 15 weeks |
The price drivers within each band are floor area, structural steelwork, complexity of the staircase landing, en-suite specification and the finish budget (ironmongery, joinery, glazing and flooring). A loft in a wider Edwardian semi with two dormers and an en-suite will sit at the top of the band; a single-dormer single-bedroom loft in a narrow Victorian terrace will sit at the bottom. Conservation area work adds 8 to 15 percent because of consent timescales and specification controls.
We give a fixed quote after a free site visit, not before. Headline prices online almost never match the cost of the project as built because every London loft conversion has a different roof structure, party wall and staircase landing. For a fully itemised quote in writing within three working days, call 07717 778 612 or book a free site visit through the contact form.
Dormer vs mansard: which loft conversion is right for your home?
Most London terrace owners decide between a rear dormer and a mansard. Both produce a usable loft floor, but the choice depends on roof shape, planning constraints, target headroom and budget. A side-by-side comparison from twenty years of completed projects in East and South East London is below.
| Factor | Rear dormer | Mansard |
|---|---|---|
| Planning permission | Usually permitted development (terrace) up to 40m³ | Almost always required, including planning fee |
| Headroom in main bedroom | 2.1 to 2.4 metres in usable centre area | 2.3 to 2.6 metres across nearly full floor |
| Floor area gained | 18 to 28 square metres on a typical terrace | 25 to 36 square metres on a typical terrace |
| Typical cost (London 2026) | £40,000 to £65,000 | £55,000 to £85,000 |
| Programme on site | 8 to 11 weeks | 10 to 14 weeks |
| External appearance | Visible rear projection, neighbours may notice | Sympathetic to period terraces, often improves rear elevation |
| Best suited to | Narrow terraces, suburbs, budget-led projects | Wide Victorian terraces, period semis, conservation-area-adjacent streets |
Verdict by house type
- Victorian terrace in Leytonstone, Hackney or Walthamstow: a rear dormer is the fastest, cheapest and usually permitted development. A mansard gives a more impressive room but adds planning risk.
- Wide Edwardian semi in Winchmore Hill or Wanstead: hip-to-gable with a rear dormer is the dominant choice. A mansard is rare on this stock.
- Conservation-area period terrace in Brockley or Hackney: a mansard is sometimes the only option that the council will grant consent for, because rear dormers can be visible from the public realm.
- Listed property in Highgate or central London: typically neither is permitted; Velux roof glazing only is the usual outcome.
Walk through the trade-offs with us on a free site visit. We have completed both types across East London, South East London and North London, with examples in our client reviews.
Loft conversion planning permission in London
Most London terraces qualify for permitted development on a loft conversion, but the rules are tighter than homeowners often expect. Below are the headline rules under the General Permitted Development Order, written in plain English. We confirm the position with the relevant council on every project before we commit to a programme.
Volume limits
- Terraced house: 40 cubic metres of new roof volume allowed under permitted development.
- Semi-detached or detached: 50 cubic metres.
- The volume counts the entire added enclosure (dormer cheeks plus internal void), not just the bedroom floor area.
Rear dormer rules
- Cannot extend beyond the original roof plane on the front (street-facing) elevation.
- Must be set back at least 200mm from the existing eaves at the rear.
- Cladding materials must match the existing roof (tile, slate, or similar) unless the council's Article 4 direction overrides.
- No balconies, no terraces, no raised platforms higher than 300mm.
Mansards almost always need planning permission
A mansard replaces the existing roof shape, which falls outside permitted development. Planning permission is required from the local council and the application typically takes 8 to 12 weeks. We submit the application as part of the project management and our success rate is over 92 percent on first submission across Waltham Forest, Hackney, Lewisham and Camden.
Conservation areas
Conservation areas (Bushwood E11, Brockley SE4, Hackney Square, Highgate Village, Holland Park, Notting Hill) usually have Article 4 directions that remove permitted development rights entirely for loft conversions. Planning permission is required for any external change. Specification is also tighter — natural slate, traditional dormer detailing, no flat-roof boxes visible from the public realm.
Lawful Development Certificate
Even when the loft conversion is plainly permitted development, we recommend applying for a Lawful Development Certificate (LDC). The certificate costs about £103 (half a planning application fee) and gives a binding determination from the council that the work is lawful. It protects future resale value and is increasingly demanded by mortgage lenders. We submit the LDC application alongside the building control application.
Party wall agreements
Terrace and semi-detached loft conversions almost always require party wall agreements with each adjoining owner under the Party Wall etc. Act 1996. The notice period is two months. We work with party wall surveyors who specialise in residential terraces in our catchment and can typically conclude an agreement in 6 to 10 weeks from notice.
Loft conversion timeline: how long does it take?
A standard London loft conversion runs 8 to 14 weeks on site, plus 6 to 12 weeks of pre-construction (drawings, party wall, planning or LDC, building control submission). The phase breakdown below is taken from completed KRAMAN projects across East and South East London on Victorian and Edwardian terraces.
| Phase | Duration | What happens |
|---|---|---|
| 1. Drawings and consents | 2 to 4 weeks | Architect produces drawings, structural engineer issues calculations, LDC or planning submitted |
| 2. Structural & roof | 2 to 4 weeks | Steelwork, new floor and ceiling joists, rafters, roof opened up and reframed |
| 3. Weatherproofing | 1 week | Tiles or slates relaid, dormer cheeks zinc or tile, flashings completed |
| 4. First fix M&E | 1 week | Plumbing for en-suite, electrical first fix, smoke and heat alarms wired |
| 5. Insulation, plasterboard, plaster | 2 to 3 weeks | Mineral wool and rigid board, plasterboard, two-coat plaster skim |
| 6. Second fix & finishes | 2 to 3 weeks | Joinery, doors, skirting, decoration, flooring, sanitaryware, electrical second fix |
| 7. Building control & snagging | 1 to 2 weeks | Final inspection, completion certificate, snagging walkthrough |
Programme is fixed at contract signing. Weekly Friday progress photos and a four-stage payment schedule tied to actual milestones (steel in, weatherproof, plaster complete, practical completion). For a full programme on your specific property book a free site visit on 07717 778 612.
Frequently asked questions
Do I need planning permission for a loft conversion?
Most dormer and hip-to-gable conversions in London are permitted development. Mansards typically require planning permission. Conservation areas (parts of Brockley, Camden, Highgate and most of central London) almost always require planning consent. We submit planning applications as part of the project management.
Will my floor below need to be replastered?
Inevitably the existing ceiling is opened up to install new floor joists for the loft, so the room below is replastered. This is included in our quote and disclosed at survey stage so you can plan furniture removal.
Can a loft conversion be insulated to Passivhaus standard?
Yes, we have done several. Triple-glazed Velux windows, 200mm of mineral wool plus 50mm rigid insulation between rafters, internal vapour barrier and breathable membrane externally. The cost premium over standard Part L compliance is around 12 to 18 percent of the loft package.
Do I need planning permission for a dormer loft conversion?
Most rear dormer loft conversions on terraced houses in London fall under permitted development and do not require planning permission, provided the new volume stays within the 40 cubic metre limit and the dormer is set back at least 200mm from the eaves. We always confirm with the council and recommend a Lawful Development Certificate (LDC) for legal certainty at resale.
Can I live in the house during a loft conversion?
Yes for almost all loft conversions. The works are concentrated above the existing top floor with separate access via internal scaffolding from a single staircase point. Noise and dust are limited to one or two rooms at any time. The week the existing ceiling is opened up for new floor joists is the most disruptive — we recommend planning that week around school or work travel where possible.
Will a loft conversion add value to a London property?
On a typical Victorian terrace in East or South East London a loft conversion adds 18 to 25 percent to market value, almost always more than the build cost. Independent estate agent valuations after our completed projects routinely show the increase exceeds the £55k to £85k build cost by 30 to 80 percent.
What is the cheapest type of loft conversion?
A rear dormer loft conversion is consistently the cheapest format, typically £40,000 to £65,000 on a London terrace. It uses permitted development rights (no planning fee), keeps the existing roof structure largely intact, and the dormer cheeks can be tile-clad to match. A Velux-only loft conversion is cheaper still (£25k to £40k) but produces a low-ceiling space that most clients regret within a year.
Do I need a party wall agreement for a loft conversion?
Yes if the house is a terrace, semi-detached or end-of-terrace and the works affect the party wall (which almost every loft conversion does). The Party Wall etc. Act 1996 requires written notice to each adjoining owner two months before works begin. We engage a party wall surveyor as part of project management.
How much headroom do I need for a loft conversion?
Building Regulations require minimum 1.9 metres clear at the top of the new staircase. Most architects design for at least 2.3 metres in the usable centre of the loft bedroom. Below 2.0 metres of existing ridge-to-ceiling height makes a conversion borderline; below 1.8 metres it is structurally impractical. We measure ridge height on the initial site visit and confirm feasibility before any drawings are commissioned.
Can I do a loft conversion on a Victorian terrace in London?
Yes — Victorian terraces are the building type we most often convert, particularly in East London (Leytonstone, Hackney, Walthamstow) and South East London (Brockley, Lewisham). The typical conversion is an L-shape mansard above the rear addition, giving a master bedroom with en-suite and a second small bedroom or study. See our Brockley and Leytonstone project galleries for completed examples.
Can I convert a flat-roofed extension into a mansard?
Sometimes. If the existing flat roof is on a single-storey rear addition, it can occasionally be lifted to a mansard roof if planning consent is granted, but this is unusual and adds 15 to 25 percent to the conversion cost because of the structural rework needed. We assess feasibility on a free site visit before quoting.
Related projects
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