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?
Every loft conversion estimate is individual. The price depends mostly on the conversion type, structural complexity and finish quality, so we prepare it for your house after a free site visit rather than quoting a headline figure. The programme on site for each type:
| Loft conversion type | Programme |
|---|---|
| Rear dormer loft conversion | 8 to 11 weeks |
| Mansard loft conversion | 10 to 14 weeks |
| Hip-to-gable loft conversion | 10 to 13 weeks |
| L-shape mansard loft conversion | 11 to 15 weeks |
The price drivers 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 costs more than a single-dormer single-bedroom loft in a narrow Victorian terrace. Conservation area work costs more because of consent timescales and specification controls.
We give a written rough order-of-magnitude budget within three working days of a free site visit, and a fixed, fully itemised quote once the layout and finishes are agreed. 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. To book a free site visit, 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 |
| 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
In conservation areas (Leytonstone E11, Brockley SE4, parts of Hackney, Highgate, Holland Park, Notting Hill) a loft conversion that enlarges the roof is not permitted development and needs planning permission. Other roof changes, such as rooflights or re-roofing, can still be permitted development, but Article 4 directions and listed status can remove that, so we check them for each house. Our conservation area planning guide compares every type of work inside and outside a conservation area. 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 carries the applicable council 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. Our permitted development guide sets out the loft limits and how the certificate works.
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. Our party wall guide explains which work needs notice and how surveyors and awards work.
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.
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?
A loft conversion adds a bedroom and often an en-suite, which usually raises the market value of a London terrace. How much depends on the street, the house and the local market, so we recommend asking a local estate agent for a valuation before you commit.
What is the cheapest type of loft conversion?
There is no single cheapest type: every estimate is individual. A rooflight-only (Velux) conversion keeps the existing roof shape and can suit a loft that already has enough headroom. A rear dormer adds usable headroom and floor area, can use permitted development rights where they apply (no planning application), and its cheeks can be tile-clad to match the roof. After a site visit we compare the options that are viable for your house in the estimate.
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 to the conversion cost because of the structural rework needed. We assess feasibility on a free site visit before quoting.
Project examples for this service
Compare the scope, location and photographs of each example before discussing your own project.
Ready to discuss your project?
Free initial site visit. Every estimate is individual, and scope, specification and price are agreed with you before work starts. Written rough-order-of-magnitude budget within three working days.
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