A London loft conversion usually needs one set of drawings for the council and a second, more detailed set for building control. This page shows what is in each set for every loft type, which route a London house takes, and a worked volume calculation you can test your own roof against.
(£565 if you supply measured drawings)
Loft conversion with rooflights (Velux)
Fixed in writing after a free assessment of your property. Council planning fees are separate.
Every price is the total you pay. Checked 24 October 2026.
Every loft type needs the same core sheets. What changes is the route and the sheet that carries the risk. The route column describes the usual position under the permitted development order (GPDO 2015, Schedule 2, Part 1, Class B), subject to the tests in the route table below.
| Loft type | Usual route | Sheet that carries the risk | Limit to check |
|---|---|---|---|
| Rooflights only | Class C of the same Part (no volume count) | Roof plan and section showing the rooflight standing no more than 0.15 m off the slope | Protrusion of 0.15 m or less from the original roof slope (Class C, C.1(b)) |
| Rear dormer | Certificate of lawful development if inside Class B; otherwise a planning application | Section through the dormer with the new volume calculated and the 0.2 m eaves set-back dimensioned | 40 m3 terrace, 50 m3 other houses; no part higher than the existing ridge |
| Hip-to-gable | Usually Class B, often combined with a rear dormer | Side elevation and roof plan showing the new gable; volume added by the infill | Same volume cap, counted together with any dormer. The 0.2 m eaves condition does not apply to the hip-to-gable part |
| L-shaped dormer over an outrigger | Usually Class B where it joins the original roof to a rear extension or rear outrigger | Roof plan showing both dormers and the join; one volume total | Exceptions in B.2(b)(i) and (ii) for an enlargement that joins the original roof to the roof of a rear or side extension. B.4(b) and the MHCLG technical guidance treat an original outrigger as a rear extension |
| Mansard | Usually a planning application: the full-width steep face is hard to fit inside Class B | Front and rear elevations plus a section with materials annotated | Class B tests still apply; the council's own roof-extension guidance usually decides the outcome |
| Loft in a flat or maisonette | Full planning application (no householder route) | Existing and proposed elevations with the neighbouring flats and any shared structure | No householder permitted development under Part 1, including Classes B and C: a flat is not a dwellinghouse under article 2(1) of the order |
Source: GPDO 2015, Schedule 2, Part 1, Classes B and C and article 2, read 14 October 2026. 'Usual route' describes the common position only. Each house is tested against the whole of B.1 and B.2.
The planning or certificate set shows what is being built. The building regulations set shows how. Scales below are standard practice on our drawings. Councils publish their own validation lists, so check yours before submitting.
| Drawing | Typical scale | Certificate or planning stage | Building regulations stage |
|---|---|---|---|
| Location plan | 1:1250 | Site edged red, north point, two named roads | Not re-issued in most cases |
| Block plan | 1:200 or 1:500 | Footprint and boundaries; confirms the roof change sits inside the plot | Used for drainage and access context |
| Existing floor plans and roof plan | 1:50 or 1:100 | As built, with the roof space measured | Starting point for structural survey |
| Proposed floor plans | 1:50 or 1:100 | New loft floor, stair position and head heights | Stair, escape window and door positions fixed |
| Elevations, existing and proposed | 1:50 or 1:100 | Dormer or gable size and materials annotated | Cladding, insulation and fire details cross-referenced |
| Section through loft and stair | 1:50 | Head heights, ridge level, eaves set-back, volume check | Floor, roof and wall build-ups at 1:20 or larger |
| Structural layout | 1:50 | Not required for the certificate or planning decision | Joist, steel and padstone positions with calculations |
A certificate application must carry a plan to an identified scale with a north point, evidence verifying the application and a statement of the applicant's interest in the land (DMPO 2015, article 39(2)). The scales listed are our working practice, not statutory scales.
A house within every Class B limit does not need planning permission, and a certificate of lawful development is the optional way to prove it. Anything else needs an application, and the application type depends on whether the property is a house or a flat.
| Situation | Route | Council decision period | What it means for the drawings |
|---|---|---|---|
| House, outside designated land, no Article 4 direction or planning condition removing Class B, within 40 or 50 m3 and the other limits | Permitted development; certificate of lawful development optional | 8 weeks from a valid certificate application (article 39(10)), unless you agree a longer period in writing | Dimensioned section and volume sums matter most, because the council tests the drawings against the order |
| House, but volume, ridge height, front slope or a balcony breaks a Class B limit | Householder planning application | 8 weeks for a non-major application (article 34(2)(b)), unless you agree a longer period in writing | Design statement and the council's roof-extension policy matter more than the volume count |
| House on article 2(3) land (this includes conservation areas) | Householder planning application: Class B is not available (B.1(f)) | 8 weeks, as above | Heritage and street views, because the council judges the roof against the character of the area |
| House where an Article 4 direction removes Class B | Householder planning application | 8 weeks, as above | The direction wording decides which roof alterations it covers: read the council's own notice |
| Flat or maisonette | Full planning application (not a householder application) | 8 weeks for a non-major application, unless agreed otherwise | Shared structure, neighbouring flats and notice to the freeholder and other owners (DMPO article 13) are normally part of the pack |
| Listed building | Listed building consent for works affecting its character (Listed Buildings Act 1990 s.7), plus planning permission unless the work is permitted development | 8 weeks for each from a valid application, unless agreed otherwise in writing | Heritage statement and detailed roof construction drawings |
Sources: GPDO Class B, B.1(f) and B.3; DMPO articles 34 and 39; TCPA 1990 s.192; Planning Portal loft conversion page. Read 14 October 2026. The eight-week periods run from a valid application. Listed buildings carry their own consent rules: ask the council.
This example is arithmetic, not a real job, and the dimensions are assumed. Take a two-bedroom Victorian terrace outside any conservation area, with no earlier roof extension. The owner wants a full-width rear dormer and a smaller dormer over the rear outrigger.
The main dormer is 4.6 m wide with a vertical face 2.3 m high. On a roof pitched at about 38 degrees the flat roof meets the slope 2.9 m back, so each cheek is a right triangle of half 2.3 by 2.9, or 3.34 m2. Times the 4.6 m width, the added volume is 15.3 m3.
The outrigger dormer is 2.4 m wide with a 1.9 m face and a 2.4 m run, so a cheek of 2.28 m2 and 5.5 m3. The two together add 20.8 m3, against a cap of 40 m3 for a terrace house. About 19 m3 of the allowance is left.
Volume is only one test. The drawings must also show the 0.2 m eaves set-back on the main dormer (so far as practicable), the ridge left untouched, no balcony, matching materials, and any side window obscure-glazed and non-opening unless the opening part is more than 1.7 m above the floor. A terrace house for this purpose means a dwellinghouse in a row of three or more; an end-of-terrace in such a row takes the 40 m3 limit too. How the cubic content is counted is set out in our dormer loft conversion planning permission guide.
Route for this house, assuming no Article 4 direction or planning condition removes Class B: an optional certificate of lawful development, which the council has eight weeks from a valid application to decide. If the same house stood in a conservation area, Class B would not apply and the same drawings would go in with a householder application instead. The arithmetic does not change, but the question the council asks does.
The Class B limits are national, so the volume cap is the same in every borough. What differs is how many streets sit on designated land and how councils decide householder applications. These eight boroughs decided the most householder applications in 2025-26.
| Borough | Householder decisions 2025-26 | Approved | Conservation areas (national register) |
|---|---|---|---|
| Bromley | 1,538 | 79.0% | 69 |
| Barnet | 1,439 | 82.2% | 16 |
| Richmond upon Thames | 1,362 | 81.7% | 85 |
| Hillingdon | 1,184 | 90.2% | 42 |
| Redbridge | 1,050 | 81.5% | 19 |
| Havering | 1,019 | 82.8% | 11 |
| Enfield | 999 | 83.1% | 24 |
| Ealing | 993 | 87.7% | 31 |
Sources: MHCLG planning application statistics PS1 and PS2, 2025 Q2 to 2026 Q1, 'other' householder developments (London: 24,758 decisions, 85.6% approved); MHCLG Planning Data Platform conservation-area register, fetched 15 August 2026. The register counts differ from some councils' own lists (Ealing's pages say 30), so use the borough page and the council's own list for your street.
These are common drawing errors that stall loft applications.
A certificate or planning permission says the roof alteration may be built. It does not approve the construction. Floors, stairs, escape, fire separation and insulation need building regulations approval whichever planning route you take, and that set is prepared from the approved drawings. Our building regulations drawings page sets out what goes in it, and our loft conversion building regulations guide covers the loft specifics.
Where steel or a new floor bears on a wall shared with a neighbour, the Party Wall etc. Act 1996 can apply separately from both planning and building control. That is a different statutory regime with its own notice periods: see party wall surveying in London.
Often not, if the house stays inside every Class B limit and is not a flat or on designated land. The full test, letter by letter, sits in our guide to planning permission for a loft conversion, with the certificate explained in our lawful development certificate guide.
Tell us about your project and get a fixed, no-obligation quote back within one working day. If you don't need planning permission at all, we'll tell you that too — for free.
We draw lofts the way your borough's planners expect to see them, and test every dormer against the Class B volume cap before the drawings go in.
The same four steps apply to a rooflight loft and to a full mansard.
We look up whether your address sits on designated land, whether a direction removes Class B, and whether you are a house or a flat, then recommend the certificate or application route.
We measure the roof space, head heights, ridge and eaves, and draw the existing plans and section.
We draw the proposed loft to your brief and test the volume and the other Class B limits on paper.
We submit the certificate or application, deal with the case officer, and revise the drawings free until the council decides.
You need a location plan (we draw it at 1:1250), a block plan, existing and proposed floor plans and elevations, and at least one section showing head heights, the stair and the ridge. A certificate of lawful development needs a plan to an identified scale with a north point plus evidence. Your council's own validation list adds to this, so check it before you submit.
Not when the house is outside designated land, is not a flat, and stays inside every Class B limit, including 40 cubic metres of added roof space on a terrace and 50 on other houses. Conservation areas, flats and designs that break a limit need an application. Our dedicated guide to planning permission for a loft conversion sets out each test.
A certificate of lawful development confirms the council agrees the work is lawful without planning permission, because it falls within permitted development. It is optional and decided on the legal tests, not on design merit. Planning permission is a discretionary decision on the merits. The council has eight weeks from a valid application to decide a certificate under article 39(10).
We aim to issue the drawings within seven days of the measured survey. The council then has eight weeks from a valid application to decide a planning application or certificate, unless you agree a longer period in writing. An application that is not valid does not start the clock, so complete drawings matter. Building regulations approval is a separate step.
Yes, but a rear dormer needs planning permission. Class B does not apply on article 2(3) land, which includes conservation areas, so the council decides the roof against the character of the area. Rooflights under Class C are tested differently and an Article 4 direction can still remove them, so check the council's list for your street.
Yes. Permitted development under Part 1 of the order applies to dwellinghouses, and a flat is not a dwellinghouse under article 2(1). A loft or roof extension over a flat needs a full planning application, not a householder one. You may also need the freeholder's consent under your lease.
Yes. Planning and certificate drawings show size, appearance and position. Building regulations drawings show how the loft is built: floor joists and steel, stair and escape routes, fire separation, insulation and ventilation. You need building regulations approval whichever planning route you take, and the building regulations set is prepared from the approved planning drawings.
The permitted development order sets no minimum head height. The practical question is whether the roof space gives enough floor area with usable head height once the new floor and insulation are in, and the building regulations set the stair and escape standards. A measured survey of ridge and floor levels answers it before you commit to drawings.
Sometimes. The Party Wall etc. Act 1996 can apply where steel, a new floor or alterations bear on a wall shared with a neighbour. It is separate from planning and building regulations and has its own notice periods. The notice is the owner's responsibility, so we flag it early in the programme.
A certificate is council-issued confirmation that the roof alteration would be lawful (TCPA 1990 s.192), which a buyer's solicitor may ask for when you sell. It is optional. Without it you rely on your own reading of Class B. The certificate is only as good as the drawings behind it, because the council tests the dimensions you submit.
Local drawings tuned to each council's design guidance, with live borough approval rates. Pick your area:
Loft conversion plans in Ealing from £765 inc survey 📐 SPD 4 dormer margins and the hip-to-gable rule checked first. Fixed fee, we draw and submit.
View Ealing →Loft conversion plans in Wandsworth from £765 inc survey 📐 We check where your house sits in its terrace; ends and mid-terraces differ. Fixed fee.
View Wandsworth →Loft conversion plans in Bromley from £765 inc survey 🏠 Petts Wood lost its dormer right in 2022; we check your street first. Fixed fee, we submit.
View Bromley →
Loft conversion plans in Barnet from £765 inc survey 📐 Permitted development where it applies, Barnet's 0.5 metre dormer set-ins where it does not.
View Barnet →
Loft conversion plans in Harrow — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Harrow →Loft conversion plans in Sutton — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Sutton →Loft conversion plans in Richmond upon Thames — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Richmond upon Thames →Loft conversion plans in Kingston upon Thames — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Kingston upon Thames →Loft conversion plans in Camden — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Camden →Loft conversion plans in Islington — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Islington →Loft conversion plans in Haringey from £765 inc survey 🏠 We know which of the three South Tottenham roof types fits. Fixed fee, we draw and submit.
View Haringey →Loft conversion plans in Enfield from £765 inc survey 📐 Drawn to policy DMD 13: dormers inset 500 to 750 mm from the edges. Fixed fee, we submit.
View Enfield →Loft conversion plans in Waltham Forest — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Waltham Forest →Loft conversion plans in Hillingdon — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Hillingdon →Loft conversion plans in Hounslow — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Hounslow →Loft conversion plans in Brent from £765 inc survey 📐 Drawn to Brent's 2025 SPD: full-width rear dormers, L-shapes capped at half the outrigger. Fixed fee.
View Brent →Loft conversion plans in Hammersmith and Fulham — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Hammersmith and Fulham →Loft conversion plans in Kensington and Chelsea — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Kensington and Chelsea →Loft conversion plans in Westminster — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Westminster →Loft conversion plans in Merton — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Merton →Loft conversion plans in Lambeth from £765 inc survey 🏠 Dormer type, cill and head heights checked against the Design Guide. Fixed fee, we submit.
View Lambeth →Loft conversion plans in Croydon from £765 inc survey 📍 Roof volume worked out first, since it decides if you need permission. Fixed fee, we submit.
View Croydon →Loft conversion plans in Hackney — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Hackney →Loft conversion plans in Tower Hamlets — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Tower Hamlets →Loft conversion plans in Newham — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Newham →Loft conversion plans in Redbridge — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Redbridge →Loft conversion plans in Barking and Dagenham — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Barking and Dagenham →Loft conversion plans in Havering — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Havering →Loft conversion plans in Greenwich — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Greenwich →Loft conversion plans in Lewisham — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Lewisham →Loft conversion plans in Bexley — dormer, hip-to-gable and mansard drawings submitted for you and revised free until your council approves.
View Bexley →Loft conversion plans in Southwark from £765 inc survey 📐 Dormer sizes checked against the 2025 Householder SPD before we draw. Fixed fee, we submit.
View Southwark →Answer five quick questions and get a free planning score for your exact address — instantly. Then, if you want the full picture, unlock the detailed analysis: your council's live approval rates, local precedents, constraints on your street and a step-by-step route to permission.