Barnet loft conversion plans, £589 in total
A rear dormer on a Finchley semi is often permitted development; the same dormer in a Barnet conservation area never is. We measure the roof, work out which you have, and draw for that route.
- £439 drawings + £150 survey (£589 total)
- Roof volume calculated
- Certificate or full application
What do loft conversion plans cost in Barnet?
£589 with us: £439 for drawings and submission and £150 for the survey of the roof and the floor below, with no VAT to add. Barnet Council’s fee, for a certificate or an application, is paid to the council.
Your Barnet loft set
- A survey of the roof void, ridge height, stair position and the landing below
- A cubic-volume calculation of the new roof space against the Class B limit
- Existing and proposed floor plans, elevations, a section and roof plans
- An early view on whether Barnet will want a preliminary bat roost assessment
- Submission, either as a lawful development certificate or a householder application
Certificate or application: the Barnet test
Under Class B, a roof enlargement is permitted development if it adds no more than 40 m³ on a terrace or 50 m³ on other houses, stays below the ridge, keeps back about 0.2 m from the eaves and does not sit on a front roof slope facing the road. It is never permitted development on article 2(3) land, which includes conservation areas.
Barnet has 10 conservation areas covered by or with Article 4 directions in force (Barnet conservation areas). For example, a hip-to-gable and rear dormer in Mill Hill Village or Monken Hadley is a householder application, while the same scheme on a terrace in Cricklewood may suit a certificate.
Bats, roof plans and the rest of Barnet’s list
Barnet’s validation list says proposals involving complete or partial removal of a roof will require a preliminary bat roost assessment (Barnet requirements). Most dormers open the roof, so we raise it at the quote stage; the assessment itself is carried out by an ecologist and is not part of our fee.
The same list asks for roof plans, a scale bar on every sheet, a drawing number and title, north shown, and no “do not scale” note. Electronic files must be PDFs no larger than 20 MB each.
Timing and CIL for a Barnet loft
A householder application has an 8 weeks statutory period, and Barnet decided 1,081 of 1,136 householder cases within it in the year to June 2026. A certificate follows its own timetable.
Barnet’s residential CIL is £300 per square metre for permissions from 1 April 2022 (Barnet CIL), but a loft that adds less than 100 m² is outside it under regulation 42.
Barnet lofts: the figures
- 1081 of 1136
- Barnet Council householder applications decided within 8 weeks in the year to June 2026, out of all it decided (prior approvals not counted). MHCLG live table PS2, planning application statistics by district, July 2025 to June 2026 (GOV.UK)
- 40 m³ / 50 m³
- Extra roof volume allowed under permitted development: 40 m³ on a terraced house, 50 m³ on any other house. GPDO 2015, Schedule 2, Part 1, Class B: additions to the roof (legislation.gov.uk)
- 0.2 m
- How far, as far as practicable, a permitted dormer should sit back from the eaves. GPDO 2015, Schedule 2, Part 1, Class B: additions to the roof (legislation.gov.uk)
- 10
- Barnet conservation areas covered by, or with, Article 4 directions. Barnet Council conservation areas and Article 4
- Bat roost
- Barnet requires a preliminary bat roost assessment where a roof is wholly or partly removed. Householder application requirements (Barnet Council)
- 20 MB
- Largest file size Barnet accepts for each electronic document, in PDF. Householder application requirements (Barnet Council)
- £300 per m²
- Barnet’s residential CIL for permissions granted from 1 April 2022. Barnet Council: CIL rates from April 2022
- £72.73 per m²
- The Mayor of London’s CIL in Barnet (band 2) for permissions granted in 2026, owed only when a scheme is liable for CIL in the first place. Mayoral CIL: annual rate summary for 2026, Table 1 (Greater London Authority)
- 100 m²
- Floor space below which a loft conversion is exempt from CIL. Community Infrastructure Levy Regulations 2010, regulation 42 (legislation.gov.uk)
Barnet loft questions
Can I do a dormer loft in Barnet without planning permission?
Often, if the house is not in a conservation area and the new roof space is within 40 m³ (terrace) or 50 m³ (other houses). We calculate the volume from the survey and recommend a certificate where it fits.
Will Barnet ask for a bat survey?
Its list requires a preliminary bat roost assessment where a roof is wholly or partly removed, which describes most dormers. We tell you early so it can be booked.
Does a Barnet loft pay CIL?
Not if it adds under 100 square metres, which almost every loft conversion does.
How long does Barnet take on a loft application?
The statutory period is 8 weeks, and Barnet met it for most householder cases in the year to June 2026. We cannot promise a date.
Other services people book with this one
Find your Barnet loft route
Send the address and a photo of the roof from the garden. We say whether it is a certificate or an application and fix the fee.