Double-storey extension drawings in Brent from £905
Kilburn, Willesden, Wembley and Harlesden: Brent’s 2025 SPD allows a full-width two-storey back extension, but only 3 or 4 metres deep.
£905 £755 drawings + £150 survey (£905 total), no VAT to add
Prefer WhatsApp? Send us a message · +44 7592 201353
The short answer
Brent’s Residential Extensions and Alterations SPD, adopted on 16 January 2025, lets a two-storey rear extension run the full width of your original home as long as it is no more than 3 metres deep on a terraced or semi-detached house and 4 metres on a detached one. It must stay inside the 45 degree line, and its ridge and eaves must not rise above the original. Our fee is £755 drawings + £150 survey (£905 total), no VAT to add; the council’s fee is separate.
Double-storey extension drawings
from £905
- Drawings
- £755
- Measured survey
- £150
- Total you pay
- £905
- VAT
- None to add
- A measured survey of both floors at the back and the neighbours’ original rear windows
- The 45 degree line from the middle of each nearest habitable window, with kitchens counted as habitable
- A roof designed to stay at or below your original ridge and eaves
- Ground and first floor plans, elevations, roof plan and section to Brent’s householder list
- The route that fits submitted for you, and answers to the case officer
£755 drawings + £150 survey (£905 total). A starting fee: we confirm one fixed figure after checking your address. The council’s own fee, where there is one, is paid to the council.
Get my fixed feeHow a Brent double-storey extension runs
Limit check
We set the 3 or 4 metre limit and the 45 degree line against your neighbours’ original windows.
Survey
We measure both floors, the ridge and the eaves.
Design
You choose the layout, with roof height and route written down.
Draw and submit
We prepare the pack to Brent’s list and submit it, then answer the case officer.
Three limits in section 3.2
Section 3.2 sets three tests for any two-storey rear extension. On width, it could be up to the full width of the original home. On depth, no more than 3 metres from the original rear wall for an attached home, 4 metres for a detached one, and not beyond a 45 degree line measured from the middle of the nearest habitable-room window on a neighbour’s original rear wall. On height, no higher than the ridgeline of the original home, with eaves no higher than the original.
The SPD counts kitchens as habitable rooms and bathrooms as not. For example, a neighbour with a kitchen window close to the boundary pulls the 45 degree line in sharply, so a Willesden semi can reach 3 metres only if the neighbour’s window is set back.
Outriggers, exceptions and conservation areas
The SPD says exceptions may apply to width, depth and height, so a well-argued scheme can ask for more, though the guidance is the starting point for an officer. Extensions to an outrigger are held to 3 metres from the end wall and 3.5 metres high. Permitted development allows more than one storey only up to 3 metres and not within 7 metres of the rear boundary, so most of these are householder applications.
Brent has 22 conservation areas. Its residential Article 4 directions were designed for the street side of houses, so rear rights usually remain, but we read the one that covers your road. A heritage statement is needed in a conservation area.
Validation and CIL
Brent’s householder list asks for plans, elevations and sections at 1:50 or 1:100, and a written reason for anything left out, or the application can be made invalid.
Brent CIL is £357.14 a square metre in 2026, on 100 square metres or more of new floor space, so most double-storey extensions on a house are outside it. Mayoral CIL is in band 2.
Double-storey extensions in Brent in numbers
643 of 660
Householder decisions by Brent Council between July 2025 and June 2026 (prior approvals left out) that were made inside 8 weeks.
Source: MHCLG live table PS2, district planning application statistics, July 2025 to June 2026 (GOV.UK)
3 m / 4 m
Furthest a two-storey rear extension may project from the original rear wall: attached homes 3 metres, detached 4 metres.
Full width
A two-storey rear extension could be up to the full width of the original home if it meets the depth and height limits.
45°
Line from the middle of the nearest habitable-room window next door that a two-storey extension must not cross.
Original ridge
The height of a two-storey rear extension must not exceed the original ridgeline, nor its eaves the original eaves.
16 Jan 2025
Date Brent adopted the Residential Extensions and Alterations SPD.
22
Conservation areas in Brent, with an interactive map showing which policies apply to an address.
Source: Listed buildings and conservation areas (Brent Council)
1:50 or 1:100
Normal scale of Brent’s elevations, floor plans, sections and roof plans.
Source: Validation list for applications for householder planning permission (Brent Council)
£357.14
Brent CIL per square metre for residential permissions granted in 2026, from a £200 rate set in 2013.
Source: Community Infrastructure Levy and Section 106 (Brent Council)
£72.73
Mayoral CIL per square metre for permissions granted in 2026 in Brent, which is in band 2 (£60 when set in 2019). It applies only where CIL is due at all.
Source: Mayoral CIL: Annual CIL Rate Summary 2026 (London.gov.uk)
Questions about double-storey extensions in Brent
How deep can a two-storey extension be in Brent?
Three metres on a terraced or semi-detached home, four on a detached one, and inside the 45 degree line from the neighbour’s window.
Can it be full width?
Yes. The SPD says up to the full width of your original home, provided depth and height are met.
Which windows count for the 45 degree line?
Habitable rooms on the neighbour’s original rear wall; the SPD counts kitchens but not bathrooms.
Do I pay CIL on a double-storey extension?
Not normally. CIL arises from 100 square metres of new floor space or a new dwelling.
See what your Brent house can take upstairs
Send the address and a photo of the back. We reply with the route and a fixed fee, from £755 drawings + £150 survey (£905 total).