020 8004 4464Discuss your project

CASE STUDY · APPROVED

Single-storey wrap-around extension and porch to a semi-detached house

Allonby Gardens, Wembley · London Borough of Brent

A single-storey wrap-around extension, enclosed front porch and internal alterations were proposed to an interwar semi-detached house, followed by a householder application to regularise the extension as built with new rendering, front windows and rear decking. We prepared the design and access statements, Level 1 flood risk assessments and the drawing packages for both applications.

The completed wrap-around extension and rear decking during finishing works (Design and Access Statement, retrospective application)
The completed wrap-around extension and rear decking during finishing works (Design and Access Statement, retrospective application)

The site

The two-storey semi-detached house sits in a residential street of interwar semi-detached homes with generous gardens. It is not in a conservation area or subject to an Article 4 direction, but lies about 85 metres from a Grade II listed public house, within an SSSI impact zone and in Flood Zone 1, with a PTAL rating of 2.

The challenge

The wrap-around extension had to stay within the Residential Extensions and Alterations SPD2 limits on side extension width and rear depth while respecting the neighbouring houses. The surface water flood mapping showed a high risk of surface water flooding within 15 metres of the property, and the later application had to explain the differences between the approved scheme and what was built.

What was submitted

  1. Design and Access StatementSet out the wrap-around extension with a new bedroom, bathroom, kitchen/dining area, garage extension and enclosed porch, with the rear building line and flat roof height aligned with the neighbouring house's approved wrap-around extension. It proposed a flat roof with five rooflights and materials matched to the host building.
  2. Flood Risk AssessmentA Level 1 assessment confirmed Flood Zone 1 (annual probability of river or sea flooding below 0.1%), so the Exception Test was not required, but identified a high surface water risk (greater than 3.3% each year). It recommended flood-resilient services and fittings and SuDS following the London Plan drainage hierarchy.
  3. Design and Access Statement (retrospective application, 24/2960)Compared the approved and as-built schemes: a rear depth of 4.59 m against the approved 4 m, a 5.31 m depth against the 5 m prior approval (23/3355), and an eaves height of 3.00 m against 2.84 m, plus a 280 mm raised rear platform. It explained the change from pebble-dash to white render to match the attached house and showed similar approved extensions on the same street.
  4. Pre-existing, approved and existing elevationsShowed the white-painted rendered walls, slate tile roof to the garage and replacement white UPVC windows matching the original sizes.

Outcome

The wrap-around extension and porch (23/3238) were approved by the London Borough of Brent on 8 January 2024, and the retrospective application to regularise the extension, decking, front windows and rendering (24/2960) was approved on 18 December 2024.

From the reports

Approved and as-built front elevations showing the garage extension, white render and replacement windows (Pre-existing, approved and existing front elevations)
Approved and as-built front elevations showing the garage extension, white render and replacement windows (Pre-existing, approved and existing front elevations)

Images and findings are taken from the documents submitted with the planning application. The full application is available on the council's planning register.

YOUR NEXT STEP

Planning something similar?

Tell us about the site and what you want to achieve. We will tell you which reports the council is likely to need and what they should cost.

Call 020 8004 4464 or email info@greencodeconsultants.com.

Make an enquiry