Wraparound Extension Drawings in Blackfen DA15
Fixed-fee, MCIAT-chartered wraparound extension drawings for Blackfen (DA15) homeowners — London Borough of Bexley validation and local constraints handled from the start.
Blackfen in DA15 is a textbook 1930s Metro-land suburb of uniform interwar semis on wide, tree-lined avenues. The bulk of our work here is single-storey rear extensions, loft conversions and hip-to-gable roof works on family semis that generally sit within permitted development.
Small conservation pockets such as The Oval and The Hollies, plus the estate's overall visual consistency, mean London Borough of Bexley looks closely at how additions read against matching neighbours, so we detail dormers and extensions to preserve the street rhythm while keeping householder schemes fast to approve.
Planning in Blackfen (DA15): what to know before you apply
No published householder Article 4 direction applies in Blackfen; the main sensitivities are the uniform interwar character and small conservation pockets including The Oval, The Hollies and the Willersley and Braundton Avenue area. Most semis away from those pockets retain full permitted development rights for rear and roof works.
Typical Blackfen housing stock
Blackfen is a classic 1930s Metro-land suburb of uniform interwar semi-detached houses laid out along broad avenues. Consistent bay-fronted, hip-roofed pairs make rear extensions, loft conversions and hip-to-gable roof works the staple projects, with continuity between matching neighbours a regular design consideration.
Streets we regularly draw for in Blackfen
Wellington Avenue · Rutland Avenue · Cavendish Avenue · Montrose Avenue
What DA15 is actually built of
Measured from 387 classified residential buildings in DA15, not from a description of the area.
Blackfen DA15 housing mix
Residential building form across the DA15 postcode district, from 387 classified buildings.
| Attached on more than one side | 42% |
|---|---|
| Attached on one side | 50% |
| Detached | 8% |
| Median building footprint | 67 m² |
| Addresses per buildingAbove about 2 means flats and maisonettes dominate | 1.04 |
| Buildings classified | 387 |
Source: Ordnance Survey National Geographic Database (derived statistics). Contains OS data © Crown copyright and database right 2026. Contains Royal Mail data © Royal Mail copyright and database right 2026. Extracted 2026-08-17.
Wraparound Extension Drawings for Blackfen (DA15) homes: the package and the process
A wraparound is assessed as one addition, so the drawings have to present it as one: a single proposed footprint with the rear depth and the side width both dimensioned, the roof drawn as it turns the corner, and the remaining garden shown on the site plan.
The corner is where the technical work sits. Two roof planes and two structural spans meet at the return, drainage has to get round it, and the internal opening is usually wide enough to need a designed frame rather than a single beam. We resolve that junction on the drawings before it becomes a question on site.
A wraparound needs both a rear garden and a side alley, which in practice means a terrace or end-of-terrace with an outrigger. Where only one of the two exists, the honest answer is a rear extension or a side return — the combined footprint has nowhere to turn the corner.
What makes a wraparound extension different from a rear or side return alone?
A rear extension adds depth at the back of the house; a side return adds width down the alley; a wraparound does both at once, so the new floor area turns the corner of the original building rather than sitting against just one wall. The result is typically the largest open-plan space a single-storey extension can deliver, but it also means more of the original external wall is removed and more of the roof is new, which raises the structural and drainage stakes compared with either extension on its own. Homeowners who start out planning a rear extension or a side return alone often move to a wraparound once they see how little extra it costs to combine the two, since much of the groundwork, roof structure and glazing is shared between them rather than duplicated.
Do wraparound extensions need full planning permission in London?
Almost always, yes. Permitted development allowances are calculated on combined additions to the original house, and a wraparound's depth plus width together generally exceed the volume and footprint limits that apply to a rear extension or side extension considered separately. A Lawful Development Certificate route is rarely viable for a genuine wraparound.
Conservation area status and Article 4 directions, common across the terraced streets where wraparound extensions are most popular, remove permitted development rights further still, so we design every wraparound on the assumption it will go through full householder planning.
Structural design for a wraparound extension
Because the new space turns a corner, the structural frame has to work as one continuous system rather than two independent extensions bolted together.
- A continuous steel or ring-beam frame carrying the roof around the internal corner where the rear and side elements meet
- A glazed roof lantern or rooflight strip often placed at the corner junction, where natural light reaches deepest into the combined plan
- Foundations for both the rear and side elements designed together, so they tie into the existing house consistently
- Bi-fold or sliding doors across the rear elevation, coordinated with the side glazing so the two elements read as one space
| Route | What it covers | Typical fee |
|---|---|---|
| Full planning permission | Required for almost all wraparound extensions given the combined footprint | Full Planning pack ~£1,600–£2,400 |
| Planning + Building Regulations (structural) | Combined pack including structural calculations for the L-shaped frame and drainage diversion | Planning + Building Regs pack ~£2,200–£3,850 |
| Rear extension alone (comparison) | Smaller single-storey addition, may qualify for permitted development | see Rear Extension Drawings, from £1,100 |
| Side return alone (comparison) | Widens the kitchen only, keeps garden depth unchanged | see Side Return Extension Drawings, from £1,400 |
Wraparound Extension Drawings in Blackfen DA15 — FAQs
How much does a wraparound extension cost to design in London?+
Does a wraparound extension always need planning permission?+
Do I need an architect for a wraparound extension?+
Will I need a Party Wall Agreement for a wraparound extension?+
How long does it take to get wraparound extension drawings?+
Do I need planning permission for an extension in Bexley?+
Can I build a bigger extension because Bexley plots are larger?+
What extra control applies in Old Bexley Village or around Danson Park?+
How long does Bexley Council take to decide?+
How much do planning drawings cost in Bexley?+
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