The full-width rear dormer, London's most-built loft form. We settle the planning or permitted-development route for your Bexley address first, then draw the building regulations set, size the steel and serve the party wall notices.
For Bexley homeowners in 1930s semi-detached dominates; Victorian cottages in Bexley Village and Crayford; post-war estates in Thamesmead and Erith, a rear dormer drawings package is the full measured-survey-to-submission drawing set London Borough of Bexley needs in order to determine an application: existing and proposed plans, elevations and sections at 1:100 and 1:50, a location and site plan, and the supporting statements the case officer asks for.
Prepared and reviewed by the chartered technologist team at Architectural Drawings London — MCIAT chartered, £2m PI insured.Last reviewed 2026-08-03.
London's most popular loft type — the full-width rear dormer. Planning or Permitted Development route assessed for your Bexley property, building regulations, structural steelwork and Party Wall notices.
Housing stock in Bexley: 1930s semi-detached dominates; Victorian cottages in Bexley Village and Crayford; post-war estates in Thamesmead and Erith.
Character: Outer south-east London suburban; very permissive planning environment; strong PD uptake for extensions and loft conversions.
Nothing gets quoted until we have tested whether the dormer qualifies for permitted development: the 40 cubic metre allowance on a terrace or 50 on a semi or detached house, whether an Article 4 direction covers the address, conservation area status, and how much of that allowance previous owners have already spent.
If the dormer is permitted development, we put it beyond doubt with a Lawful Development Certificate. If it is not, the submission becomes a full planning application, design and access statement included.
Flat roof, full width, materials answering the existing house, cheeks clad to match the roof covering, and the whole thing held in from the party walls — the form Bexley approves with the least argument.
Part B fire escape (protected staircase, fire doors, smoke alarms), Part K staircase, Part L insulation, Part E acoustic separation.
The steel ridge beam, whatever support the purlins want, the dormer's own framing, a strengthened floor: a chartered engineer puts a signature on all of it for Building Control.
A rear dormer on a Bexley terrace usually means cutting steel into the wall you share with next door. The Party Wall etc. Act 1996 calls that section 2 work, and it needs a section 3 notice served two months before anything starts. Excavation near a neighbour's foundations is the section 6 case, and it does not arise on a roof at all. We draft and serve the right notice, then run the process from there.
Single planning or regs submission.
Planning + building regs + structural.
Listed, conservation, complex sites.
Move the controls for an indicative figure. It anchors your budget — it is not a quote. Every project is priced after a free survey.
Build costs are separate and quoted by your contractor. See our published fees.
The Bexley districts we build dormers in, the stock each one holds, and the authority validating the work there. Statutory England rates for 2026 are what the table lists; none of those amounts is our fee.
| Postcode | Area | Dominant stock | What it means for a rear dormer |
|---|---|---|---|
| DA6 | Bexleyheath | 1930s semi-detached | Bexleyheath fills DA6, so the council validates every rear dormer submitted from a DA6 address. |
| DA7 | Bexleyheath / Barnehurst | 1930s semi-detached | DA7 takes in Bexleyheath and Barnehurst. The council handles the dormer, and officers read it against the DA7 conservation-area map. |
| DA8 | Erith | Victorian terraces, post-war estates | Erith has DA8 to itself, which means a rear dormer there goes to Bexley Council and nowhere else. |
| DA14 | Sidcup | 1930s semi-detached, Edwardian villas | A rear dormer at an DA14 address in Sidcup is determined by Bexley Council under its own Local Plan policies for Sidcup. |
| DA16 | Welling | 1930s semi-detached | Welling occupies DA16 alone, making Bexley the deciding authority for any rear dormer raised from that district. |
| DA17 | Belvedere | 1930s semi-detached, post-war flats | Belvedere sits wholly inside DA17, so every rear dormer application arising there is Bexley's to determine. |
| DA18 | Erith Marshes | 1930s semi-detached dominates the borough, with Victorian cottages at Bexley Village and Crayford, and post-war estates through Thamesmead and Erith. | Erith Marshes fills DA18 by itself. The dormer is Bexley's to determine, and with 18.42% of the borough's land in Flood Zone 3, a low-lying address here may need a Flood Risk Assessment submitted alongside it. |
Pitch, wall build-up and plot depth differ between Bexley Village and Thamesmead, and each difference puts a ceiling on what a rear dormer can achieve at that particular address.
How designation changes a Bexley rear dormer: Bexley Council maintains 16 conservation areas, including Crayford, Welling, Bexley Village. Inside any of them a Bexley rear dormer cannot rely on permitted development, and the route becomes a £548 householder application determined in 8 weeks rather than a £249 prior approval in 6 weeks. Bexley Village sets the tone for Bexley casework.
No blanket Article 4 over Bexley: Bexley Council has not withdrawn permitted development across Bexley, so a rear dormer outside a Bexley conservation area usually keeps it. The £274 Lawful Development Certificate is still the document a DA1 owner wants on file.
The building fabric around Bexley: 1930s semi-detached dominates; Victorian cottages in Bexley Village and Crayford; post-war estates in Thamesmead and Erith. Outer south-east London suburban; very permissive planning environment; strong PD uptake for extensions and loft conversions. A rear dormer in Bexley is scoped against that stock first, because it decides whether the scheme runs as permitted development, a £274 Lawful Development Certificate, or a full £548 application to Bexley Council.
Sources for this Bexley rear dormer page: borough policies maps and conservation-area registers (2025–26), Royal Mail postcode district boundaries, the Town and Country Planning (Fees for Applications) (England) Regulations, the Town and Country Planning (General Permitted Development) (England) Order 2015 as amended, and the Party Wall etc. Act 1996.
The questions Bexley owners send us about rear dormer drawings, answered from this borough's own record of decisions.
Start a free quote →Most Bexley loft conversions do qualify as permitted development under the standard householder allowances : a terrace gets 40 cubic metres and a semi-detached house 50, with matching materials and 20cm held back from the eaves. Flats fall outside that, so does anything within a conservation area, and so does a listed building; each needs full planning instead. Of the loft forms that stay inside those rights, the full-width rear dormer is far and away the most built here — provided volume, materials and setback all hold up. We check each of those before committing to a route.
Two lines to budget. The architectural package is ours: drawings, building regulations and structural calculations at one fixed figure. The build is the other, shifting on access, on floor area and on how the fit-out is specified; an en-suite brings plumbing runs and a drainage connection that were not there before. See our fees.
A full-width rear dormer here typically returns between 15 and 25 square metres of habitable floor — enough for one double with an en-suite off it, or a pair of single rooms. Its flat roof means full standing height wall to wall, which a rooflight-only conversion never manages, since that stays boxed in by the pitch it was cut into.
Rear dormers inside a designated area here generally require planning permission in full, since designation restricts the permitted development rights that would otherwise apply. The dormer faces the garden rather than the street, though, and officers weigh it accordingly — considerably more kindly than they weigh a front dormer or a mansard. The borough's wider record supports the point: 91.7% of householder decisions were grants.
On site, a standard Bexley rear dormer takes 8 to 12 weeks to build. Our own drawings take 3 to 5 weeks, instruction to submission, with Building Control approval adding 2 to 4 more. From the first survey to moving in, call it four or five months.
If your property sits on a boundary, here are the neighbouring options.
Bexley refuses roughly one householder application in twelve — 237 of 2,859, or 8.3%, where the 33 boroughs pooled sit at 17.0%. Its minor development refusals run close to three times that: 162 of 662, 24.5%, a shade above the London figure of 22.1% (MHCLG planning statistics, retrieved 1 September 2026). A rear dormer falls squarely on the forgiving side of that split. One chartered team draws it, engineers it and submits it.
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