Dormer loft conversion and loft extension planning in Sidcup
A dormer loft conversion in Sidcup needs no planning application if it stays within 40 cubic metres on a terraced house, sits back 0.2 metres from the eaves and no Article 4 direction removes the right. Where you do apply, Bexley granted 95% of householder decisions. Our drawings start at £695.
Fixed fee from £495 drawings + £200 survey (£695 total) · all prices
Prefer to talk it through?
Three checks before you pay for a design
First, the volume. Class B of the General Permitted Development Order allows 40 cubic metres of added roof space on a terraced house. Second, the set-back: the new roof must sit at least 0.2 metres in from the eaves, measured along the slope.
Third, the street. A house in a conservation area, or one covered by an Article 4 direction, loses the right and needs an application. Our planning permission guide for loft conversions walks through each check in order.
A certificate for the permitted route
Some Sidcup owners who qualify ask the council to confirm it. Our analysis of the MHCLG planning application statistics (table PS1) counts 586 certificates of lawful development decided by Bexley over the eight quarters to mid-2026.
A certificate costs extra and the dormer can be built without one. Its value is a written record for a future sale. The certificate guide sets out the trade-off.
The national register, analysed from the MHCLG Planning Data Platform, lists 31 conservation-area entries for Bexley.
If you need a full application
Our analysis of the same statistics (table PS2) shows Bexley granted 95% of its 877 householder decisions in the latest four quarters, and, rounded, decided 100% of householder cases that were not prior approvals within eight weeks. The Bexley planning permission page covers the application route.
Our analysis of the Planning Inspectorate casework database counts 157 householder appeals decided for the borough between 2021 and 2026, of which 34% were allowed.
Mapped designations in the borough
The national register, analysed from the MHCLG Planning Data Platform, lists 31 conservation-area entries for Bexley. It may be incomplete, so use the council's own map for DA15 as the final check.
What we draw, and the price
A rear dormer starts at £695 and an L-shaped dormer at £745. Drawings are ready in 7 days and redraws are free until approval.
Once the roof is settled, the new rooms need layouts, which our floor plans for Bexley cover. Our guide to how long a loft conversion takes helps you plan the build.
Sources
Every figure on this page, where it comes from and a link to the original.
| Figure | Source | Link |
|---|---|---|
| £695 | DrawingsDirect starting fixed fee for rear dormer loft conversion permitted development drawings, from the published price list | drawingsdirect.co.uk |
| £745 | DrawingsDirect starting fixed fee for L-shaped dormer loft conversion permitted development drawings, from the published price list | drawingsdirect.co.uk |
| 40 cubic metres | GPDO 2015 Sch 2 Pt 1 Class B.1(d)(i): roof additions may add up to 40 cubic metres to the roof space of a terrace house (source wording: "40 cubic metres in the case of a terrace house") | www.legislation.gov.uk |
| 0.2 metres | GPDO 2015 Sch 2 Pt 1 Class B.2(b): a roof enlargement must be set back not less than 0.2 metres from the eaves, measured along the roof slope (source wording: "not less than 0.2 metres from the eaves") | www.legislation.gov.uk |
| 877 | Our analysis of MHCLG planning application statistics, table PS2 (district open data table) (released 24 Sep 2026, quarters to 2026 Q2) | www.gov.uk |
| 95% | Our analysis of MHCLG planning application statistics, table PS2 (district open data table) (released 24 Sep 2026, quarters to 2026 Q2) | www.gov.uk |
| 100% | Our analysis of MHCLG planning application statistics, table PS2 (district open data table) (released 24 Sep 2026, quarters to 2026 Q2) | www.gov.uk |
| 157 | Our analysis of Planning Inspectorate Casework Database (released 1 Oct 2026 (Casework Database 2609)) | www.gov.uk |
| 34% | Our analysis of Planning Inspectorate Casework Database (released 1 Oct 2026 (Casework Database 2609)) | www.gov.uk |
| 31 | Our analysis of MHCLG Planning Data Platform conservation-area and article-4-direction datasets (bulk snapshot retrieved 14 Aug 2026) | www.planning.data.gov.uk |
| 586 | Our analysis of MHCLG planning application statistics, table PS1 (district open data table) (released 24 Sep 2026, quarters to 2026 Q2) | www.gov.uk |