Merton, London
L-shaped dormer drawings in Merton
L-shaped dormer drawings in Merton face an unusual pairing of numbers. The council granted 92.9% of householder applications in its latest year, but only 85.2% were decided within eight weeks or an agreed extension. The grant rate is good; the programme needs room.
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How we work on l-shaped dormer drawings
Nine steps from first call to approval.
Enquiry and constraints check
We check the property against conservation areas, listed status, Article 4 directions, tree preservation orders, flood zone and planning history. We choose the right route and send a fixed quote.
Measured survey
We survey the house on one datum: rooms, levels, boundaries, drains, trees and the neighbours' windows that the 45° and 25° tests depend on.
Design options
We model the house in Revit and show you options in 3D and plan, with the planning strategy and the precedents in your street.
Design frozen
You choose an option in writing. Nothing changes after this without your say.
Independent check
A second chartered technologist checks every sheet against the council's validation checklist and the policy. A senior review signs it off before anything is submitted.
Submission
We prepare the forms, certificates, fee and documents and submit through the Planning Portal.
Officer liaison
We answer the planning officer and make any amendments within five working days, at no charge until approval.
Building regulations
Technical drawings are coordinated with the structural engineer's calculations, the drainage and the planning conditions.
Approval and hand-over
Building control approval, then a next-steps pack covering the commencement notice, party wall timing and CIL.
Free redraws until approval. Every drawing set is checked independently, and the checker is never the person who drew it.
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Merton grants most roofs but takes its time
Out of 759 householder decisions, 92.9% were granted, a figure that says applicants with proportionate schemes do well. The timing figure is the weaker one: 85.2% decided on time, which leaves a real share running past the target.
For an owner that matters more than the percentage suggests. A builder booked for an early start can wait weeks for the decision, and a loft has no value to anyone while the roof is open. We build the programme with the decision date as the start, not the other way round, and we do not quote a start before the council has decided.
The most effective way to avoid delay is a complete application. Our planning drawings in Merton page lists the sheets, and we add a street-scene elevation and a section through the junction of the two roofs so the case officer does not need to ask.
Local figures for Merton
| Measure | Value | Period | Source |
|---|---|---|---|
| Householder applications granted | 92.9 % | 1 July 2025 - 30 June 2026 | assets.publishing.service.gov.uk |
| Householder applications decided in time | 85.2 % decided within 8 weeks or an agreed extended period | 1 July 2025 - 30 June 2026 | assets.publishing.service.gov.uk |
| Householder decisions | 759 decisions | 1 July 2025 - 30 June 2026 | assets.publishing.service.gov.uk |
| Conservation areas | 28 named conservation areas published by the council | — | planning.data.gov.uk |
| Listed building entries | 243 list entries (Historic England, within the LPA boundary) | — | planning.data.gov.uk |
| Heritage at Risk entries | 23 Heritage at Risk Register entries within the LPA boundary (Historic England) | — | planning.data.gov.uk |
| Domestic gardens share of land (GLUD 2005) | 27.2 % of land that is domestic garden (GLUD 2005) | 2005 | data.london.gov.uk |
| Mayoral CIL rate (indexed) | 72.73 £/m² (indexed, permissions granted in 2026) | — | london.gov.uk |
| GPDO 2015 Sch 2 Pt 1 Class B, para B.1(d) | 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume | — | legislation.gov.uk |
A blank value means the figure has not been published, not that there are none. Check your own address with the council.
Householder applications by street in Merton
| Street | Applications | Approved |
|---|---|---|
| South Park Road | 26 | 96% |
| Lower Morden Lane | 25 | 84% |
| Coombe Lane | 23 | 83% |
| Pepys Road | 23 | 77% |
| Palmerston Road | 21 | 100% |
| Dorset Road | 20 | 72% |
| Marryat Road | 20 | 94% |
| Mostyn Road | 20 | 89% |
| Springfield Avenue | 19 | 95% |
| Vineyard Hill Road | 19 | 100% |
| Claremont Avenue | 18 | 88% |
| Queen's Road | 18 | 100% |
| Faraday Road | 17 | 82% |
| Gladstone Road | 17 | 60% |
| Stroud Road | 17 | 94% |
Loft enlargement in section: the permitted development limits
A dormer on the rear slope, with the limits that decide whether it needs planning permission.
- A · Extra roof volume allowed
- 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume
- B · Set-back from the eaves
- Original eaves maintained; enlargement set at least 0.2 m from the eaves measured up the roof slope, so far as practicable (not required for hip-to-gable or roofs joining a rear/side extension)
- C · Height limit
- No part higher than the highest part of the existing roof
The Merton documents we read for an L-shaped dormer
The Merton Local Plan 2024 was adopted in 2,024. Supporting it, the council lists the Borough Character Study SPD and a Small sites toolkit SPD, alongside the Basement and subterranean SPD. None is a dormer guide as such.
We therefore draw from the plan's design policies and the character study, which together tell us how the council reads a roof in its setting. Merton has 28 conservation areas, and inside them a roof enlargement is not permitted development.
Historic England lists 243 entries in the borough and 23 appear on the Heritage at Risk Register. A listed house needs consent that we do not draw on this site, and we say so at the start. If your house sits beside a listed building or inside a conservation area boundary, we photograph the rear roofs nearby so the drawings can show how the L relates to them.
Where an L fits in Merton
Where a Merton house has a rear wing, an L-shaped dormer can give it a second room and a stair that is not squeezed. Domestic gardens cover 27.2% of the borough's land in the national land-use database, so the new roof will be seen from several houses.
The national volume rule still sets the limit: 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume. We measure the roof on survey day and subtract earlier loft work before sketching the shape.
If the L exceeds the allowance, a smaller dormer, a hip-to-gable or a planning application are the options, and we price them side by side. Because the council is slower than its grant rate suggests, a design that fits permitted development and a certificate can save more time than it appears to save in fees. We keep that in the comparison, so you see months as well as pounds. A realistic programme also allows for the survey, the drawings, the structural design, the party wall notices and the decision, and we set them out in order on one page when we send the quote, so you can see where the time goes.
Levy and costs to expect
Merton also charges its own levy, which we read from the council schedule for the address, and the Mayor of London adds 72.73 pounds per square metre this year. A conversion inside the existing roof usually adds no chargeable area, so levy is rarely the main cost.
The larger costs are structural steel at the junction of the two roofs and the party wall process. We prepare the drawings so the engineer and surveyor can work from one set. Where Merton asks for extra information after validation, our drawings already include the section and street elevation, which is the usual request, so the clock does not stop twice.
Compare roof options and nearby boroughs
For a plainer roof, see dormer loft conversion drawings in Merton, and for stairs and fire protection read loft conversion drawings in Merton. The borough overview is architectural drawings in Merton, and next door you can compare L-shaped dormer drawings in Sutton.
What you receive
Related pages
Other services in Merton
Questions
How long does Merton take to decide a householder application?
In the latest year 85.2% were decided within eight weeks or an agreed extension. Because the rest ran longer, we advise against booking a builder before the decision.
Is Merton likely to grant an L-shaped dormer?
The council granted 92.9% of householder applications in the latest year. That is a borough figure and not a forecast for your roof.
Does Merton have a dormer guide?
Its supporting documents include the Borough Character Study SPD. We found no separate dormer guide, so we draw from the plan policies and the character study.
Sources and dates
- assets.publishing.service.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- data.london.gov.uk, retrieved
- london.gov.uk, retrieved
- legislation.gov.uk, retrieved
- merton.gov.uk, retrieved
- merton.gov.uk, retrieved
- Contains public sector information licensed under the Open Government Licence v3.0.
- Contains OS data © Crown copyright and database right 2026.
- Contains HM Land Registry data © Crown copyright and database right 2026. This data is licensed under the Open Government Licence v3.0.
- Contains Historic England data © Historic England 2026. Contains Ordnance Survey data © Crown copyright and database right 2026.
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We check the constraints, then send a fixed fee. Messages before 3pm get a reply the same working day.