Dormer in Merton: Planning Permission Guide
A guide to dormer extensions in Merton — PD rules, costs, and what you need to know.
Check if your dormer qualifiesDormers in Merton at a glance
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Merton has conservation areas including Wimbledon Village, Wimbledon Common, Mitcham Cricket Green, and Cannizaro Park. Listed buildings cluster around Wimbledon Common and Merton Abbey Mills. Wimbledon Common is Metropolitan Common Land with its own byelaws near the edges. Article 4 Directions cover parts of Wimbledon Village. The borough has a mix of affluent Edwardian housing around Wimbledon and Victorian terrace stock in Mitcham and Colliers Wood.
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Permitted Development Rules
Additions etc to the roof of a dwellinghouse
GPDO 2015, Schedule 2, Part 1, Class B
Dormers are covered by Part 1, Class B of the GPDO alongside other roof additions. They're subject to volume limits and restrictions on which roof slopes they can face.
Key dimension limits
These are the maximum GPDO limits for a detached house with no constraints. Your actual limits depend on your property type, location, and any planning restrictions.
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Check my limitsWhich Professionals Do You Need?
Dormer construction involves significant structural work to your roof, so professional design and engineering input is recommended.
You'll need a structural engineer and a party wall surveyor for this project.
Loft conversions involve structural alterations and Building Regulations requirements that benefit from professional design.
Typical fee: £2,000–£5,000 (Plans + Building Regs)
Loft conversions require structural calculations for floor strengthening, roof alterations, and any steelwork.
Typical fee: £800–£2,500
Your semi-detached house shares a boundary with neighbours. Extensions and loft work within 3 metres of a shared wall trigger the Party Wall Act.
Typical fee: £700–£1,500 (per neighbour)
This guidance is based on a typical semi-detached house with no special constraints. Listed buildings, conservation areas, and attached properties may require additional professional input.
Find out exactly which professionals you need for your dormer.
Get personalised guidanceConservation Areas & Listed Buildings
In conservation areas, dormers facing a highway are not permitted development. Rear dormers may still be possible if they meet the volume limits.
Properties in conservation areas often have reduced permitted development rights. Some project types (like side extensions) lose PD rights entirely. An Article 4 Direction can remove additional PD rights.
Listed buildings (Grade I, II*, or II) have no permitted development rights at all. Any external alteration requires Listed Building Consent in addition to any planning permission. An architect experienced in heritage work is essential.
Check if your property is in a conservation area or has other planning constraints.
Check my propertyFrequently Asked Questions
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