Garage in Harrow: Planning Permission Guide
A guide to building a garage in Harrow under permitted development — rules, costs, and professional advice.
Based on 46 decided applications in Harrow over 12 months (39 granted, 7 refused).
Harrow has conservation areas around Harrow-on-the-Hill (a distinctive hilltop village with very strict design controls), Pinner, and Stanmore. Listed buildings are concentrated in Harrow-on-the-Hill and around Harrow School. Green Belt borders the north and west of the borough around Stanmore Common and Harrow Weald. Article 4 Directions cover parts of Harrow-on-the-Hill. The borough has a mix of inter-war semis, garden suburb character, and older village cores.
Personalised odds
5 nearest comparables & refusal reasons for your address.
Get my report — £9See a sample →Recent garage decisions in Harrow
The 5 most recent decided applications. Addresses redacted to postcode area.
Certificate of Lawful Proposed Development: Conversion of garage to habitable room, Replace garage door with window in front elevation
Detached garage to front; landscaping
Conversion of garage into habitable room; replacement of garage door with window
Change of use: Garages / storage to Pilates Studio (Class E) on ground floor; single storey front extension; external alterations
Variation of condition 2 (Approved Plans) attached to planning permission PL/2458/25 dated 25/11/2025 to allow design changes to the gara…
These are borough-wide. See the 5 nearest to your address.
Get my report — £9Permitted Development Rules
Buildings etc incidental to the enjoyment of a dwellinghouse
GPDO 2015, Schedule 2, Part 1, Class E
Garages fall under Part 1, Class E of the GPDO (the same class as outbuildings). They must be incidental to the enjoyment of the house.
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.
Enter your postcode to see the personalised limits for your garage.
Check my limitsTypical Costs in London
Garage costs depend on size, whether it's attached or detached, and whether it includes electrics or additional rooms above.
Cost per m²
construction rate
Typical total
Based on 15–20 m²
Typically includes
Typically excludes
Single garage. Double garages and garages with rooms above will be significantly more.
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Get my estimateWhich Professionals Do You Need?
A standard single garage can often be built from supplier designs. A garage with rooms above will need architectural and structural input.
A draughtsperson or architectural technician can prepare any drawings needed. A full architect may not be necessary.
Garden buildings and garages can often use supplier designs or simple drawings from a draughtsperson.
Typical fee: £500–£2,000 (Basic drawings)
A structural engineer may be needed if the garage has a room above or connects to the house.
Typical fee: £500–£1,500
May apply if the work is within 3 metres of a shared boundary. Check with your builder.
Typical fee: £700–£1,500 (per neighbour (if applicable))
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 garage.
Get personalised guidanceConservation Areas & Listed Buildings
In conservation areas, garages are subject to the same Class E rules. Consider using materials sympathetic to the area character.
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
Just want a quick yes/no for your garage?
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