Can I rent out a garden annex?

This depends on your planning permission conditions. Some approvals restrict use to 'ancillary' accommodation for family only, while others permit independent letting. We recommend discussing your intentions with your installer at the feasibility stage.

How much does a garden annex cost?

Garden annexes typically start from £65,000 and range to £120,000+ depending on size, specification, and finishing level. While this is more than a standard garden room, it's significantly less than a traditional extension or buying additional property.

Northwood · Middlesex

Garden Annexes in Northwood

Serving the London Borough of Hillingdon planning area · Northwood (Metropolitan line)

Northwood's large detached homes on generous plots are among the best-suited properties in the Hillingdon area for a premium garden annexe build. Self-contained annexes with full kitchen, bathroom, and separate utility connections are delivered from £65,000 under Hillingdon Council planning, adding between £40,000 and £95,000 to properties that senior professionals and business owners choose for their space and quality of life.

0.15

U-value

£40,000–£95,000

Value uplift

25–40 days

Build time

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Garden Annexes in Northwood

Northwood sits within Hillingdon's jurisdiction, and our local knowledge of the planning landscape here ensures a smooth process for self-contained habitable garden annexe builds. The large detached homes on generous plots in this upmarket Middlesex suburb bordering Hertfordshire area accommodate the footprint comfortably, while senior professionals and business owners here are motivated by creating independent living space for family members, guests, or rental income. Standard specification includes full Building Control compliance, kitchen and bathroom plumbing, separate utility connections, and fire-rated construction.

Provide comfortable, independent living space for family members with a self-contained garden annex. Perfect for elderly relatives (Granny Annexes), young adults needing independence, guest accommodation, or even rental income. Our recommended installers build fully habitable homes to building control standards, complete with kitchens, bathrooms, and living areas. They offer a cost-effective alternative to care homes, house extensions, or buying a separate property.

Planning Authority: London Borough of Hillingdon

Northwood falls within Hillingdon's planning area. No significant conservation restrictions apply across most of Northwood's residential streets, though some tree preservation orders (TPOs) on mature garden specimens may affect foundation positioning. Your installer will identify any TPOs at the site survey.

Why Choose This?

Keep family close while maintaining independence and privacy

Cost-effective alternative to care homes or house extensions

Increase your property value significantly

Faster construction compared to traditional building extensions

Potential rental income stream (subject to planning)

2026 Technical Specification

Full kitchen and bathroom installation

Building Control compliant construction

Accessible design options (ramps, wet rooms, wide doorways)

High-performance insulation exceeding Part L requirements (U-value 0.15 W/m²K)

Separate utility connections and metering

How It Works

Feasibility Assessment

Check planning viability, site suitability, and building control requirements for habitable space.

Planning Application

Full management of the planning permission process, including design and submit documentation.

Building Control

Ensuring all regulations for habitable space are met, including fire safety and accessibility.

Complete Construction

Full build including all utilities, plumbing, electrics, and interior finishes.

Garden Annexes in Northwood — FAQs

Yes. Garden annexes intended for sleeping or living accommodation almost always require planning permission. Our partner installers manage the full application process on your behalf and can advise on the likelihood of approval in your specific borough.

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