Garden annexes 35 to 45sqm
Most one-bedroom granny annexes are between 35 and 45sqm. At this size there is room for a full kitchen, a living area that is separate from the bedroom, and a bedroom with space for a wardrobe.
Illustrated from a scale model by The Garden Room & Annexe Guide.
In short
- Layout: mostly one-bedroom annexes. Some stay open-plan for accessibility, and the smallest two-bedroom annexes start at around 41sqm.
- Footprint: 8m × 5m (40sqm) is the most common footprint among the projects on this page.
- Cost: one-bedroom annexes of 35–45sqm typically cost £85,000–£110,000 for the building, and £100,000–£130,000 all-in.
- Planning: a self-contained annexe needs full planning permission with Building Regulations, or the Caravan Act route, built to BS3632 with a Lawful Development Certificate. See planning and the Caravan Act route.
What fits in a 35 to 45sqm annexe?
A full kitchen and a generous living area, with the bedroom behind its own wall. The building is usually long enough for the bedroom to sit at one end, away from the front door.
- One-bedroom · often 8m × 5m
- A bedroom, a shower room and a kitchen-living area. Swift Unlimited’s 8m × 5m annexe, Annexe Spaces’ 8m × 5m SIPs annexe in Scotland and Executive Garden Rooms’ 8m × 5m annexe for a young family member all use this footprint.
- Open plan · 35–40 sqm
- Some owners keep one large room. Timeless Garden Rooms’ 40sqm teenagers’ den has a raised sleeping deck, and Ark Design Build’s 7.5m × 5m garden apartment uses fitted furniture to define the zones.
- Two bedrooms · from around 41 sqm
- The smallest two-bedroom annexes on The Guide are Vagabond Haven’s 41sqm Evergreen, with a single second bedroom, and JML Garden Rooms’ 44sqm holiday lodge.
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Annexes of 35 to 45sqm built by UK companies
Every annexe of 35 to 45sqm featured on The Guide, in a random order. Each one links to the full write-up, with the floor plan and the company that built it.
An 8m x 5m One-Bedroom Garden Annexe by Swift Unlimited
An 8m x 5m one-bedroom garden annexe by Swift Unlimited, built as a second building for returning clients. The 40sqm plan holds a 9sqm bedroom, en-suite shower room, and an L-shaped living space with a kitchen and breakfast bar.
Self-Contained Teenager’s Den in the Garden
This 40sqm garden annexe by Timeless Garden Rooms offers teenagers a private, adaptable retreat while staying close to home. Featuring a bespoke interior, a kitchenette, a shower room, and a sleeping deck, it blends functionality with aesthetic appeal, providing family entertainment and guest space.
A Uniquely Shaped Mobile Home Slots into the Garden
A Room in the Garden designed a wedge-shaped mobile home annexe for an irregular garden. The bespoke design maximises space, featuring a kitchen, living area, bedroom and shower room. Its unique shape and tailored design demonstrate innovative solutions for challenging spaces under Caravan Act regulations.
SIP’s Granny Annexe
Annexe Spaces built an 8m x 5m SIPs granny annexe in Scotland. The one-bedroom home includes a bright living area, well-equipped kitchen, and modern shower room. Highly insulated for comfort and efficiency, the project covered planning, groundworks, and utility connections, offering a comprehensive solution.
Open-Plan Garden Annexe in Surrey
Miniature Manors delivers a turnkey service for garden annexes, managing every detail from design to completion. This Surrey project features an 8.7m x 4.4m open-plan living space with Millboard cladding, bi-fold doors, and a bespoke Shaker-style kitchen for seamless modern living.
One Bedroom Granny Annexe with Well-Equipped Kitchen
This stylish one-bedroom granny annexe by Executive Garden Rooms includes a large L-shaped kitchen, perfect for a keen cook downsizing. Measuring 8m x 4.5m, it includes a light-filled living space with sliding doors and a Velux window with rain sensors.
Garden Apartment for a Long Garden
A 7.5m x 5m garden annexe creates a modern studio apartment in the middle of a long garden. The design features bi-fold doors at both ends, fitted furniture, high-spec kitchen and shower room, maximising space while maintaining garden views.
36sqm One-Bedroom Garden Annexe
This Swift Unlimited 36sqm one-bedroom garden annexe highlights their collaborative, bespoke approach. Designed to maximise garden space, it features an L-shaped layout, tailored kitchen, pocket doors, built-in storage, and an ensuite, providing independence and comfort close to family.
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Frequently asked questions
- What size is a one-bedroom granny annexe?
- Most one-bedroom annexes on The Guide are between 35 and 45sqm, and 8m × 5m (40sqm) is a common footprint. Compact one-bedroom annexes start at around 30sqm, and larger ones run to 55sqm.
- Can you fit two bedrooms in a 40sqm annexe?
- It can be done, but something gives. The smallest two-bedroom annexe on The Guide is 41sqm, with a double bedroom and a single second bedroom. A comfortable two-bedroom annexe is nearer 55–60sqm.
- How much does a 40sqm annexe cost?
- A one-bedroom annexe of 35–45sqm typically costs £85,000–£110,000 for the building, with a realistic all-in budget of £100,000–£130,000 once any groundworks and connections not in the price are added. Whether VAT is included depends on the planning route.
Find one-bedroom annexe specialists that cover your area
The Garden Room & Annexe Directory lists UK annexe specialists, filtered by location, planning route and design approach.
Last updated October 2026 · Part of our garden annexe guide.
