Small granny annexes: under 25sqm
A small granny annexe, under 25sqm, is usually one room with a shower room behind its own door: a studio with a kitchenette, or a garden bedroom with no kitchen at all. It is about the size of a large garden room, built to a residential standard so that someone can sleep and live in it.
Illustrated from a scale model by The Garden Room & Annexe Guide.
In short
- Layout: a studio with living, kitchenette and bed in one room, or a garden bedroom with an en-suite and no kitchen. A few use internal walls to make a separate bedroom.
- What fits: a double bed, a kitchenette, a wardrobe and a shower room fit in about 21sqm, such as a 6m × 3.5m building.
- Cost: compact studios typically cost £50,000–£75,000 for the building, and £65,000–£95,000 with groundworks and connections.
- Planning: size makes no difference: 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 an annexe under 25sqm?
At this size every layout comes down to one main room and a shower room. What changes is whether the room has a kitchen, and whether the bed shares the room with it.
- Studio annexe · around 20–25 sqm
- Living, kitchenette and bed in one room, with the shower room behind the only internal door. Ark Design Build’s 19.84sqm annexe in Esher fits a kitchenette and an en-suite beside the main room, and Executive Garden Rooms’ 21.5sqm compact granny annexe does the same for one person.
- Garden bedroom · usually under 25 sqm
- A bedroom and an en-suite shower room, with no kitchen. It suits guests, or a relative who eats and spends the day in the main house, such as Executive Garden Rooms’ 6m × 3.6m en-suite garden bedroom in Dorset.
- Divided plan · 20–25 sqm
- Internal walls make a small separate bedroom. Annexe Spaces’ 6m × 3.3m one-bed annexe in Sutton has a shower room, a kitchen-living area and a bedroom, and Timeless Garden Rooms’ 6m × 3.5m student den fits three rooms.
Footprint and floor area are not the same. Sizes are usually quoted as the external footprint. Residential walls are thick, so the usable floor inside is typically 15–20% smaller, and at this size that is the difference between a sofa and no sofa.
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Small annexes under 25sqm built by UK companies
Every annexe under 25sqm 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.
Small Granny Annexe
A compact 19.84sqm granny annexe in Esher maximises space with clever design. The mono-pitched building features a multi-functional living area, kitchenette and en-suite, enhanced by corner glazing and a roof window for natural light.
En-Suite Garden Bedroom
This en-suite garden bedroom by Annexe Spaces provides a functional, stylish extension alternative, featuring a low-maintenance Silicon K-Render finish. The design includes a spacious bedroom and shower room with new-build interiors, creating seamless indoor-outdoor living.
Garden Bedroom with En Suite
A 6m x 3.6m en-suite garden bedroom in Dorset was built by Executive Garden Rooms. The turnkey project includes design, utility connections, and planning management. The well insulated annexe features wrap-around glazing and a spacious shower room.
One Person Granny Annexe
Executive Garden Rooms designed a 6m x 4m one-person granny annexe, showcasing a compact yet functional home. It features a combined living/sleeping area, kitchen with instant hot water, and a spacious shower room. The sedum roof adds insulation and visual appeal.
Compact One Bed Annexe by Annexe Spaces
A 6m x 3.3m one bed annexe in Sutton by Annexe Spaces. Rather than leaving it open plan, walls are used thoughtfully to define a shower room, kitchen living area and bedroom, with extra height adding space.
Student Den in the Garden
Timeless Garden Rooms designed this stylish student den with a modern mono-pitch roof, Larch cladding, and custom sliding doors. The 6m x 3.5m space features three rooms: two living areas and a shower room, offering privacy and practicality for a university student.
Boutique Garden Bedroom with Ensuite
Timeless Garden Rooms crafted a boutique garden bedroom with an ensuite, blending hotel-style luxury with bespoke design. Featuring a Cedar shingle roof, green cladding, and a panelled feature wall, this Isle of Wight project offers elegant, guest-ready accommodation.
Compact Granny Annexe
Executive Garden Rooms created a compact 21.5 square metre granny annexe for single occupancy. It includes an open-plan bedroom/lounge with a kitchenette and a well-equipped shower room. Clad in low-maintenance Cedral weatherboard, this turnkey project meets full planning and regulatory standards.
Frequently asked questions
- What is the smallest granny annexe?
- The smallest self-contained annexe on The Guide is a 19.84sqm studio in Esher with a kitchenette and an en-suite shower room. Garden bedrooms without a kitchen can be smaller still. Below about 20sqm it becomes hard to fit a double bed, a kitchen and a shower room in one building.
- Can you fit a double bed, a kitchen and a bathroom in 20–25sqm?
- Yes. A studio of around 21sqm, such as a 6m × 3.5m building, takes a double bed, a kitchenette along one wall and a shower room across one end. The furniture has to be planned carefully, and the internal floor area is smaller than the footprint.
- How much does a small granny annexe cost?
- A compact studio annexe under 25sqm typically costs £50,000–£75,000 for the building. With groundworks and utility connections, a realistic budget is around £65,000–£95,000. Whether VAT is included depends on the planning route.
- Does a small annexe need planning permission?
- Yes. Size makes no difference: a building with its own kitchen, bathroom and sleeping space needs full planning permission with Building Regulations, or the Caravan Act route with a Lawful Development Certificate. Sleeping accommodation also needs Building Regulations approval, even without a kitchen.
Find 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.
